INTERNATIONAL SOCIETY FOR MECHANICS AND

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This is an open-access database that archives thousands of papers published under the Auspices of the ISSMGE and maintained by the Innovation and Development Committee of ISSMGE. Heritage lecture: State of the art and development of geotechnical engineering in Conférence du patrimoine: L’état des connaissances et le développement de la géotechnique en Allemagne

W. Wittke - Institute for Engineering, Soil Mechanics, Rock Mechanics and Waterways Construction of Aachen Technical University, Germany Institut des Fondations, de la Mécanique des Sols et des Roches de la construction des voies navigables de l'Université Technique d’Aix-la-Chapelle, Allemagne

A BSTRA CT: The development of geotechnical engineering in Germany cannot be seen separately from the development in the neighbouring European countries, especially as far as the mathematical and mechanical foundations o f soil mechanics created as o f the 17th century are concerned. Due to the widespread use o f the among other things, there was a steady interchange o f scientific knowledge. An intensified development o f new construction methods in the area o f foundation engineering started in Germany with the growing industrialization in the 19th century and the resulting problems such as the increasing volume o f traffic. The definite establishment o f geotechnical engineering as an independent engineering discipline in Germany was achieved with the foundation o f numerous new scientific research institutes in the middle o f the 20th century. Today, many public and private institutions develop solutions for geotechnical problems in construction practice.

RESUM E: Le développement de la géotechnique en Allemagne ne peut pas être considéré séparément sans qu’on se rende compte du développement dans ses pays voisins européens. En p articulier, il faut mentionner les fondations mathématiques et mécaniques de la mécanique des sols à partir du 17ème siècle. Entre autres grâce à la langue allemande bien connue en Europe il y avait continuellement d’échange de savoir. Un développement plus intensifié des nouvelles méthodes de constructions dans le domaine des travaux de fondations a commencé en Allemagne pendant l’industrialisation en 19ème siècle et les problèmes qui en résultaient, par exemple à cause de la quantité du trafic augmentante. Le définitif établissement de la géotechnique comme une sp écialité de génie indépendante a pris lieu en Allemagne au milieu du 20ème siècle quand nombreuses institutions scientifiques étaient fondées. Aujourd’hui on y trouve plusieurs institutions publiques et privées qui se consacrent aux solutions pratiques des problèmes géotechniques.

1 INTRODUCTION Although the campaigns o f conquest took the Roman soldiers far into the north o f Germany, the larger military camp s were estab­ The beginnings o f foundation engineering in the area o f what is lished along the limes at, for example, what are to day the towns today the Federal Republic o f Germany are inseparably linked of Mainz (Mogontiacum), Trier (Augusta Treverorum) or Co­ with the Romans whose empire extended up to the lim es in Cen­ logne (Colonia Claudia area Agrippinensis). tral Europe in 155 A D (see figure 1). In order to provide the Roman settlements with water, water conduits were constructed, the largest of which was the Eifel conduit, which extended over a total length o f 88 km and pro­ vided Cologne with spring water from the Eifel mountains. The difference in altitude between the highest spring catchment in the Eifel and the water castle in Cologne amounts to only 400 m, resulting in an average gradient o f approx. 0.5 %. In order to gain an impression o f the dimensions o f this structure, it shall only be mentioned that 160000 m3 o f masonry and concrete had to be produced and 350000 m3 o f soil were moved. As late as the fifth century the Eifel conduit was in operation. Later, the stones were removed and used for other structures, such as convents and churches. Part o f this conduit were several aqueducts, parts o f which were reconstructed and can still be visited (Wolfel, 1997a). Numerous bridges over smaller and larger rivers were con­ structed for the Roman troops and for the transport o f supplies. The most famous of these bridges built by Roman engineers forces is the Caesar Bridge over the river , built in 55 BC, probably betw een what are today the towns o f Koblenz and An- demach (see figure 2). This bridge was describèd by JULIUS CA ESA R in his w ork "The Gallic W ar". Since, contrary to his normal habits, he does not mention the constructor o f the bridge, it is assumed that he himself designed this structure (WOlfel, 1997b). The tools and technical aids to work wood and to drive piles existed since the middle o f the first millennium BC. Construction o f the Caesar Bridge started with two piles 45 cm in diameter, which were driven into the ground at an angle in Figure 1. Roman limes (155 AD) (from: Putzger, 1974). downstream direction and subsequently joined with horizontal

2075 made to link the Danube with the Main and thus with the Rhine failed, since the differences in altitude proved to be too great. In those days, chamber locks were still unknown. Remnants o f this structure can still be seen as "Fossa Carolina" between Nurem­ berg and Donauworth. The first in Europe that surmounted a watershed is the Stecknitz canal near Lauenburg, constructed during the years 1391-1398 (Straub, 1964).

1 Longitudinal Beam 2 Transverse Beam 2 FUNDAMENTAL PRINCIPLES 3 2 Piles, 45 cm a 2.1 Mathematics, Technical Mechanics and Hydraulics Figure 2. Caesar Bridge over the river Rhine (55 BC ) (from: W olfel, 1997b). The increasing knowledge o f the theoretical princip les in civil engineering, especially geotechnical engineering, is closely con­ nected with the developments in the field o f mathem atics. As a combining element with the knowledge o f nature, it creates the principles o f the exact sciences o f physics and mechanics. In Germany and Europe, a fundamental turning point was reached during the Middle Ages when efforts were made to bring the principles o f reason and logical thinking into harmony with religious doctrine (Straub, 1964). However, due to the strictly philosophical nature o f the reflections, there were few connections to a practical application o f this know ledge. In ad­ dition, many laws o f nature that could now be mathematically described had been known intuitively to the practitioners for a long time. In the beginnings, it was mostly Italians as, for exam­ ^ - v * -T ple, LEONARDO DA VINCI (1452-1519) or GALILEO GA LILEI (1564-1642), who were advancing research in the field o f mechanics. Later, predominantly scientists from , Great Figure 3. Roman Bridge over the river Rhine near Mainz (1st Britain, , and Germany developed methods for the century A D) (from: W olfel, 1997b). description o f the mechanical behaviour o f bodies. The explana­ tion o f the problem o f bending attempted by GA LILEI already contains the important principle o f proportionality o f strains and stresses in an elastic body, which was formulated by ROBERT props. Next to them, a pair o f piles was driven in the same man­ HOOKE (1635-1703). This principle is the basis for the further ner, but in upstream direction. By means o f a 60-cm -thick hori­ development o f the classical theories o f strength o f materials and zontal prop, installed between the pairs o f piles, a trestle was elasticity. Initially, these findings were applied to bending created. For additional support respectively stabilization, another beams; later, solutions for continuum mechanics pro blems came two piles with a smaller inclination were subsequently driven. to the fore as well. Over these rammed trestles, spaced at 4 to 5 m, longitudinal With respect to German scientists, GOTTFRIED W ILHELM beams were mounted as a superstructure (W olfel, 1997b). LEIBNIZ (1646-1716) has to be named first, who not only The first wooden bridge on masonry pillars over the river Rhine worked in the fields o f mathematics, history, jurisprudence and was constructed in the first century A D, during the reign of Em­ theology, but also on questions of mechanics and strength o f peror VESPASIA N (69 to 79) between Mogontiacum (Mainz) materials. Due to his work on the Brunsw ick mines, he also en­ and its fortress. The only picture o f this bridge o ver the Rhine countered geotechnical practitioners. ("FL REN US") is on a leaden locket found in the river Saone Together with ISAAC NEWTON (1642-1727), LEIBNIZ is near Lyon (see figure 3).The advantage o f a bridge on stone pil­ considered the founder o f the infinitesimal calculus, which both lars was longer life since wooden piles were rotting fast in water. succeeded in discovering at the same time, but independently o f Normally, the stone pillars had a concrete filling within a casing each other. The two scientists chose a somewhat different ap­ o f cut stones. Over these pillars, the wooden bridge was then proach, insofar as LEIBN IZ succeeded in his findings by philo­ constructed. The prerequisite for the construction o f stone pillars sophical and logical reasoning and geometric reflections, was the development o f concrete hardening in water. The stone whereas NEW TON worked on specific dynamics and kinematics pillars o f the Rhine bridge near Mainz were each erected on an problems. With the revolutionary new arithmetical method of oak pile grate (W olfel, 1997b). differential and integral calculus, mathematics was no longer Around 800, CHA RLEMA GNE (742-814) tried to reconstruct considered merely a tool, but a stimulus for the exact sciences it after it had been severely damaged, but the construction was (Straub, 1964). never completed (W olfel, 1997b). The bridge was finally de­ With respect to the development o f the methods o f infinitesi­ stroyed in the late Middle Ages. mal calculus, the Basle mathematicians LEONHARD EULER (1707-1783) and the BERN OULLI family have to be mentioned. Around the year 140, another bridge made o f wood and stone In the search for examples o f applications, solutio ns for me­ was constructed, crossing the Moselle in Augusta Treverorum chanics problems were found that only later gained practical (Trier). The stone pillars, still in existence today, were founded importance in civil engineering. Among the problems solved directly on the exposed rock in the dry inside o f box cofferdams (W olfel, 1997b). with infinitesimal calculus, the investigation of elastic lines The most significant application of foundation engineering (now: bending curves) should be emphasized. JAKOB during the Middle Ages was the foundation o f churches. As a BERNOULLI (1654-1704) and LEONHARD EULER were the rule, these were carried out as individual foundations, by wid­ first to find and describe the real nature o f the elastic line, 50 ening the lower ends o f the pillars. In difficult, i.e. non-bearing years before the Frenchman CHARLES AUGUSTIN DE ground as, for example, in the case o f the cathedrals in Aachen COULOM B (1736-1806) found the final solution to the problem and Cologne, driven wood piles were used to support the foun­ o f bending (Straub, 1964). dation. Their number, however, was still chosen arbitrarily or EULER, who worked at the newly founded Academy o f Sci­ based on previous experience (Straub, 1964). ences in from 1741 to 1766, published a treatise on the Furthermore, the water and canal structures o f the Middle plane elastic lines in 1744, giving differential equations for nine Ages should be mentioned here. The efforts CHARLEMA GNE different cases. He used the minimum principle in his treatise.

2076 DANIEL BERNOULLI (1700-1782) had already found out that as infinitesimally small points. The forces acting on the particles a beam assumed the shape corresponding to the minim al bending were supposed to depend on their mutual distance. N AVIER work. This can be considered as the first suggestio n o f the law o f supposed that the inner forces are in equilibrium before a body is minimal deformation work. The method o f variation calculus, deformed. He only considered their increase or decrease. Fol­ later developed by EULER and JOSEPH LOUIS COMTE DE lowing HOOKE’s law, these stress changes were assumed pro­ LAGRA NGE (1736-1813), made it possible to find the function portional to the changes in particle respectively m olecular dis­ for which a specific characteristic obtains a maxim um or mini­ tance. mum, using the method o f differential calculus, and taking into The French engineer AUGUSTIN LOUIS CAUCHY (1789- account stipulated boundary conditions. JOHANN BERN OULLI 1857) obtains the tension by summing up the individual actions. (1667-1748), brother o f JA KOB BERNOULLI, formulated the CA UCHY then considers the stresses acting on an infinitesimal principle o f virtual deformations. Furthermore, decisive contri­ element conceived to be cut out of the body, a tetrahedron for butions to the theory of ideal fluids were made by DANIEL example, and then establishes the equilibrium conditions for this BERNOULLI and his father JOHANN. In 1750, LEONHARD element. The most important finding by CAUCHY was pub­ EULER was the first to find an explicit formulation o f the basic lished in 1822. In this publication, he describes the dependency law o f dynamics for a differential body element (De Boer, 1988). o f the stress vector on the orientation o f the respective section The variation calculus was also the basis for the theory of plane by means o f a simple linear transformation. This transfor­ earth pressure, developed by COULOMB. COULOMB was the mation is expressed by a stress tensor that only varies with the first to consider the soil mass as a one-component continuum. considered location and links the stress vector to the section Unlike the other 18th century scientists such as EU LER and the plane unit vector. This was the prerequisite for the formulation BERN OULLI family, COULOM B was also an engineer. He was o f the basic equations o f the theories o f viscous fluids and solid searching for solutions to problems in structural analysis and bodies (De Boer, 1988). strength o f materials with respect to the application in construc­ The description o f the mechanical behaviour o f viscous fluids tion practice. In his publication o f 1773, he presents the final began with a publication by NAVIER in 1822. In 1834, the solutions to the bending beam, a failure hypothesis for masonry Frenchman BA RRE DE SAINT-VENANT (1797-1886) intro­ under compression, as well as the well-known method to calcu­ duced the equations o f motion of viscous incompressible fluids. late the earth pressure. Further contributions to the theory o f viscous fluids were made by, amongst others, the German GOTTHILF HEINRICH LUDW IG HAGEN (1797-1884), the English physicist and engi­ F t y . 4 ° neer OSBORN REYNOLDS (1842-1912), as well as LUDWIG PRANDTL (1875-1953). PRANDTL, who was bom in Freising, Bavaria, worked later in Gottingen as a professor. Today, PRANDTL is considered the founder o f modem fluid mechan-

HENRY PHILIBERT GASPARD DARCY (1803-1850), who worked, amongst others things, as senior engineer o f the City o f Paris, was the first to investigate the interaction of solid body skeleton and fluid. Based on tests, DA RCY developed the law describing the discharge velocity o f a fluid in a porous body by a linear function o f the pressure gradient. Furthermo re, ARSENE JULES ETIENNE JUVENAL DUPUIT (1804-1866) should be mentioned, who also worked in Paris as an engineer and estab­ lished the "well formula" based on DA RCY’s law, as well as LEWIS FRY RICHARDSON (1881-1953) and PHILIPP FORCHHEIMER (1852-1933), who solved specific boundary condition problems o f seepage flow (De Boer, 1988).

2.2 Earth Pressure Theory

COULOMB'S earth pressure theory is based on the observa­ .Fy.U tional finding that an earth prism o f about triangular shape de­ taches itself from the remaining ground and attempts to push aside a . The size and shape o f the earth prism are not exactly defined. Using variation calculus, COULOM B varies

Figure 4. Structural engineering problems according to COULOMB (from: Coulomb, 1773).

The Frenchman LOUIS MARIE HENRI NA VIER (1785-1836) was able to calculate the elasticity o f a beam, which JA KOB BERNOULLI and LEONHARD EULER considered as a con­ stant, from the shape o f the beam’s cross section and the elastic­ ity o f the material. Just like his compatriot SIMEON DENIS POISSON (1781- 1840), N A VIER shared N EW TON’s supposition, that the small­ est particles of a material influence each other. The Italian mathematician RUGGERO GIUSEPPE BOSCOVICH (1711- 1787) was the first to explain cohesion and elasticity o f solid Figure 5. Earth Pressure Theory according to COULOM B bodies with molecular forces. He assumed the smallest particles (1773).

2077 the dip angle o f the sliding surface o f the soil body and investi­ After his studies in Paris and Karlsruhe, KA RL CULM ANN, gates the minimum and maximum limit values o f the earth pres­ bom in the Rhine-Palatine, had been working at first in the fields sure that only just allow for downward sliding resp. upward o f railway and bridge construction. In 1855, he became professor sliding. The active earth pressure corresponds to the maximum at the Swiss Polytechnic (Eidgenössisches Polytechnikum) in o f the limit values for downward sliding and the passive earth Zurich, where he wrote the major part o f his publications. pressure to the minimum o f the limit values for upw ard sliding. The Scotsman WILLIAM JOHN MACQUORN RANKINE For the description o f the existing in the failure (1820-1872) used CA UCHY’s findings on earth pressure calcu­ plane, COULOM B used friction and cohesion as material con­ lation. He transferred COULOMB’S approach to the three- stants in his calculations (Straub, 1964). dimensional stress-deformation state. In his work o f 1856, Slope failures had been observed before and failure processes, RANKINE only considered non-cohesive, granular and, where parts o f a body slide on one another, had been known for without giving reasons for it, assumed planes o f failure whose some time. However, before COULOM B, it was not yet possible normal vectors lie in the plane o f the maximum and minimum to calculate failure states in advance, since the p rinciples o f the principal stress (De Boer, 1988). The failure condition derived mechanics of solid bodies had not yet been developed. The on this basis is a special case o f the MOHR-COULOMB failure stimulus for further progress in this direction cam e from the sec­ criterion, which was completed in 1900 by OTTO MOHR tion principle formulated later by EULER. In the beginning, a (1835-1915). section force vertical to the section plane was assumed, until in 1713 the Frenchman ANTOINE PARENT (1666-1716) intro ­ duced an additional tangential section force (De Bo er, 1988). COULOMB limited the tangential component o f the section force in the sliding plane o f the soil body. This limitation was brought about by a stress-independent material strength, the co­ hesion, and by frictional resistance. Under the assumption of these strength parameters, inner friction and cohesion, COULOM B also performed structural analyses o f masonry pil­ lars under compression and vaults. In summary, it can be said that COULOMB was the first to solve problems directly con­ cerning civil engineering with scientific methods. In contrast to COULOM B’S theory, which uses a friction co­ efficient, the director o f constructions o f the harbour, RE IN HARD WOLTMANN (1753-1837) introduced a friction angle in his earth pressure theory, w hich he developed independ­ ently o f COULOMB and published in 1794. This was based on his observations o f a relationship between the frictional coeffi­ cient and the slope angle o f a granular material. The introduction o f the friction angle has essentially contributed to the later de­ velopment o f the graphical methods (De Boer, 1988). Figure 7. MOHR circle (1871) and MOHR-COULOMB failure The findings o f COULOMB and also WOLTMANN are lim­ criterion (1900) (from: Terzaghi, 1954). ited to special boundary conditions, and, as opposed to EULER’s work on ideal fluids, they do not represent a complete continuum mechanics description. What was missing was the concept o f the OTTO MOHR was bom in Holstein and taught in Stuttgart stress tensor forming a tensor field. This was only introduced in (1868-1873) and Dresden (1873-1900). By means o f his method 1822 in the already mentioned contribution by CAUCH Y (De o f graphic representation o f a stress state (MOHR circle), he Boer, 1988). showed, that in COULOM B’S method, the orientation o f the Based on the findings by COULOMB, KARL CULMANN failure surface depends on the friction angle and the principal (1821-1881), who is considered the founder o f graphical struc­ stress directions, but not on the cohesion. In a publication o f tural analysis, developed in 1866 a graphical metho d to deter­ 1871, he also proved graphically that the shear stresses reach a mine the earth pressure. In this method, the calculations o f the maximum on the planes parallel to the direction o f the interme­ CO ULOM B method are largely substituted by a drawing. diate principal stress, and that, in agreement with the assumption made by RANKINE, failure occurs on these planes (De Boer, 1988; Dietrich, 1985). The Frenchman JOSEPH VALENTIN BOUSSINESQ (1842- 1929) enhanced the findings o f RA NKINE by the possibility to account for the wall friction o f a retaining wall (1876, 1885). Further improvements to the classical earth pressure theory were achieved by the Germans EMIL W INKLER (1835-1888) and FRIEDRICH EN GESSER (1848-1931). In a treatise, which he submitted in 1878 and which was published in 1880, EN GESSER introduced his geometrical theory o f earth pressure, which he found to be equivalent to the analytical method by W INKLER (1872). He also found out that in a comparison of earth pressure theory and earth pressure tests, the difficulty is to determine in the test, at what point the limit equilibrium state is reached (Dietrich, 1985). Furthermore, the graphical methods of the Frenchman PONCELET (1840) and the Austrian

S REBHA NN (1871) for determining the earth pressure should be 1 Slope Line 2 Slip Line max. Ea mentioned here. 3 max. Ea 4 Slip Line min. Ep In contrast to COULOMB, FRITZ W ILHELM FERDINAND 5 min. Ep KOTTER (1857-1912), who was bom in Berlin and later taught as a professor at the Berlin Academy o f Mining, tried to capture the magnitude and distribution o f the pressure on curved sliding Figure 6. Active and passive earth pressure according to surfaces in his earth pressure computations. He presented the CULMANN (1866) (from: Kalle & Zentgraf, 1992). solution as an ordinary differential equation. In C OULOM B’S method, the direction o f the earth pressure is stipulated, so that

2078 the solution requires the determination o f a scalar. By contrast, o f experimental research that also considered dimensional effects KÖ TTER’s procedure does not assume the direction o f the earth and led to a theory o f models. PRANDTL applied his theory o f pressure, so that a vector has to be determined (Dietrich, 1985). the flow o f plastic materials also to soil and developed simple A s a professor for structural analysis at the Technical Univer­ equations for the major components of ground deform ation. sity of Berlin (Technische Hochschule Berlin), HEIN RICH From his research on pencils o f rays consisting o f straight lines FRANZ BERNHARD MÜLLER-BRESLAU (1851-1925) car­ and spirals as possible slip surfaces in earth pressure theory, he ried out tests in an earth pressure box he had developed, which, developed the method o f foundation failure analysis named after for that time, was exemplarily well-equipped with measuring him. This method, which allows to determine the bearing capac­ devices. Figure 8 shows the larger follow-up model o f this earth ity o f the ground subject to loading from a foundation, is de­ pressure apparatus, which was also planned by MÜLLER­ scribed in his publication of 1920, whereas he had established BRESLA U and in which systematic earth pressure tests were the fundamentals o f his approach already about 15 years earlier carried out for the first time (W eiss, 1978). (Dietrich, 1985). PRANDTL included first co­ efficients in his publication.

1 Elastic Area 2 Radial Slip Area 3 Passive Rankine Condition

Figure 9. Foundation failure according to PRANDTL (1920) (from: Terzaghi, 1954).

THEODOR VON KARMAN (1881-1963), who was bom in the Hungarian capital o f Budapest and worked, among other things, as an assistant to PRANDTL before he became professo r at Aachen Technical University (RW TH), investigated the maxi­ mum strength o f sandstone for increasing values o f the interme­ diate principal stress. In his publication o f 1926 on elastic limit states, he concluded that for an exact determinatio n o f the stress field, precise knowledge about the load history is necessary. W ith respect to a further development o f earth pressure theory, it was KA RMA N’s objective to find a stress field in the sense of KO TTER that results in a sliding surface along the rear o f a re­ taining wall (Dietrich, 1985).

2.4 Slope Failure

HANS DETLEF KREY (1866-1928), who was, among other things, assistant to M ÜLLER-BRESLA U in Berlin and later be­ came a professor himself, published on earth pressure theory and on the foundation failure failure o f retaining walls. For the latter, he developed a new formulation o f the slice method, which he presented among other things in his publication o f 1926 (Krey, Figure 8. Earth pressure apparatus by M ÜLLER-BRESLA U 1926). (1933) (from: Muhs, 1985).

His contribution to the theory o f earth pressure co nsisted in the extension of COULOM B’S theory by an inclination of the re­ taining wall and the ground surface, and thus by an inclination o f the resulting earth pressure. The analytical method s used today to determine the earth pressure are based on the trigonometric formulae derived by MÜLLER-BRESLAU (1906). Finally, HANS REISSN ER (1874-1967) from Berlin shall be mentioned, who compared COULOMB’S and KÖTTER’s solutions to the earth pressure problem (Dietrich, 1985).

2.3 Foundation Failure

Apart from his research mentioned above on the flow behaviour of fluids with small inner friction, LUDWIG PRANDTL also Figure 10. Slice method according to KREY (1926) (from: worked on soil mechanics problems. This resulted in a new form Hedde, 1929).

2079 The slice method was originally developed by the Sw ede lished important treatises on theoretical mechanics and the the­ HULTIN in 1916. Later the Dane FELLEN1US (1926) carried ory o f elasticity. He was the first one to investig ate the plane on the development. In 1951, KA RL VON TERZAGHI (1883- strain and plane stress states and he offered solutions for a point 1963) supplemented the slice method by a possibility to consider load acting on the horizontal surface o f an elastic isotropic half­ excess pore water pressures. space. The theory by HERTZ is similar to that of Figure 11 shows an example o f a slope failure near the town BOUSSIN ESQ, but HERTZ described the pressure distribution o f Körle. This picture clearly shows the sliding surface on which in the contact area under a loaded sphere by means o f the poten­ the shear strength was exceeded. tial theory. He also found out that only elastic deformations oc­ cur if the load on the sphere does not exceed a certain limit (Foppl, 1920). A UGUST FOPPL, professor at the Technical University in Munich, worked among other things on the basis of H ERTZ ’ theories. He investigated the differences in behaviour between the elements on the surface and those in the centre o f a body and determined an influence function for the surface settlements o f an elastic isotropic halfspace subjected to a vertical load. Fur­ thermore, he developed the experimental method o f p hotoelas­ ticity. Other treatises on loadings on an elastic halfspace were pub­ lished by WIEGHARDT (1922) and SCHLEICHER (1926), amongst others. KOGLER and SCHE1DIG investigated experi­ mentally the behaviour o f rigid foundations in sand y soils, resp. fills. The results were published in 1927 and 1928 in various issues of the journal "Die Bautechnik" (civil engineering) (W eiss, 1978). EMIL WINKLER, who simultaneously with MOHR intro­ duced the term "influence lines" and their application into struc­ tural analysis, explained in a publication o f 1867 the basis o f the modulus o f subgrade reaction method used often today to calcu­ late the moments and cross forces in a flexible foundation on a Figure 11. Slope failure near Körle. deformable subsoil (Winkler, 1867). The elastic mod el o f the In this context, the procedure that EGIDIUS KRA NZ presented subsoil formulated for the first time by W IN KLER co nsists o f a in his publication o f 1940 for the determination o f the necessary system of vertical, unrestrained, and independent springs anchor length for tied sheet pile walls has to be m entioned as (W IN KLER’s halfspace). W INKLER assumes that the contact well. The "stability analysis for the deep sliding surface", often pressure at the bottom o f a loaded, elastic and prismatic beam is performed in Germany, is to prevent sliding o f a so il mass com­ proportional to the settlement at the same point. Today the pro­ pletely including the anchors on a sliding surface running portionality factor is called modulus of subgrade reaction through the anchor ends. It thus verifies that the retaining anchor (Grasshoff & Kany, 1992). forces can be effectively transferred into the subsoil.

p [kN/ m2]

Figure 13. Modulus of subgrade reaction according to W INKLER (1867) (from: G rasshoff* Kany, 1992).

Figure 12. Stability analysis for the deep sliding surface accord­ In summary, it can be stated that these achievements enabled a ing to KRA NZ (1940). good description o f the mechanical behaviour o f soils and, with the fundamentals mentioned above, the seepage flow. However, it was not yet possible to capture the interaction o f solids and Since grouted anchors were developed only later (see chapter 5), water. With some exceptions, the testing technique imperative sheet pile walls were tied back with anchor walls o r anchor for soil mechanics research was very underdeveloped as well. slabs. In the context o f the failure analysis for the anchorage soil, Furthermore, in the author's opinion the expositions above verify which has to be performed for such structures, BUCH HOLZ the assessment made at the beginning o f this paper, that the sci­ (1931) calculated the critical anchor spacing, depending on the entific developments in the Central European countries are diffi­ bedding of the anchor slabs, for which the full passive earth cult to regard separate from each other. pressure o f a continuous anchor wall can be assumed.

3. SOIL MECHANICS AS AN ENGINEERING SCIENCE 2.5 Theory o f Elasticity The establishment o f soil mechanics as an independent engi­ The most important findings by previously mentioned neering science is closely related to the name o f TERZAGHI. BO USSIN ESQ in the area o f mechanics are not his contribution Before him, research in the field o f soil mechanics was mainly to earth pressure theory, but the mathematical solution for the done by scientists from the areas o f mathematics, technical me­ elastic halfspace subjected to a point load. The German physicist chanics, and hydraulics. HEINRICH RUDOLF HERTZ (1857-1894), who, among other KA RL VON TERZAGHI was bom as the son of an army of­ things, proved the existence o f electromagnetic wav es, also pub­ ficer in , now capital o f the . After com­

2080 pleting his studies o f and g eology at the Technical University o f , he worked on foundation projects in St. Petersburg in , among other things. It was there that he became aware o f the unsatisfactory state of know ledge in foundation engineering, and he started summarizing this state o f knowledge in a scientific treatise. After his docto rate at the Technical University o f Graz in 1912 and subsequent geological studies in the US, he became an officer on an air force test base in , where he worked together with THEOD OR VON KARMAN and RICHARD VON M ISES. As the organizer of engineering education in Turkey, FORCHHEIMER, TERZA GHI's supervisor in Graz, was instrumental in the ap­ pointment o f TERZA GHI to professor for foundation engineer­ ing in Constantinople (today: ) in 1916. During his ten years o f work in Istanbul, TERZA GHI developed soil mechanics into an independent discipline. He started first systematic tests with soil, in the beginning with sands. At the American in Istanbul, he founded a ground engineering laboratory and carried out first tests on consolidation. In 1923, he estab­ lished the differential equations describing the one-dimensional consolidation process, which are frequently used to day. In 1924, he presented his findings at the 1st International Conference on Applied Mechanics in Delft, Netherlands, and in 1925, he pub­ lished his well-known book "Erdbaumechanik auf bodenphysi­ kalischer Grundlage" (Earthwork mechanics based on soil phys­ ics) (Terzaghi, 1925). During the years 1925 to 1929, TERZAGHI continued the development of soil mechanics test devices at M .I.T. (Massachusetts Institute o f Technology). Thus, in 1926 he built a first (miniature) consolidation device. W hile at that time pile foundations were used in difficult subsoil condi­ tions when in doubt, TERZA GHI was the first who dared to use flat foundations even for larger buildings on clay. As o f 1930, he was professor at the Technical University o f (Technische Hochschule Wien) and, among other things, gave guest lectures Figure 14. Direct shear box by KREY (1926) (from: M uhs, at the Technical University o f Berlin (1935) and Harvard Uni­ 1985). versity (1936) (Casagrande, 1964). Another connection to Berlin was the German Research Society for Soil Mechanics, DEGEBO, o f which he was a member during the years 1930- to determine the peak strength as well as the residual strength in 1939. TERZAGHI’s close co-worker, ARTHUR shear zones o f soils (Muhs, 1985). CASAGRANDE, did research work there for years (Weiss, In 1927, his collaborator EHRENBERG developed the first 1978). triaxial apparatus, which was designed to make it p ossible to In 1936, TERZA GHI was elected first president o f the Inter­ investigate the strength and deformability o f a soil specimen national Society for Soil Mechanics and Foundation Engineer­ without the influence o f wall friction. In the beginning, this ap­ ing. Up to its 4th conference in 1957, TERZA GHI was president paratus was only intended to serve for the investig ation o f the o f the society. At this time, he had already moved permanently compression behaviour o f soils. Later, it was also used to deter­ to the US, where he was teaching as a professor at Harvard since mine the shear strength o f dam fill material o f clay and gravel 1946 (Casagrande, 1964). (Muhs, 1985). The new science, which, in the beginnings, was deno minated as "earthwork mechanics", tried, apart from frictio n and cohe­ sion, also to comprehend both qualitatively and quantitatively the other parameters determining the soil properties, such as, for example, grain-size distribution, plasticity, water content, and the influence o f time on the mechanical behaviour. One o f the major tasks, as seen by TERZA GHI, consisted in the mathemati­ cal description o f time-dependent clay layer settlements, which was made possible by his partial differential equations for the one-dimensional consolidation theory. The strong influence TERZAGHI had also on German re­ search in soil mechanics and foundation engineering can only be assessed in connection with the research institutes that existed at that time. In 1799, the Technical University of Berlin was founded, where M ÜLLER-BRESLA U as professor for structural analysis carried out his above mentioned investigations with the earth pressure apparatus. After Berlin, technical academies or universities were founded in other German cities as well during the beginning o f the 19th century: Karlsruhe (1825), Dresden (1828), Stuttgart (1829), and (1831). The Imperial Re­ search Institution for Hydraulic Engineering and Shipbuilding, founded in Berlin in 1903, can be considered as the first geo- technical research institute in Germany. In this institute, renamed 1 Air 2 Glass Cylinder in 1919 into Prussian Research Institution for Hydraulic Engi­ 3 Rubber Skin neering and Shipbuilding, mainly research work on earth pres­ sure was done in the first years under the directio n o f KREY. In Figure 15. Triaxial apparatus according to EH REN BER G (1927) 1926, KREY developed the first shear box that made it possible (from: Muhs, 1985).

2081 KREY and TIEDEMANN, the latter o f whom developed a ring BRESLA U as professor for structural analysis at the Technical shear apparatus in 1937, were the first to prove by shear tests University o f Berlin, was to be regarded as the strongest sup­ that the cohesion o f a soil depends on its load history. JOHANN porter o f the linkage o f the DEGEBO to the Technical Univer­ OHDE (1905-1953) succeeded in his time as an employ ee o f the sity o f Berlin. The research programme o f the DEGEBO was Prussian Research Institution in developing a metho d for the very diverse and consisted among other things o f research into determination o f the wall pressure distribution for various types the deep action o f compaction devices and into the settlement o f wall movement assuming curved sliding surfaces. He later behaviour o f sands under dynamic loading. Resulting from re­ became the director o f foundation engineering o f the Research search on compaction by vibration, for example, the method to Institution for Shipping and Hydraulic and Foundation Engi­ determine the minimum and maximum densities o f non-cohesive neering, w hich had come from the Prussian Research Institution, soils, which is still in use today in subsoil investigations, was and professor at the Technical University o f Dresden (Techni- developed. In 1932, the first vibrator was used for soil dynamics sche Hochschule Dresden). Among other things, OHDE also tests. Among the newly developed test devices there is also an worked on the determination o f the contact pressure distribution apparatus corresponding in principle to a vane shear device. A Under shallow foundations. We owe him the formulation o f the patent on this device was applied for in 1929. The further devel­ well-known constrained modulus method. opment o f this test device, which allows the determ ination o f the In 1914, FRA NZIUS, professor for foundation and hyd raulic shear strength in situ, later was brought about outside of Ger­ engineering in Hanover, established a foundation engineering many (Schultze & Muhs, 1967). laboratory, which mainly served the investigation o f soil me­ Extensive research was carried out to determine the behaviour chanics problems connected to hydraulic engineering . After the o f the sands in place in Berlin. In a mushroom-shaped caisson, foundation o f the Hanover Institute for Foundation and Hydrau­ especially built for these investigations, plate bearing tests were lic Engineering under the direction of FRANZIUS in 1927, carried out to determine the shape coefficients necessary for STRECK taught as o f 1932 in Hanover as the first outside lec­ foundation failure analyses. In cooperation with the KELLER turer for soil mechanics (Rizkallah, 1985). and FRA NKI companies, tests concerning deep vibrato ry com­ KOGLER, the director o f the earthwork laboratory that had paction resp. the compaction o f gravel piles, predecessors to the been founded in 1924 at the Freiberg Research Institution, de­ modem FRANKI pile, were carried out. These methods will be veloped in 1933 the first lateral pressure apparatus for the hori­ described in more detail below. Finally, in this co ntext the de­ zontal loading o f a borehole wall. It largely resem bles the now velopment o f the DEGEBO static penetrometer o f 1944 shall be well-known pressiometer by MENARD (Schultze & Muhs, mentioned, which, contrary to the already existing Dutch cone 1967). device, was designed as a one-rod penetrometer. A strain gauge Co-workers at the Freiberg Research Institution were, amongst is built into the point o f this penetrometer to measure the point others, LEUSSIN K and SCHEIDIG. The latter was a disciple of load. By measuring the applied load, the portion o f load resulting TERZA GHI and carried out tests concerning the pressure distri­ from skin friction can be derived (W eiss, 1978). bution under bearing plates on sand fills. After KO GLER's In the penetrometers after the Dutch measuring principle, the death, the Freiberg Earthwork Laboratory was incorporated into sounding rod and the jacket moved separately. This held the the Technical University o f Dresden in 1939. BERNA TZ IK, an danger o f soil particles becoming stuck in the apparatus resp. Austrian and disciple o f TERZA GHI, became its director. Al­ inaccuracies developing due to friction betw een the sounding rod ready since 1936, the Technical University o f Dresd en possessed and the jacket (Schultze & Muhs, 1967). a laboratory for earthwork and foundation mechanics investiga­ tions under the direction o f N EUFFER. The German Research Society for Soil Mechanics (DEG EBO) shall be mentioned here in particular. It consisted o f members from science, construction administration and construction in­ dustry and was a unit o f the Technical University o f Berlin, al­ though largely independent. Amongst the initially o nly 27 mem­ bers o f the D EGEBO , which, like similar institutions in the USA and Sweden, was intended as an agency for subsoil problems experience, were well-known scientists such as TERZ AGHI, FRANZIUS, KOGLER, AGATZ, HERTWIG, DIENEMANN, LOOS and BUSCH, to name but a few (Weiss, 1978). On the grounds o f his strong interest in research into the influence of vibrations in the subsoil, HERTW IG, successor to MU LLER-

1 Pressure Gauge

2 Compressed Air

3 Gas Gauge

4 Casing

5 Rubber Membrane

Figure 16. Lateral pressure apparatus according to KOGLER (1933) (from: Schultze & Muhs, 1967). Figure 17. Sounding with the DEGEBO static penetrom eter (from: Schultze & Muhs, 1967).

2082 Spihendrudt 1S0 m'ghm'iso 200 1 Clay with Sand 1 Ton m it Sand- Inclusions

2 Organic Deposit ooganische

3 Fine and Medium Sand Soil Sample 4 Pile Base Plane 0100 mm 3 h = 40 mm Fein-und 5 Depth [m] M ittdsand 6,0 Filter Stones 6 Point Resistance [kg/cm2] Rubber Ring

Load

Gauge

Steel Ball

Figure 18. Results o f a static penetration test (from: Schultze & Figure 20. Compression-permeability device by Muhs, 1967). A. CA SA GRA NDE (vertical section) (from: Weiss, 1978).

As o f 1933, the further development o f laboratory testing tech­ In order to coordinate the practical work o f the above mentioned nique was carried out with the assistance o f LEO and ARTHUR soil mechanics research institutes, the German Comm ittee for CASAGRANDE, the latter of whom had formerly worked for Ground Research was founded in 1927 within the Germ an Soci­ TERZAGHI in Vienna. The purchase o f the following, newly ety for Civil Engineering. Its members from science and practice developed test devices should be highlighted: compression- represented the specific research in the field o f geotechnical en­ permeability device (see figure 19), direct shear apparatus and gineering and produced technical regulations to be applied in liquid limit device. In addition, as o f 1935, RENDU LIC contin­ geotechnical practice. Apart from the development o f suitability ued at DEGEBO his experimental work on the measurem ent of and strength tests, several guidelines were published. In addition pore water pressures in soil samples, which he had started when to the guidelines "Soil sampling and the treatment of soil sam­ he was working for TERZA GHI in Vienna (W eiss, 1978). ples" (1928), "Test loadings" (1929), and "Designation of soil types, stratigraphic table" (1929), there are also the "Guidelines for Soil Investigations in Civil Engineering" (1935), the 2nd edi­ tion o f which, issued in 1937, was re-issued 60 years later as a reprint. A hardcover copy o f it was presented to each participant of the XlVth International Conference on Soil Mechanics and Foundation Engineering in Hamburg.

4. THE "BEGINNINGS" OF FOUNDATION ENGINEERING

With progressing technology in Germany and Europe in the 19th and 20th century, the civil engineering tasks grew as well. Par­ ticularly to solve the transportation problems that had arisen from the increasing industrialization and the resulting centraliza­ tion o f the w orkplaces, new technologies in the field of founda­ tion engineering had to be developed. Especially in railway con­ struction, later also in road and subway construction, new meth­ ods for more economical and safe construction were applied. In this context, the demands were also increasing on geotechnical engineering, which is to provide the tools for the engineer to describe and determine the mechanical behaviour of soils re­ spectively rock for the planned construction as well as possible. Apart from the tasks in the field o f transportation construction, which also includes canal and harbour construction, the tasks in the area o f energy and water supply, such as dam co nstruction, should be mentioned here. In the follow ing, some examples from the development o f foundation engineering in Germany in the 19th and 20th century are presented. In 1822, PHILIPP HOLZMANN Co. employed for the first time a wooden diving bell for the sinking o f the fo undations o f a bridge over the river Limmat in Zurich, Switzerland (Krabbe, Figure 19. Compression-permeability device by 1985). A. CASAGRANDE (from: Weiss, 1978).

2083 Figure 23. Construction o f timber sheeting betw een driven gird­ Figure 21. Bridge over the river Limmat in Zurich, Sw itzerland ers (1900) (from: Kress, 1922). (1822) (from: Krabbe, 1985).

Figure 22. Compressed air shield for the Spree tunnel in Berlin (1895) (from: Krabbe, 1985).

As early as 1877, PHILIPP HOLZMANN Co. sank the pillars for the Wettstein bridge over the river Rhine near Basle, Swit­ zerland, by means o f compressed air. The iron caissons used for this purpose were suspended from a wooden frame. The com­ pressed air was at that time produced by steam engines. For the construction o f a subway tunnel underneath the river Spree in Berlin, PHILIPP HOLZMANN Co. used a compressed air shield already in 1895 (Krabbe, 1985). Between 1907 and 1911, a compressed air shield was also ap­ plied by PHILIPP HOLZMANN Co. for the construction o f the first tunnel in Hamburg (Krabbe, 1985). In order to support excavations for cut-and-cover tunnels, wooden sheet pile w alls were frequently used. In 1900, in Berlin for the first time single iron girders were driven spaced at 1.5 m to avoid vibrations caused by sheet pile driving. A fter excavation Figure 24. Construction pit for the trade fair tower in Frankfurt of a sloped construction pit down to the ground water table, on the Main (from: Bauer, 1997) which at this place was located approx. 3 m underneath the ground surface, the girders were driven. Subsequently, after ground water lowering, horizontal timber sheeting w as inserted tions were developed in other German cities as well during the in between these piles in the course o f the construction pit exca­ construction o f underground transportation systems. Examples vation. It became necessary to decrease the vibrations because in are the "Essen supporting system" and the "Hamburg supporting the track section depicted in figure 23 the subway ran at a dis­ system". tance o f only 4 m to the Emperor Wilhelm Memorial Church, to The HOESCH sheet piles go back to an invention by be seen in the background (Kress, 1922). TRYGGVE LARSSEN, state engineer in Bremen, in 1902. This method was substantially improved in 1908 by p ulling and While in the beginning mainly used in hydraulic engineering, thus reclaiming the iron girders after the completion o f the tun­ nowadays sheet piles are used in many areas of specialized nel. This type o f retaining structure, which later became known heavy construction. as the "Berlin supporting system", was frequently used outside o f The development o f building construction in Germany at the Germany as well for the construction o f cut-and-cov er tunnels. beginning o f the 20th century, especially with respect to the Nowadays, horizontal timber sheeting is used mainly for con­ large buildings planned in Berlin, involved higher subsoil loads. struction pit support. Especially for shallow construction pits, In order to improve the density of sands and gravel even at resp. for the shallow portion o f deep construction pits, this type greater depth, where traditional compaction devices failed, first o f building pit support is recommendable for reasons o f flexibil­ techniques were developed by JOHANN KELLER and ity and economy. FRA N KI. In order to assess and quantify the increase in bearing It is yet to be mentioned in this context, that in later years special capacity o f the subsoil, comprehensive field tests were carried support techniques and adaptations to the local subsoil condi- out in Berlin in 1939 with the two techniques in co operation with

2084 the German Research Society for Soil Mechanics (DEG EBO) The technique for the installation o f such sand and gravel piles (W eiss, 1978). had already been applied during the construction o f the Nurem­ In deep tamping, the technique developed by FRA NKI Co., a berg congress hall in 1936. The FRANKI pile more co mmonly mixture o f sand and gravel is tamped out o f a casing driven ver­ known today differs insofar from this technique as, instead o f a tically into the ground. Aside from the bearing capacity o f the mixture o f sand and gravel, concrete with connecting rebars in soil column, the bearing capacity o f the surrounding soil is also the upper part is used. The use o f the FRA NKI pile is reported improved due to the displacement and compaction. Figure 25 already for the construction o f the Dortmund-Ems canal aque­ depicts the principle o f deep tamping according to FRANKI Co. duct over the rivers Lippe and Stever in 1934 (Stecher, 1934), Figure 26 shows the compaction tests in Berlin in 1939 (W eiss, among other things. 1978). Another technique for soil improvement that was also devel­ oped at that time is the deep vibratory compaction technique by KELLER Co. o f Frankfurt. As early as 1933, KELLER Co. held the first patent for a depth vibrator. Figure 27 depicts such a depth vibrator o f the first generation during a test-run on the premises o f KELLER Co. (Kirsch, 1985). The first contract on the application o f the so-called vibro com­ paction, also within the framework o f the construction o f the congress hall in Nuremberg, was signed in 1936. The technical results were encouraging, but the technique in itself was too un­ economic since compaction at greater depths required cased boreholes. Further endeavours focused on developing a device strong enough to reach the necessary depth by its o wn vibrations. The first vibrator that was able to achieve this and that already possessed the characteristics o f a modem device as, for example, the upper and lower water discharge openings, was commis­ sioned in 1937 (Kirsch, 1985). The sequence o f operations dur­ ing vibro compaction by KELLER Co. is shown in principle in figure 28. During the tests mentioned above performed in cooperation w ith. DEGEBO in 1939, it was possible to compact the subsoil up to a maximum depth o f 35 m. It was not until 40 years later that the same depth was reached during compaction works for the Jebba dam in Nigeria (Kirsch, 1985).

4 Plug Enlargement by Tamping 5 Addition of Gravel Sand 6 Final State

Figure 25. Principle o f deep tamping according to FRANKI Co. (from: W eiss, 1978)

Figure 26. Compaction tests at DEGEBO (1939) (from: Weiss, Figure 27. Depth vibrator o f the first generation by KELLER Co. 1978) (1933-1937) (from: Kirsch, 1985).

2085 The history o f the grouting technique, another possibility o f is cooled until the pore water freezes. As compared to the non­ soil improvement, begins in 1802. In that year, the Frenchman frozen condition, the soil obtains a greater strength and, at the CHA RLES BERIGN Y undertook the first grouting works with a same time, becomes impermeable (Jessberger, 1996). This tech­ suspension o f water and cement. The term "injection technique" nique was first applied during the years 1898 to 1903 when 26 (procédé d’injection) also goes back to him. The first known shafts were sunk by means of ground freezing. In civil engi­ applications o f this technique in Germany were in m ining and neering, especially in tunnelling, this technique has only been tunnel construction in the second half o f the 19th century, for applied more often since the end o f the sixties. example at the Rheinpreussen I mine (1864) and the Forst tunnel Since energy has to be constantly supplied in order to main­ o f the Black Forest Railw ay line (1872) (Kutzner, 1991). tain the frozen body, artificial ground freezing is predominantly Up to the beginning o f the 20th century, developments in the to be regarded as an auxiliary construction measure (Jessberger, grouting technique consisted mainly o f improvements in the ce­ 1996). The advantages o f this technique are mainly that the ments as well as the machinery and devices. An impo rtant prog­ ground water table is only influenced to a small degree, and that ress was achieved in 1926 with the invention o f chemical grout­ the natural condition and quality o f the water and the soil remain ing made in Germany by the Dutchman JOOSTEN . In that year, unchanged. However, a prerequisite for the application o f this JOO STEN received a German patent for his technique. (Kutzner, procedure is the existence o f a sufficient amount o f water in the 1991). Although already before JOOSTEN French engineers and soil layers to be frozen. others had already performed chemical grouting, up to 1950 the The ground freezing technique is still widely used today and JOOSTEN technique was the only fully developed and practi­ since it is an environmentally friendly technique, it becomes cally applicable chemical grouting technique. increasingly interesting. An example for a recent application in The JOOSTEN technique is based on the formation o f a silica shaft construction are the freezing shafts for the exploration o f gel from water glass and calcium chloride. The two materials are the Gorleben salt dome. An example for ground freezing in tun­ injected into the ground one after the other (Kutzner, 1991). nelling is the Stuttgart rapid transportation system. During con­ There is a sudden reaction o f the two materials. The range o f the struction o f contract section 12, the subsoil was frozen via hori­ grain size distribution of soils suitable for grouting by the zontal advancing boreholes above the tunnel roof. Calcium chlo­ JO O STEN technique is depicted in figure 29. ride brine was conducted through up to 40-m-long steel pipes at During the year o f his patent application, JOOSTEN himself up to -40 °C, cooling down the surrounding ground and the began a large-scale test in Nordhausen. In order to investigate groundwater to approx. -5° C. Test this. The iced shield thus the durability o f the compaction material, a shaft was sunk in a created was more than one meter thick and had an op ening angle previously fabricated injection body. The walls o f the shaft are o f approx. 120° (Griiter & Liening, 1976; W ittke & Rifller, 1976; still standing unsupported today. After 1930, the JOOSTEN Jonuscheit, 1976). The figures given below show a longitudinal technique was applied for example to a large degree during the section as well as two typical cross sections o f the tunnel (figure construction o f the underground transportation system in Berlin, 30) as well as a view on the tunnel face (figure 31). among other things for the underpinning o f the Stettin Station in 1935 (Kutzner, 1991). In 1883, the German FRIEDRICH HERRMANN POETSCH published a patent specification in which he described his inven­ tion, the standard technique still in use today for shaft sinking by ground freezing (Arz et al., 1991). In this technique, the ground

Grain diam eter [mm ] Figure 29. Range of application of the JOOSTEN technique (1926).

1 Sluicing 2 Compaction 3 Water Discharge

4 Addition of Soil 5 Final State

Figure 28. Sequence o f operations during vibro comp action by Figure 30. Stuttgart rapid transportation system, contract sec­ KELLER Co. (from: W eiss, 1978). tion 12 (advancing ground freezing).

2086 - up to 17 more members o f the board.

The follow ing representatives o f other associations also belong to the board o f directors:

- the president of the Federation o f the German Construction Industry (Hauptverband der Deutschen Bauindustrie, HVBI)

the president o f the German Institute o f Structural Engineer­ ing (Deutsches Institut fur Bautechnik, DIBt)

- the chairman o f the German Geological Society (Deutsche Geologische Gesellschaft, DGG)

the chairman o f the Society for Harbour Engineering (Ha­ fenbautechnische Gesellschaft, HTG)

- a board member of the German Association for Water Re­ sources and Land Improvement (Deutscher Verband fur Was­ serwirtschaft und Kulturbau, DVW K)

- the president o f the Federal Institute for Earth Sciences and Raw Materials (Bundesanstalt für Geowissenschaften und Rohstoffe, BGR). Figure 31. Stuttgart rapid transportation system, contract sec­ tion 12 (heading under ground freezing support). Among other things, this assures the cooperation o f all institu­ tions interested in geotechnical engineering. For the enhancement o f professional exchange in the individ­ 5. DEVELOPMENT AFTER 1950 ual branches, the following 6 special chapters were formed within the DGGT : In 1948, the German Committee for Ground Research w as re­ activated. At first, it was active within the framework o f the Soil Mechanics German Committee on Standards as "Working Group Gro und". It soon, how ever became apparent that many geotechnical ques­ - Rock Mechanics tions extended beyond thi framework o f the German Committee on Standards and that there was a particular need for the scien­ Engineering tific results to be imparted in a practice-oriented way beyond the framework o f standards. Therefore, at the National Conference Earthw orks and Foundation Engineering for Earthw ork and Foundation Engineering in Karlsruhe in 1950, the German Society for Soil Mechanics and Foundatio n Engi­ Geosynthetics neering (Deutsche Gesellschaft fur Erd- und Grundbau (DGEG)) was founded, which deals with all geotechnical tasks beyond Landfills and Contaminated Land. standardization. ERICH LOHMEYER was elected the first president o f the society (Smoltczyk, 1992). The most important national event o f the DGGT is the biennial The tasks o f this society, which was renamed in 1994 into Ground Conference, which attracts approx. 1500 participants. German Geotechnical Society (Deutsche Gesellschaft fur Geo- Apart from this conference, there are several sympo sia of the technik (D GGT)), are summarized in its statutes as follow s: special chapters rock mechanics, engineering geolog y, geosyn­ thetics and landfills and contaminated land, which are each at­ a) the scientific research into ground, soil, and rock, and their tended by approx. 300 - 500 persons. behaviour under all types o f loading; b) the improvement o f analysis and design o f structures in soil The tasks o f the society are dealt with primarily in working and rock as well as building foundations with the o bjective groups, which are constituted for a limited period from among o f safe, economic and environmentally friendly construction; the members o f the society. At present, there are approx. 40 working groups elaborating technical recommendations and c) the elaboration and publication o f directives, guidelines and guidelines. On the XlVth International Conference on Soil Me­ other publications for the analysis and design o f structures chanics and Foundation Engineering in Hamburg, the Technical and construction practice, which are to make the results re­ Recommendations "GLC" on Geotechnics of Landfills and lating to a) and b) available in an easy-to-comprehend style Contaminated Land were published. Apart from the recommen­ (DGGT, 1994). dations, published at irregular intervals, the quarterly "Geotech­ nik" and the annual "Pocket Book for Tunnelling" are edited by In 1997, the German Geotechnical Society (DGGT) has approx. the DGGT. 1800 members, which comprises ordinary and extraord inary Finally, it should be mentioned that the DGGT is associated members, sponsors, and students. The board of the D GGT is with the follow ing international professional organizations: made up o f representatives from all institutions and professions who are involved in geotechnical projects, such as the construc­ - International Society for Soil Mechanics and Foundation En­ tion industry, public authorities, clients, universities, and con­ gineering (ISSM FE) sulting engineers. More specific, the board o f the DGGT consists o f - International Society for Rock Mechanics (ISRM )

- the chairman - International Society for Engineering Geology (IA EG)

- the vice-chairman International Geosynthetics Society (IGS).

- the chairmen o f the special chapters

2087 Two of its representatives (LANGER (IAEG) and WITTK E (ISRM )) have been international presidents. 2a i k/Dh k j [m/s] =k, (Soil) The work performed by the German Geotechnical Society would not be possible without the results obtained in geotechni­ g 0,0 32 0,6 • 10 -° cal theory and practice by various public and private institutions. o.im m y/r/ ys/// ?)' Silt The following list is intended as a brief compilation o f the pres­ 0,25 0,3 ■ 10 * ent main research topics in the field o f geotechnical engineering ...... '¿¿2ZW //TÆ g 0,032 0,5 • 10 -® at the German universities. Although the different foci listed 0,2mm v/////////} 0,25 0,2 • 10 ^ below have developed in research and academic education with î the progress o f the activities, it must be emphasized that the re­ g 0,032 0 ,4 - 10 -* 0.4mm spective areas cannot be sharply delimited. In addition, other Sand //////7S/7/, 0,25 0,2 • 10 ■* topics that are not listed here have been dealt with at the respec­ tive geotechnical institutes. Besides, the achievem ents of com­ < 0,032 0,2 • 10 ^ paratively young academic institutions, such as, fo r example, ° ’7mm '//////SÍ7Á comprehensive universities, or o f non-university research insti­ 0,25 0,1 -I O -3 tutes, like the Federal Institute for Hydraulic Engineering (Bun­ desanstalt für Wasserbau), the Bavarian State Commercial In­ stitute (Landesgew erbeanstalt Bayern) or the Federal Institute for 'S/////////Z' g 0,032 0,6 ■ 10 ^ Càravel Road Construction (Bundesanstalt fiir Straßenbau), should be 1,0mm emphasized. V////////Â 0,25 0,3 • 10 -3

Aachen: rock mechanics, tunnelling, numerical metho ds, environmental geotechnics Figure 32. Permeability o f jointed rock (joint spacing: lm).

Berlin: soil dynamics

Bochum: environmental geotechnics, centrifuge model testing

Brunsw ick: piles, monitoring, environmental geotechnics

- Darmstadt: foundations, soil mechanics o f tertiary clay

Dresden: earth pressure, foundations

Freiberg: liquefaction o f soils, rock mechanics

Hanover: slurry trench walls, coastal engineering

- Karlsruhe: theoretical soil mechanics, rock mechanics

- Munich: geosynthetics, compaction

Stuttgart: constitutive laws, numerical methods

In the following, developments that had their beginnings in Germany shall be highlighted. In the area o f rock m echanics and rock engineering, the three-dimensional stability analysis o f spa­ tial rock wedges has to be mentioned, where the dev elopment o f the procedures occurred at the same time but independently o f each other in France and Germany. The stability o f a rock wedge bedded on multiple planes can be determined graphically, by means o f a nomogram or analytically (Wittke, 1965, 1984). An­ other calculation method for the stability analysis of three- dimensional rock wedges was introduced by the Frenchman LONDE (1965). For the establishment o f the flow and resistance laws describ­ ing the seepage flow behaviour of open joints with non­ contacting w alls, extensive laboratory tests were carried out by, Figure 33. Soil nailing (from: Bauer, 1997). amongst others, W ITTKE & LOUIS (1968) in Karlsruhe. By means o f these flow and resistance laws, permeability coeffi­ cients kT can be determined depending on the flow state and the In soil nailing, the soil itself is used to support a slope. By relative roughness k/ Dh o f a joint. means o f soil nails, w hich are placed in a nearly horizontal con­ Closely tied to rock mechanics is also the name o f LEOPOLD figuration favourable to the direction o f the maxim um principal MÜLLER (1908-1988), who was bom in Salzburg, . In strain o f a slope, the shear strength and shear stiffness o f the soil 1965, he was appointed to the rock mechanics chair o f the Tech­ is (anisotropically) increased (Gassier, 1987). nical University of Karlsruhe (Technische Hochschule In the fields o f boring technique and pile foundations, Ger­ Karlsruhe). In 1966, he became the first president o f the newly many looks back on many years o f experience as well. From the founded International Society for Rock Mechanics. large variety o f piles and pile manufacturing techniques in Ger­ The idea o f in situ soil stabilization by means o f iron rods was many, only a few examples can be named here. picked up in Germany in 1975. During 1976 - 1980, BAUER For deep drillings resp. bored piles in less stable ground, a Co. and the Institute for Soil Mechanics and Rock M echanics of mechanical borehole support in the form o f steel tubes is usually the Technical University o f Karlsruhe jointly investigated the applied. The tubes are installed by rotating and fo rcing individ­ innovative method o f soil nailing from the soil mechanics per­ ual pipe segments into the ground. Rotating back and forth re­ spective and developed this construction technique to practical duces the friction between the pipe casing and the ground. A applicability (Gassier, 1987). Figure 33 shows a nailed soil body, device especially designed for this procedure is the whose behaviour under high loading was investigated by a great HOCHSTRA SSER-W EISE pipe revolving machine (figure 34 number o f measuring instruments (Bauer, 1997). shows a model by BILFIN GER + BERGER Co.) (Ulrich, 1982).

2088 1 HW Swivel Arm 2 Clamshell Bucket Figure 35a. Post-grouted bored pile (from: Bauer, 1997). 3 Gravel Pump 4 Chisel 5 Concrete Placement Tube 6 Cover to pull out Tube with Compressed Air

Figure 34. HOCHSTRA SSER-W EISE pipe revolving machine (from: Ulrich, 1982).

An essential part o f this machine is the pneumatic HW swivel joist. At the ends o f the swivel joist, weights are mounted that rotate around the pipe axis until they hit a stop, thus revolving the pipe a little. This diminishes the skin frictio n while the tube is forced into the ground by its dead weight. The p ull-out o f the tubes is supported by compressed air. For the manufacturing o f bored piles, more recently very large and powerful machines Figure 35b. Load-settlement curves (from: Bauer, 1997). have been used. Besides performing the actual boring procedure, these machines can also force the casing necessary for borehole support into the ground, as well as pull out the tubes again dur­ ing concreting, by means o f their hydraulic pumps. In order to increase the bearing capacity o f cast-in-place con­ crete piles, as early as 1970, BA UER Co. started to develop a technique for the post-grouting o f piles. By means o f annular grouting, the soil is compacted in the area o f the shaft and an intensive interlocking between the pile concrete and the soil is obtained. In this way, it is possible to increase the skin friction and thus the bearing capacity o f the pile. During the additional pile base grouting, the contact zone between the pile base and the ground is grouted with a cement suspension. The injection pipes for post-grouting are fixed to the reinforcing cage. Since the grouting takes place before the final hardening, the pile con­ crete is broken up again. This way, some o f the loo sening o f the ground stemming from the pile manufacture is reversed. Figure 35a shows a post-grouted test pile with a diameter o f 570 mm, w hich after manufacture was excavated for inspection. In figure 35b, the load-settlement curves o f an ordinary and a base grouted bored pile are shown for comparison. Figure 35c shows the foundation o f the Misurata steel mill in Libya, where bored piles grouted annularly and at their base with diameters o f 450 mm and 600 mm were manufactured. Figure 35c. Foundation o f the M isurata steel mill (from: The disadvantage o f bored piles is the loosening o f the ground Bauer, 1997). during drilling, even if a casing is used. This resulted in the de­ velopment o f other cast-in-place concrete pile types. One of these is the continuous flight auger pile (SOB pile). This pile steel rod) into a borehole. The borehole is subsequently filled with a diameter o f 0.3 m to 1 m is produced with a continuous with cement grout. The steel link is centred via spring elements. flight auger drill (Stocker, 1986; Franke, 1992). Figure 36 shows Furthermore, a double corrosion protection can be achieved by the principle o f the manufacturing o f an SO B pile. arranging an additional ribbed tube around the steel rod, into First, the soil auger is drilled into the ground until it reaches the w hich cement grout is injected at the plant. level o f the pile base. During extraction, concrete is injected The advantages o f this type o f pile lie in the small borehole through the hollow auger and subsequently the reinforcing cage diameter (rod diameter 32-50 mm) resulting in minim al demands is forced or vibrated into the concrete. on the drilling technique. Thus smaller drilling equipment can be A special type o f pile is the GEW I pile (DYW IDA G, 1997). It used, enabling the manufacturing of piles in alread y existing is the most slender o f the so-called miniature drill piles. The buildings. Furthermore, drilling in harder soil or rock strata can GEW I pile is produced by inserting a threaded steel rod (GEW I be effected more easily.

2089 In 1958, the first injection anchors in soil were used for the construction o f the Bavarian Broadcasting Corporation (Bayeri- scher Rundfunk) building in Munich. JELIN EK, professor at the Technical University o f Munich, designed the first clear con­ struction pit with a Benoto pile wall and smooth steel rods (St 80/ 105, diameter 20 mm) drilled into shafts. Ho wever, never or only rarely were the shafts hit in the process. Thereupon, KARLHEINZ BA UER, the head o f BA UER Co., contractor for this project, successfully tried to concrete steel rods in the gravel, thereby making up for the time lost previously. The load- bearing capacity o f these first anchors in soil, fo r which later a patent was applied for, amounted to 200 kN. In 1995, during the construction o f a new building next to the Bavarian Broadcasting Corporation building, these first anchors were excavated (see figure 38) (Bauer, 1996). It can clearly be seen how it was attempted to reach the shafts with the smooth steel rods. On the right-hand side o f the figure is one of the Figure 36. Manufacturing of a continuous flight auger pile grouted anchors manufactured afterwards. (from: Bauer, 1997). While in 1960 6000 m of anchors were manufactured in Ger­ many (Stocker, 1985), nowadays approx. 6000 km are manu­ factured world-wide per year. An interesting development in rock anchors was made during the remedial works on the Eder dam. Between 1908 and 1914, the Eder masonry dam was built o f greywacke quarry stone masonry. It was constructed as an arched gravity dam, with a height o f 47 m and a crest length o f 400 m. The masonry dam is founded on equal shares o f lower carboniferous slate and greywacke. The Eder reservo ir has a length of 27 km and a volume of 202 million m3 (Wittke & Schroder, 1994). Examinations o f the structure showed that the stability o f the total system had been negatively influenced by seep age paths at the dam base and resulting base pressures. On econo mic grounds and in the interest o f the protection o f nature and o f historic monuments (preservation o f the outward appearance o f the dam), Clutch Collar

GEWI-Bar Brücke

Cement Grout Ankerkopf Neuer Stahlbetön-Lastvertellungsbafken + 242,20 NN Rib Sheath mit Innengang

Figure 37. GEW I pile with double corrosion protection (from: DYW IDAG, 1997). 104 anchors 450 tons each

45 m

70

TosbecK n

Grauwacke bzw. Tonschiefer

7+177.00 NN

10 m

Figure 38. Grouted anchor in soil. Figure 39. Cross section o f the Eder masonry dam after remedial works (from: Schwarz, 1994)

2090 it was decided to anchor the masonry dam into the bedrock to increase the safety against overturning during storage. A total o f 104 approx. 70 m long permanent rock anchors, system SUSPA , each with a working load o f 4500 kN were installed in boreholes extending up to approx. 30 m below the dam base (see figure 39). The tension elements o f the anchors used consist o f 34 wire strands each with a tensile elastic limit o f 1570 M Pa and a tensile strength o f 1770 MPa. The diameter o f a strand equals 15.2 mm resulting in an effective cross sectional area o f 150 mm2. In the approx. 10-m-long load transfer section, the strands are embed­ ded in a ribbed cement grouted plastic pipe. In the free steel sec­ tion, each strand possesses a corrosion protection sheathing con­ sisting o f grease and a plastic mantle tube. The strand bundles are again embedded in a thick plastic pipe. The installation o f the approx. 70 m long anchors in large boreholes (diameter 273 mm) was done by means o f a special deflection construction and a mobile crane (see figure 40). The safe transmission o f the high anchor forces was verified on Figure 40. A nchor installation (from: Schw arz, 1994). test anchors with forces o f up to 12500 kN. Furthermore, the anchor heads are designed to enable regular checking of the an­ chor forces and, if needed, retensioning o f the anchors (Wittke & Schroder, 1994). An auxiliary measure in traffic tunnelling is the soil fracturing method by KELLER Co. (soilfrac) (Raabe & Esters, 1986). An example o f the use o f this method is the undercrossing o f a high shelves warehouse o f Tetra Pak Co. in the course o f the con­ struction o f the Limburg tunnel as part o f the new high-speed railway line Cologne-Rhine/ Main. The subsidence resulting from the underground tunnelling will be compensated by ground heaving injections according to the soilfrac technique. The in­ jections are carried out by means of up to 45 m long boreholes drilled in a fanlike fashion in a horizontal plane under the high shelves warehouse. Narrow walls are diaphragm walls o f low thickness made o f a cemented, hardening sealing mass. They can be used for tempo­ rary as well as permanent purposes at small hydraulic pressure differences. The depth usually ranges between 8 and 20 m, while Figure 41. Narrow wall wing vibrator by KELLER Co. (from: the wall thickness depends largely on the subsoil. Keller, 1993) A narrow wall can be built by the vibration method, using a depth vibrator well-known from ground compaction. To this end, the depth vibrator is equipped with two diametrically mounted fins. During the sinking procedure a cavity is created that is filled with the narrow wall mass when the depth vibrato r is pulled back (Stocker & Walz, 1992). Figure 41 shows such a modified depth vibrator by KELLER Co. To enhance the Rhine flood protection dyke between the towns o f Engers and Neuwied, in 1984/ 85 a vibro membrane was built according to the KELLER technique with a length o f 1100 m and a depth o f up to 15 m. From a trench filled with sealing sus­ pension, the narrow wall wing vibrator was sunk using vibration, force and pressure sluicing. The developing trench and the adja­ cent pores immediately filled with the permanently elastic mass (Keller, 1993). On figure 42, the crawler-carrier w ith the wing vibrator is depicted in operation. In the following, some current major construction p rojects in Germany shall be presented. The enhancement o f the east-w est transportation links, which had been neglected resp. interrupted before the , has to be especially highlighted in this context. These very important east-w est axes are depicted in figure 43. Ten projects concern the environmentally friendly Figure 42. Vibro membrane System KELLER (from: Keller, transportation systems railways (nine) and inland w aterw ays 1993). (one); seven are road construction projects (Bundesministerium furVerkehr, 1992). For the enhancement o f the inland waterways network, the con­ the east o f Germany is first and foremost necessary . The railway nection o f the most important North Sea harbours and the indus­ projects will shorten e.g. the time for the journey from Hanover trial centres in the w est o f Germany with the areas o f to Berlin from 4 hours in 1992 to l3/,) hours. and Berlin can be considered most important. Urgent tasks are The improvement o f railway transportation not only is of na­ the rehabilitation o f the Mittelland canal and the Elbe ca­ tional importance; it also increases the attractiveness o f the rail nal and their upgrading to a European level. A particularly diffi­ system for the international traffic. A part o f the European high­ cult part o f this connection is the crossing o f the Mittelland canal speed network is the connection Cologne-Rhine/ Main. and the river Elbe near Magdeburg. With respect to the road The new railway line Cologne-Rhine/ Main will consid erably construction projects, the improvement -of the road conditions in improve the link between of the German Rhine/ Ruhr and

2091 for the journey will be approx. 58 minutes with the new high­ speed trains o f German Rail. An essential task for the realization o f this major project is the solution o f the geotechnical problems concerning the tunnels. The new railway line passes through 24 tunnels with a total length o f approx. 40 km. Four tunnels are built by cut-and-cover construction, 19 are built by underground construction with drill- and-blast driving, and one tunnel is built by underground con­ struction with mechanical heading. The majority o f the tunnel structures are situated in devonian, partly deeply weathered rock strata consisting o f alternating sequences o f claystone and sand­ stone resp. clayey slate and quartzite and in some sections also in quaternary and tertiary soils. The rock has a medium to narrow joint spacing. Furthermore, the rock strata are often displaced relative to one another at faults. The stability analyses o f the tunnel structures are carried out according to the finite element method. During construction, the stability of the tunnels is verified by in situ measurements. The interpretation o f the measured results is meant to lead to an improved assessment o f the rock mechanics parameters for the structural analysis, thus allow ing the adaptation o f the support to the actual rock conditions (observation method) (Wittke, 1997). Figure 45 shows a survey o f the geology in the area o f the tunnels o f the new railway line Cologne-Rhine/ Main. Finally, the "Stuttgart 21" transportation project shall be briefly presented here. It consists o f the restructuring o f the railroad Motorway Railway Waterway junction Stuttgart and the construction o f a high-speed railway Figure 43. Infrastructure projects, German Unification (from: line from Stuttgart to Wendlingen, which will form a part o f the Bundesministerium fur Verkehr, 1992). high-speed line from Mannheim via Stuttgart to Ulm (DB Pro- jekt GmbH, 1997). The main task o f this project is to rebuild Stuttgart central station as an underground station replacing the present terminus. This will enable a significantly faster connec­ tion to the German and European high-speed network. In Stuttgart and many other German cities, until no w the neces­ sary railway tracks have blocked the development o f the inner cities and separated urban districts. In Stuttgart, for example, reconstructing the central station and correspondingly leading the access tracks through tunnels within the urban area makes a connected inner city area o f more than 1 km2 o f former railway grounds available for high-grade development (Deutsche Bahn AG, 1995). Up to the year 2010, the scheduled train departures fro m Stutt­ gart will increase by approx. 50 %. In both directions, every 20 minutes a high-speed train (ICE/ ECE) will leave the new central station, amongst others on the European main line Mu- nich-Paris.

6. SUMMARY

This written version o f the Heritage Lecture on "State o f the Art and Development of Geotechnical Engineering in Germ any" held on the XlVth International Conference on Soil Mechanics and Foundation Engineering opens with a description of the be­ ginnings of foundation engineering in Germany, which are closely linked with the Romans. Many structures that can still be visited today in Germany bear testimony to the high standard o f bridge construction and hydraulic engineering already existing approx. 2000 years ago. Distance: 204 km In the following chapter 2, the development o f the funda­ 24 Tunnels: 40 km mental principles necessary for geotechnical engineering in the Time: 58 min fields o f mathematics, engineering mechanics, and hydraulics is Figure 44. High-speed railway line Cologne-Rhine/ Main (under depicted. Since scientists in Europe mutually influenced each construction). other, a detached reflection on the knowledge gained in Ger­ many is not useful. With KARL VON TERZAGHI, soil me­ chanics developed into an engineering science, which led to ex­ Rhine/ Main conurbations. It is o f importance for the European tensive research activities in Germany, too, especially concern­ high-speed network as it completes the network in the direction ing the testing technology for the description o f the mechanical o f Paris, Brussels and Amsterdam (Eschenburg, 1996). properties o f soils. These aspects are discussed in chapter 3. The railway line with a total length o f 204 km runs from Co­ Although the development of foundation engineering took logne along the motorway A3 through the Siebengebirge, place in parts simultaneously with the development of soil me­ Westerwald, and Taunus mountains into the Main plain to chanics, a separate chapter is dedicated to it. It become clear that Frankfurt resp. Wiesbaden/ Mainz. A fter the completion, the time many techniques applied world-wide today have their origin in

2092 Frankfurt

Umtxfo

Wies­ baden,

Rhein

Koblenz Mainz Legende Legende — Tertiäre Tone und Sande tertiary clay and sand mnmm: Quarztt quarzite *777: Rotllegendes perm ian Tn™ Abschiebung normal fault

?r—- Sandstein / Schluffstein / alternating sequence o f Tonschiefer d a y slate Tonsteln Wechsetfolge sandstone, siltstone -vvw Goete gneiss Aufschiebung upfa ult and mudstone Basalt b asa lt = Tonsteln mudstone

Figure 45. High-speed railway line Cologne-Rhine/ Main, geology.

Mannheim (NBS) C ologne

Feuerbach

'te Northern Station

Bad Cannstatt

Mittnachtstraße

Figure 46. Planned new central station Stuttgart (from: Deutsche rttlP: nr*~Si- - •:<* Bahn AG, 1995). S tation Central Station Untertürkheim

Germany. In chapter 5, some o f the developments in geotechni­ cal engineering in Germany after 1950 are described . Here, the NBS Ulm Rider/Tübingen German Geotechnical Society (DGGT) has to be mentioned, as it holds the central position in disseminating and coo rdinating the Airport/Munich research results gained in theory and practice in Germany. The large construction projects under way at present in Germany are NBS: Highspeed Railway Line in many cases linked with the German reunification. In this con­ text, the construction o f new transportation installations and the Figure 47. Some o f the tunnels within the urban area o f Stuttgart enhancement o f the existing ones, necessary for the former two (Deutsche Bahn AG, 1995). German states to grow together, plays an important role. W ithin the framework o f this paper, not all scientists, research institutes, inventions, or projects can be appreciated in the same Bauer 1997. International. Bauer Spezialtiefbau GmbH, Schro­ manner. In this context, especially the German read ers have to benhausen. be asked for their understanding. The objective o f the publica­ Buchholz, W. 1931. Erdwiderstand auf Ankerplatten. Jahrbuch tion is to offer the participants o f the XlVth International Con­ der Hafenbautechnischen Gesellschaft, Band 12, Hamburg. ference on Soil Mechanics and Foundation Engineering a survey Bundesministerium für Verkehr 1992. Verkehrsprojekte Deut­ o f the great tradition and the high level o f development of geo­ sche Einheit. technical engineering in Germany. Casagrande, A. 1964. K arl Terzaghi 1883-1963. Géotechnique, Vol. 16, No. 1, The Institution o f Civil Engineers, London. Coulomb, C. A. 1773. Essai sur une application des règles de REFERENCES Maximis et Minimis à quelques problèmes de statique , relatifs à l 'Architecture. Mémoire Académie Royale des A tz, P., Schmidt, H.G., Seitz, J. & Semprich, S. 1991. Grund­ Sciences, Paris. bau. Beton-Kalender, Teil II, Verlag Emst & Sohn, Berlin. Culmann, C. 1866. Graphische Statik. Verlag Meyers und Zeller, Bauer 1996. Bohrpunkt, Nr. 24. Bauer Spezialtiefbau GmbH, Zürich. Schrobenhausen. Deutsche Bahn AG 1995. Das Synergiekonzept Stuttgart 21,

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