Geotechnical Models of the Arch Foundations of The
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r Rudarsko-geoldko-naftni zbornik Vol. 10 str. 83-88 Zagreb, 1998. UDC 552.1:624.131:624.2 Immi znanstveni Cfunak GEOTECHNICAL MODELS OF THE ARCH FOUNDATIONS OF THE MASLENICA BRIDGE Tomislav NOVOSEL', Eduard PRELOGOVIC~and Tomo NOVOSEL~ '~nstituteof Geology, Sachsovu 2, HR-10000 Zagreb, Croatia '~acultyof Mining, Gcol and Petrolettrn Engineering University of Zagreb, Pierott~jeya6, HR-IOWO Zagreb, Croatiu Tivilengineering institute, J. Rahde I. HR-IMW Zagreb, Croatia Key-words: Engineering geol ical characteristics, Foundation of Kljuhe rije-ti: InienjerskogeoloSke mahjke, Temeljenje mosta, the bridge, Geotechnical models~tructucaltectonic relationships GeotehniEki modeli, Strukturno-tektonski odnosi On the site of Maslenica bridge structural tectonic, geophysical and engineering geological investiations, ~eotcchnicaldrilling and lab- Na lokaciji MasleniEkog mosta uradcna su strukturno-tektonska, rat& samDG tes6nm were oe~formed:~aslenicaanticlinz is charac- gcofizitka i inZcnicrsko~eoloSkaistraiivania. istraina buSenia i labora- terisdc fo; the investigated area. It is built from the limestone of Cretaceous a e. The anticline has an asymmetrical form with the MGleniEia antiklinala. Izgradena jc od ;apnenaca kredne starosii. vergence of tie axial plane towards thc north. Reverse faults with Antiklinala ima asimetrihn oblik s vergencljom osne ravnine prema recent activities are present. The recent activity was proved by the sjeveru. Prisutni su reversni rasiedi s recentnom aktivn0.X~.Recentna discovery of the broken stalactite with the displacement of 11 cm, aktivnast dokazana jc nalazom-presjeEene sige s pomakom od 11 cm, whose age is 36000 years. On quite young stalactites (stalagmites) in tiia starost ie 36000 cod. Na sasvim mladim sigama u Soilii na za~adnoi the cave on the west side, no displacements were noticed. For the next sirani nisu i&ni Smaci. Za povratni perid od 50dgi;dina $ogn& podof 500 years the maximal possible displacetpent of 2.0 cm is ziran je moguCi ~aksimalnipomak velltine do 2,O cm. Manje Spilje oreseen. Smaller caves with the dimensions of 1 m-, were formed on dimenzija do 1 rn' nastalc su na presjeciStima reversnih rasjeda i veCih the intersections of the reverse faults and greater joints. The canyon pukotina. Kanjon Novsko Zdrilo nastao je u zoni smicanja rasjeda s Novsko Zdrilo was formed in the fault shear zone with tectonic trans- dcsnim tektonskim transportom. port to the right. Prema stupnju razlomljenosti izdvojene su inienjerskogeoloSkirn According to the range of fracture, three characteristic types of rock istraiivanjem tri karakteristizne sredine. Prema nGeomehaniEkoj masses were separated by en ineering geological investigations. Ac- klasifikaci'iu (RMR) prva sredina odgovara 11. do 111. Masi, druga mrding to ~Geomechanicalcfasificatlona (RMR) the first sredina odgwara IV. klasi, a trefs sredlna odgovara V. Wasi (milonit). responds to I1 to 111 claw, while the second type cornsponds toKg1 Originalne inienjerskogeolo5ke podloge nisu omoguCile, zbog and the third type corresponds to V class (mylonite). sloienosti grade terena, direktnu primjenu u analizi odnosa naprezanja Because of the comp cxity of the terrain structure, original cngi- i dcformacija. Zbog toga su izradeni simplificirani geotehnitkl modeli. neering geological bases of design have not enabled the direct applica- Oni su omoguBli projektiranje temeljenja u stijenskoj masi i saniranja tion of the analysis of stress-strain behaviour. Because of that the dijelova slabe kvalitete. sim lified potechnical models were done. They enabled the projecting of iundabon in the rock mass and renewal of poor quality rock mas. Introduction Maslenica bridge is built over Novska idrilo the nar- unit (Ravni kotari) and Dinaric one (Mt. Velebit). Fault row channel which connects Velebit channel and Novi- zone is seismotectonically active. grad sea. Total length of the bridge is 300 m. The arch Tectonical structural measurements showed two peri- overlaying Novsko gdrilo is 200 m. The building of bridge ods of forming of local structures surrounding Novsko wasprecededbylargeinvestigation(Novoselet al., idrilo (Kuk et al., 1994,PrelogoviC et al., 1994,V r k 1j a n e t a 1 ., 1994,And r iC e t a1 ., 1994). 1995). During the older period the folding of sediments It was necessary to determine in details structural geol- began. The anticline with NW-SE orientation is formed ogy, sesimotectonic and engineering geological proper- ties on the site of the bridge. The necessary bases of design for rock foundations were made (Ku k e t a 1., 1994, MulabdiC et al., 1994, Novosel et al., 1994). But, explicitly unhomogeneous and anisotropic rype causes that bases of design, in their original form, have not made possible prognostic analyses of the rock mass behaviour during the excavation and after the building of foundation. Therefore, simplified models of geological properties on the sites of foundations were made. Simplified geotechnical model was made on the site of foundation, which enabled analyses of stress- strain behaviour in the interaction between future bridge foundations and rock mass (V r k 1j an e t a I. , 1994). Geological, seismotectonical, engineering geological and geophysical data On the surface, there are carbonate sediments of Creataceous age (Iva noviC e t a l., 1973; 1976). In the structure area. the site of the bridge is laced on the boundary of the ~elebitfault zone (fig. 2;). This is the boundary fault of two regional structural units: Adriatic Fig. Mas'enica Rud.-geol.-nafi.zb., Vol. 10, Zagreb, 1998. 84 Nowsel, T., PrelopviC, E. di Novaref, T.: Maslenica bridge Fig 3. East side of Novsko idrilo Fig. 2. Local structural relationships Le end: 1 -kticline axiq 2-~eversefaults;3-~onnal faults; 4-~ault.. with horizontal movemenc 5 - Local stress; 6 - Local extension of Novsko Zdrilo; 7 - Fault zones .l .ahlc 1 I<ock mass c;~tcgorisation ;~ccorctingto "Cicomcchanical c1;lssil'ication" (simplified motlc I) (I%icniawski. 1 970) CI-IARACTEKISTIC' VAL1 IES FOR DIFFERENI' I DESCRIPTION OF PARAMETERS TYPES OF 1IOC:K MASS TYPE I TYPE I1 I TYPE 111 A l I JNIAXIAL C'OMPKESSION 151 MPa 68 MPa ;z 1 MPa STRENGTH OF THE SPECIMEN NI IM BER OF POINTS 12 7 1 ,:\i I lNl)lil<(il<OlIRl) WA'l'l:l< wct-dry \vc~-clry \\YI sccpacc sccpaec NI lMl<l3<01.. l'0lN'I.S I0 I0 7 .I\(> OI<II~N'I~A'I~ION01.' l)lS('ON'l'I- satisfyilly sat isly i~~g sat isl'yilli~ Nt 1l'l'Il:S (~OLIII(~:I~~OIIS) NI JMI<I3<01: I'OIN'I'S -7 -7 -7 Nt lMl3l:l< 01.' ('\,ASS I 11 - 111 I V V ('I IAI<A~"I'I~~I<IS'I~I~'01.' l<O('K MASS I lard rock 111ass I .lollltcd rock 111ass I So11 Rud.-geo1.-naft.zb., Vol. 10, Zagreb, 1998. Novosel, T., Prelogovid, E. & Novosel, 2: Maslenica bridge 85 stalactite with displacement of 11 cm was found. Using c14radiometric method the accurate age of 36000 years was established. Novsko idrilo channel was formed in the zone of horizontal fault with tectonic transport to the right. Orientation of the local stress has shown the re- cently present movements in that fault zone (Fig. 2b). Generallv. west side of Novsko idrilo is structurallv more stabile t6en the east side. On that side there he less I marked fault zones filled with mylonite material. How- = ever, on both sides, there are highly jointed zones with the width of a few meters (Figs.w 3.4).,, Engineering geological hvestigation showed specially 1 big differences in rock mass aualitv (I S R M . 1976: lee re, D. U. & Deere, D. w.: 1988):~ighly crushed zones are related to faults. Occasionally, wide mylonite zones occur. Along with shattering mylonite formed during the compression, there are shear mylo- nites highly enriched with high plasticity coherent mate- Fig. 4. West side of Novsko Mrilo rial with. Pale blue colour of those mylonites, opposite LEGEND: Drawing of fhe arch foundation Fig. 5. Geotechnical model of the arch foundations on the east side of Novsko idrilo accompanied by reverse faults SW vergence. Joint sys- to brownish yellow colour of surrounding material, tems characteristic for compression regime appearing shows the recent activity of faults. Because of the shear also. A set of normal faults occurred towards the Velebit processes along particular fault systems, existence of thin fault (Fig. 2b). During younger (and recent) period dis- plated blocks was noticed, together with the debris and continuous change in local stress orientation to NS small grain sized material or clayey-silty material. The direction was noticed (Fig. 2c).The anticline structure is most important general conclusion is the emphasised deformed into asymmetric shape with axial plane ver- influence of tectonic processes and wathering to the rock gence towards north. The fault systems with horizontal mass, which is explicitly unhomogeneous and anisot- displacemnt were specially active. On several places, on ropic(Novose1 et al., 1994). the intersections with the layers, cavities and caves were Homogeny and isotropy of the rock mass was possible formed, which were lately filed with Quaternary sedi- to define, thans to wide geophysical survey (shallow ments. Occurrence of faults with vergence towards north reflection and refraction, down-hole and cross-hole is significant. The proof that the faults have recently measurements, and measurements of seismic waves by been active are foundings of the stalactites inside their polar method on the slopes, using the boreholes) (An - zones. On the eastern side of Novsko idrilo the faulted d r i C e t a 1 ., 1994). The logging of borehole was per- Rud.-gwl.-naft. zb., Vol. 10, Zagreb, 1998. Novo.re1,T., PrebgoviC, E. & NovoseI, T: Maslenica bridge tact zones foundations - rock mass. Geotechnical mod- els were shaped on the sites of arch foundations because the greatest concentrated stress of the future object on rock mass were foreseen there. On the east side in the area of arch foundation, diago- nal to the sides of the rectangular ground-plan of the basis surface, there is the mylonite zone (material C) of the reverse fault zone parallel to the layer position Figs.