INTERNATIONAL SOCIETY FOR SOIL MECHANICS AND GEOTECHNICAL ENGINEERING
This paper was downloaded from the Online Library of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). The library is available here: https://www.issmge.org/publications/online-library
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. Geotechnical Aspects of Construction of the Shinkansen Aspects Geotechniques de la Construction du Shinkansen
M.FUJII Dr. of Engineering, Former President of Japanese National Railways
SYNOPSIS The geology of the Japanese archipelago is characterized by highly complex topo graphy and unstable ground. Approximately 70 percent of the country is mountainous, and about half of the land transportation is therefore dependent on railways.
The Japanese National Railways, which covers the vast majority of this rail transport, has carried on construction of the Shinkansen express train system since 1958. The author has been engaged in the Shinkansen project from the planning stage.
This paper presents an outline of Shinkansen construction, including the methods employed in solving the various problems arising in the design and construction of earth structures, foundations for concrete structures, and tunnels, and the stabilization of weak ground, taking into consideration the soil and geological characteristics encountered during the construction process.
1. INTRODUCTION formed by folding action and volcanic ac tivity and is surrounded by the sea. About I am highly honored to have this opportu 70% of the total area is of mountainous nity to deliver a special lecture to the topography and the remaining narrow plain many experts from all over the world who is divided up into even smaller portions are participating in the 9th International by mountains. In this small area lives a Conference on Soil Mechanics and Foundation large population of 110,000,000. Engineering. Such geographical features result in pas In this lecture, I would like to give an senger and freight transport conditions outline of the Shinkansen, in which I have not found in other countries. The degree been involved since the planning stage, of dependence on the railways for passen and also to discuss Japanese geological ger transport is extremely high. This is and soil features and how the various prob because of the high population density in lems they posed in the construction of the urban centers and the use of railways for Shinkansen were solved. Naturally, a wide urban transport, especially worker and range of technology from many fields in student commuter transport. Medium- and cluding civil, mechanical and electrical long-distance passenger flow routes are engineering was called on in the construc limited and the main flow is concentrated tion of the Shinkansen, but I would par in lines running the length of the country. ticularly like to explain the achievements On such routes, railways are the most in geotechniques and tunnelling engineering suitable means of mass transportation. As to overcome the many adverse conditions can be seen in Fig. 1, the share of pri such as the variable topography and geol vate automobiles in passenger transport ogy, heavy rainfall and weak ground. (passenger-kilometers) is expanding re markably, but the dependence on railways I also hope that this lecture will be of still reaches a total of 45% for both some assistance in increasing your under national and private railways (as of 1975). standing of the status quo in Japan. In the case of freight transport, there is a very high dependence in total ton-kilo- meters on domestic shipping because almost 2. RAILWAYS IN JAPAN AND THE CONSTRUCTION all of the raw materials for industry are OF THE SHINKANSEN imported via seaports and industrial sites are nearly all located in coastal areas. 2-1 Railways in Japan Railway freight transport has levelled off on the whole because of the effects of Japan is a long, narrow island country decreased domestic production of coal, and the share has been going down in recent was adopted for the following reasons on years because of the advances made in truck the basis of the results of various inves transport. However, a total of 13% of all tigations : freight transport depended on the railways in 197 5 (Fig. 2). (1) Through the integration of new and exist ing lines, the best system to suit various In consideration of future traffic prob types of transport demand and the highest lems in Japan, the advantages of rail total transport capacity can be obtained. transport will no doubt increase when viewed from many aspects including conser (2) The functions of the new and existing vation of power and energy, more efficient lines can be separated and simplified so land utilization, savings in manpower and that costs are actually lower in the long environmental preservation. term.
The great majority of this rail transport (3) In the new lines, the most modern is handled by the Japanese National Rail technology can be applied independent ways which has 21,000 working kilometers of existing facilities and maximum safety of existing narrow-gauge lines throughout can be achieved even at high speeds. the country. The daily train operation rate is 1,900,000 train-kilometers. In Construction on the first Shinkansen, addition, there are also 1,070 km of the 515.4 km between Tokyo and Shin-Osaka, Shinkansen line (standard gauge) which started in April 1959 and the line was will be described later. opened in October 1964. Thereafter, in 1972 this line was extended 164.4 km west Currently, a daily average of about 19 mil to Okayama and in 1975, 397.9 km further lion passengers and about 400,000 tons of west to Hakata. The Shinkansen now runs freight are transported. To cope with through not only the most populous parts future demands, various measures are being of the country but also the areas most promoted to increase transport capacity important politically, economically and quantitatively, improve the quality of culturally. It connects the nation's rail transport service and achieve moderni largest cities and has a total length of zation . about 1,0 70 km. The number of passengers using the Shinkansen has increased remark 2-2 Shinkansen Construction ably year by year and by May 1976, after about 12 years of operation, the number There are many items involved in the im of passengers exceeded one billion and provement of rail transport but the most the Shinkansen was considered to be indis wide-ranging goal is the construction of pensable to our daily life (Fig. 3). At the Shinkansen which can be considered as present, three new Shinkansen lines total the most fundamental and largest in scale. ing about 835 km are under construction: the Tohoku Shinkansen (approximately 500 Construction of the Shinkansen was started km between Tokyo and Morioka), the Joetsu because it was anticipated that the trans Shinkansen (about 270 km between Omiya portation capacity of the Tokaido Line, and Niigata) and the Narita Shinkansen the most important line in Japan, would (about 65 km between Tokyo and the New reach its limit before long. This system Narita Airport). Several new routes for
Passenger Transport (billion) Freight Transport (billion)
Fig. 1. Share of Passenger Transport Fig. 2. Share of Freight Transport in Japan in Japan which construction is planned are now under investigation. The undersea tunnel (2) Mode of motive power linking Aomori and Hakodate and the bridges connecting Honshu and Shikoku In electrification of existing lines, both will also constitute a part of the Shin- 1,500 V direct current and 20,000 V alter kansen network. Such a high-speed railway nating current are used, but for the Shin network will contribute to the balanced kansen 25,000 V alternating current was growth of the country and the furtherance adopted. of the people's welfare (Fig. 4). (3) Mode of electric traction
A comparative investigation of two prospec 3. OUTLINE OF THE SHINKANSEN tive modes, electric-locomotive traction and the electric railcar train, was con 3-1 Basic Plan ducted. The mode of the electric railcar train was chosen because the motive power can Because of the pressures of competition be dispersed over many axles of the rolling from automobile and air transport, it has stock, the great cohesion between wheels been felt that new railways should utilize and rails necessary to high speeds can be technical innovations to the utmost in obtained, and there are no large concen order to revitalize declining rail trans trated loads which would require greater port. On the basis of this concept, the strength of the structures. This decision items forming the basic plan for Shin- reflects the good results and experience kansen construction were decided as fol obtained in electric railcar train opera lows : tion on existing lines.
(1) Gauge of track (4) Train speed
Existing lines have a narrow gauge of On the basis of research performed by the 1,067 mm and one major decision faced was Railway Technical Research Institute, it whether to retain this narrow gauge or was decided that the maximum speed should adopt the 1,4 35 mm standard gauge for the be such that the train would make the 500 Shinkansen. Although there were many km journey between Tokyo and Osaka, Japan's transport-related advantages in the use two largest cities, in 3 hours. The maxi of the narrow gauge which would permit mum speed was accordingly set at 210 km/h the access of rolling stock to both the with the possibility of its being raised to new and existing lines, the transfers be 260 km/h in the future. tween the two lines would become complex, costs would increase and complete moderni Various tests were conducted concerning zation of the new line would be almost the maximum speed, and in February 1972 a impossible. In addition, if the narrow world speed record of 286 km/h was set gauge were used, it would have to run with a 951-type test train, confirming through heavily urbanized areas to gain that an actual operating speed of 260 km/h its advantages. But this would make con is feasible. struction very difficult and could create environmental problems after the line was opened. Therefore, it was decided to build a separate, standard-gauge line, from which passengers could change to existing lines only at the main stations. Legend
■ ■ ■ In operation (1,074km)
—■ ■ -r Under construction (835km)
'■■■■ To be constructed (approx. 1,520km)
= = Proposed (approx. 3,500km)
N o. of Passengers C a rrie d (m illions of persons)
1976 O ct M arch M arch 1964 1972 T okyo-Shin-Osaka Shin-Osaka-Okayama Okayama-Hakata line opened line opened line opened Fig. 3. Sninkansen Passenger Fig. 4. Map of Nationwide Shinkansen Transport Figures Lines (about 7,000 km) As part of its system of countermeasures, (5) Signal safety and operation control in 1975 the Environment Agency issued system the environmental standards and execution target periods for noise as shown in Safety is one of the most important factors Table 2. The Agency also set the maximum in high-speed transport. For the Shin- vibration level at 70 dB and recommended kansen, complete signal safety is achieved that countermeasures be taken for levels by the use of automatic train-control in excess of that. equipment, centralized traffic-control equipment and supporting computer equip For some time, the Japanese National Rail ment. In the automatic train-control ways has been taking measures to prevent equipment, a current with frequency cor noise and vibrations through noiseproofing responding to the speed level flows in the for plate girder bridges, provision of track circuit. This is received by the noise insulation fences for tracks on rolling stock and indicated in the cab banks and viaducts, making rails heavier, signal device. When the train speed ex inserting rubber mats under the ballast ceeds the specified speed, automatic and improving the structure of the rolling application of the brakes slows the train stock. These measures are being promoted to the specified speed or below. There are six speed stages, including a zero indication when the train is stopped. Table 1. Shinkansen Construction Stand The centralized traffic control (CTC) ards and Main Specifications equipment is located in the Central Control Station in Tokyo. It monitors all of the Tokaido From the Sanyo trains on the entire line, gives out in Description Shinkansen Shinkansen on structions and performs remote control of turn-outs in each station. Planned Max. 26 0 km/h Speed The computer equipment, known as COMTRAC, automatically compiles train operation Max. Speed 210 kg/h 210 km/h diagrams and performs train route control, operation adjustment, coach allotment and 2,500 m 2,500 m information communication. This makes Min. Curve ,000 possible safe and smooth train operation Radius (4 m or more in with a minimum head of 5 minutes. principle) 3-2 Construction Standards Max. Gradient 20/1,000 15/1,000
Table 1 shows the construction standards Min. Longi and main features of the Tokaido and sub tudinal Curve 10,000 m 15,000 m sequent Shinkansen lines. Radius
3-3 Environmental Protection Track Center 4.2 m 4.3m Interval Immediately after the Tokaido Shinkansen went into service in 1964, wayside resi dents started to complain of noise and Rail Weight 53.3 kg/m 60.8 kg/m vibration caused by operation of high speed trains; this later became a social Standard P16 P17 problem as the awareness of pollution Live Load (Sanyo: P16) increased in Japan.
Table 2. Shinkansen Noise Prevention Targets
Target achievement periods Shinkansen wayside Period for Period for existing Period for new regions Shinkansen lines Shinkansen lines Shinkansen lines under construction Region of 80 phons a Within 3 years At time of opening or higher
i Within 7 years Region of 7 5 to Within 3 years b At time of opening from opening 8 0 phons ii Within 10 years
Region of 70 to Within 5 years c Within 10 years 75 phons from opening in keeping with these regulations, and of soil brought from the mountains regions peripheral measures for wayside dwellings, (Table 3). Although the Japanese archi etc., such as noiseproofing and removal pelago has a total area of only 370,000 km2, have been started. it includes the following features:
Currently, noise can be kept to 80 phons (1) The mountains are generally high. or less at the boundary line of the right- of-way but continuous efforts are being (2) The mountainous area occupies a very devoted to the improvement of environmental large portion. protection by developing new technology. (3) The plains are separated and isolated by the mountainous areas.
4. TOPOGRAPHICAL AND GEOLOGICAL FEATURES (4) The topography and geology are complex OF JAPAN and weak.
4-1 Topographical Features of Japan The topographical regions of Japan are shown in Fig. 5. The Japanese archipelago consists of Hok kaido, Honshu, Shikoku, Kyushu and many 4-2 Geological Features of Japan smaller islands forming an arc. To the west of the archipelago lies a compara The geological structure of Japan is full tively shallow ocean basin including the of variety and highly complex, but in a Japan Sea between the islands and the broad perspective the country is divisible continent. To the east is the Pacific into several geological regions by means Ocean with ocean troughs such as the of geological structural lines. Japan Deep and the Ryukyu Trough with depths exceeding 10,000 m. Typical structural lines in Japan are the line from Shizuoka to Itoigawa and the The Japanese islands belong to the Circum- Median Line. In addition to these, there Pacific orogenic belt which surrounds the are many other structural lines and faults. Pacific Ocean and includes the Rocky and Fault topography such as fault valleys, Andes mountain ranges. Since volcanic and fault basins and horst mountains can be seismic activity and crustal movements are severe, topographical and geological condi tions are highly unstable. In Japan, there are many high mountains of ! 1 2,000 to 3,000 m in ranges such as the // i f mh* Japan Alps, and mountainous regions account for about 70% of the total area. Since yi there are also regions with some of the 1 highest rainfall and snowfall levels in the Low land 1 world, the mountainous regions are eroded Volcanic by flooding. A large portion of the allu f 111» region vial plain has been formed by the deposition | High land f
Table 3. Main Topographical Areas in Japan
Area Ratio v Æ iîi 1 1 (km2 ) (%) Mountainous 203,713 55 districts
Source: Data of the Geographical Survey Fig. 5. Geomorphological Regions of Japan Institute (M. Watanabe, 1961) observed in various places. Because of coast are predominantly drowned valley breakdown and softening of the bedrock in deposits (Table 4). The regions which these faults, such phenomena as sudden include background swamps, deltas, drowned spring water and abnormal earth pressure valleys and remains of lagoons form very occur in tunnelling work. weak ground which makes a bad foundation for structures. The southwest region of Japan to the west of the Ito-Shizu Line is divided into inner Fig. 6 shows the basic geology of Japan and outer zones by the Median Line. The which has been outlined above. outer zone in southwest Japan (Kii, Shikoku and Southern Kyushu) is in the form of band-type strata running parallel to the Median Line and consisting of a paleozoic 5. CONSTRUCTION OF THE SHINKANSEN WITH group, mesozoic group, tertiary system, RESPECT TO JAPANESE TOPOGRAPHICAL AND crystalline schist and sedimentary rocks GEOLOGICAL FEATURES in the order of the geological ages. 5-1 Outline of Shinkansen Structures The inner zone of southwest Japan (Hokuriku, Chugoku and Northern Kyushu) consists of (1) Basic concepts of Shinkansen structural granitic rocks and gneiss, and scattered design sedimentary rocks of the paleozoic or mesozoic groups, tertiary system, etc. The following are the basis concepts of Shinkansen structural design: The northeast zone of Japan located to the east of the line between Itoiqawa and (a) Since the permissible error for track Shizuoka has no clear geological struc maintenance must be very small because of tural lines,but the main strata of vol high-speed operation, sufficient considera canic tertiary rock (mudstone, siltstone, tion must be paid in the construction to tuff and sandstone) to the west of the minimizing the track maintenance work. central backbone ridge (Japan Sea side) are known as the green tuff zone. This (b) Because the electric railcar train is geology is typical of Northeast Japan and used, there are a great number of equal is also distributed on the eastern side axial loads,and careful consideration must of the Ito-Shizu Line, in the inland area to be given to decreases in material strength the east of the backbone ridge and on the due to fatigue. Japan Sea side of the inner zone of South west Japan. Since this green tuff is weak (c) Since the maintenance time for the and shows remarkable expansion and the railway structures is limited to a few unconsolidated rock is water-bearing, many hours during the night because of the high problems such as face failure and soil speed operation, consideration must also outflow occur in tunnels. This geology be given to reducing the maintenance work also results in landslides on the surface. required for the railway structures them selves . Another important feature of the topogra phy and geology of Japan is the many recent (d) The structures must have a form and volcanoes scattered throughout the country. construction which minimize noise. The geology of volcanic regions consists of lava and pyroclastic rocks or volcanic (e) The design must take into consideration ash. These form a large aquifer stratum the longitudinal load from the long rails, and the rock may be changed by the action vibration due to high-speed operation, etc of hot springs (forming solfatric clay or propylite), so that many problems arise (f) The construction must be simple with a just as in the green tuff zone. modern appearance.
This has been an outline of the geological (2) Topographical and geological conditions structure of the main mountainous regions. along the Shinkansen and structural The hill and terrace regions are formed types mainly of quaternary diluvial deposits which consist of strata of terrace gravel To achieve contact between the Shinkansen with a low degree of solidification, and conventional lines, the construction marine and lacustrine clay and sand. route was selected so that it made contact There are also many volcanic ash strata with the main stations of conventional several meters thick in the surface areas lines. The conventional lines run through of northeast Japan, Kyushu and Hokkaido. old towns and villages located in coastal sand dunes, fans, piedmonts and other areas The low ground on the shores of the sea with good ground conditions. and rivers consists of alluvial deposits accumulated in recent times. These de While the Shinkansen must make contact with posits contain unconsolidated gravel, conventional lines at the main stations, sand and clay. in other regions the route must be lo cated so that densely populated areas and The alluvial deposits which compose the existing facilities are avoided as far as alluvial lowlands bordering on the sea possible. Because of the necessity of a Table 4. Alluvial Lowland Topographical Regions, Soil Quality and Ground Conditions
Ground sur Topographical Soil Ground condition Topography N face slope characteristics quality value Quality
A Fan 1/1,000 or Concentric contour line, Coarse 30 or Excellent more net flow, underflow gravel, sand more
B Natural 1/1,000 - Band-type protrusion of Sandy soil 10-20 Rather levee 0.2/1,000 contour line, villages, good band-type arrangement of farmlands
C Background 0.5/1,000 or Low flat paddies among Clay, silt, 10 or Rather swamp less the same topography as fine sand, less bad above peat
D Delta 0.2/1,000 or River mouth inside calm Fine sand, 10-4 Bad less bay thick clay or alluvial less deposits
E Flood plain 1/1,000 or Almost parallel contour Gravel, sand 20 or Good with large more lines, net-type flow more amount of earth and sand
F Drowned 0.2/1,000 or Drowned valley paddies Clay, silt, 4 or Very bad valley less with little flow peat less
G Coastal bar Band-type elevation Sand, 15 or Good parallel to seacoast gravel more
H Remains of 0.2/1,000 or Paddies, etc., with bar Clay, silt, 4 or Bad lagoon less background peat, fine less sand
Fig. 6. Geological Map of Japan large radius of track curvature, etc., im tunnels, viaducts and bridges because of posed by the high-speed operation, there the severe construction standards for are many cases where it must pass over poor radius of curvature, maximum grades, ground in the plains. grade-separated crossings in all cases, etc., unfavorable topographical features In the 515 km between Tokyo and Shin-Osaka, with many mountains, conditions in the about 85% of the total area consists of regions along the lines, etc. However, alluvial and diluvial deposits and there in the Tokaido Shinkansen where the con are many areas with very weak ground formed struction started, the length of earthwork in recent times. Among the alluvial de such as earth cutting and filling exceeded posits, regions with weak ground showing 50% of the line. N-values of the standard penetration test of 5 or less extend for about 70 km and In the Shinkansen lines constructed after very weak ground with N-values of 0 to 2 the Tokaido Shinkansen, the proportion of consisting mainly of peaty soil, about 15 earthwork has decreased greatly because, km. in addition to the differences of condi tions in the regions along the lines, it Table 5 shows the types of structures for is generally cheaper to construct concrete the Tokyo-Hakata Shinkansen (about 1,070 km) viaducts than to make earthbanks of large now in operation and the approximately 860 width, considering Japan's extremely high km of new Shinkansen lines now under con land prices. struction between Tokyo and Morioka, Tokyo and Niigata, and Tokyo and Narita. As this Fig. 7 shows the general structure of table shows, there is a large proportion of Shinkansen tunnels and viaducts.
Table 5. Comparison of Structure Ratios of Shinkansen Structures
Tunnels Embankments Bridges Viaducts Total Struc Struc Struc Struc Section length Qty. ture Qty. ture Qty. ture Qty. ture (km) (km) ratio (km) ratio (km) ratio (km) ratio (%) (%) (%) (%)
Tokyo-Shin-Osaka 515 68 13 275 54 57 11 115 22
Shin-Osaka-Okayama 165 57 35 12 7 14 8 82 50
Okayama-Hakata 400 218 55 82 20 14 4 86 21
Tokyo-Morioka 496 113 23 26 5 68 14 289 58
Omiya-Niigata 270 105 37.7 2 0. 3 30 11 133 49
Tokyo-Narita 65 12 18 18 28 5 8 30 46
Total 1,911 573 30 415 22 188 10 735 38
V ia d u c ts
Section B-B Section C—C Section D -D
Fig. 7. General Drawing of Shinkansen Tunnels and Viaducts of the Shinkansen. Therefore, the follow ing standards were adopted to prevent mud 5-2 Earthwork for the Shinkansen pumping in subsequent Shinkansen lines on the basis of soil tests conducted in areas For the cuts and banks of the Tokaido where mud pumping occurred along the Shinkansen, careful consideration had to Tokaido Shinkansen: be given to the following items, particu larly in design and construction,because (i) The soil shall contain at least 10% of the weak subsoils and the high-speed soil particles which pass through a 74 operation of the trains: micron mesh.
(1) Elimination of mud pumping (ii) The soil shall contain less than 70% soil particles which pass through a 420 (2) Prevention of sinking of ballast micron mesh.
(3) Prevention of settlement due to con (iii) The liquid limit shall be 35 or less. solidation of the bank after completion (iv) The plasticity index shall be 9 or (4) Keeping the amount of dynamic settle less. ment during train passage within the per missible limits. The causes of the slope failure included the difficulty of tamping the face of the As can be seen in Fig. 8, liquid limits of slope with machinery, especially at the wL < 50, wl < 75, CBR > 10 and CBR 2 5 top or shoulder of the slope. Therefore, were adopted as standards for Items (1) in subsequent Shinkansen lines, it was and (2) and, as shown in Fig. 9 , a coef decided to make the grade of the slopes ficient of subgrade reaction of K75 > 3 1 :1.8 in order to enable mechanical tamping kg/cm3 was adopted as standard for Items of the slope, to increase the safety factor (3) and (4). and to facilitate the slope work.
The main problems with cuts and banks Settlement of banks on weak ground was the found after the opening of the Tokaido result of insufficient preloading periods Shinkansen were as follows: due to delays in obtaining the land. In subsequent Shinkansen lines, it was decided (i) Frequent occurrence of mud pumping to assure sufficient preloading periods in areas of banking on weak ground and, in (ii) Failure of slope faces due to rain cases where there is no time for such pre- loading, to use viaducts. (iii) Settlement of banks in areas of poor ground The causes of settlement of bridge approach banks were that the bridge approach banking (iv) Settlement of bridge approach banks. was performed inadequately and later than the abutment work and unscreened gravel was The causes of these defects and the meas used as the banking material with the re ures taken to prevent them in subsequent sult that the sand portion was later washed Shinkansen lines are outlined below. away by rain, leaving voids in the bridge approach banks. Therefore, in subsequent Mud pumping occurred over a length of Shinkansen lines, it was decided to design about 24 km within the first year after the bridge approach banks for greater ease the line went into service and was largely of construction and to use materials which attributable to the high-speed operation include binders.
Fig. 9 shows the bank design used in sub sequent Shinkansen lines based on the experience obtained with the Tokaido Shin kansen .
Regulation of Material and degree of compaction The majority of the banking materials for Regulation of Degree of the Shinkansen consist of soil obtained com paction from diluvial terraces and tertiary hills Regulation of the method of as well as various types of tunnel debris com paction consisting of volcanic and igneous rocks, spreading flatly before paleozoic groups, tertiary systems, etc. the compaction
One feature of the Tokaido Shinkansen (between Tokyo and Shin-Osaka) in. the Fig. 8. Construction of Tokaido Shinkansen part east of Fujigawa is that it was necessary, mainly for economic reasons, to use a volcanic ash soil with high water content known as Kanto loam (natural water content and liquid limit: 60-180%; plastic- ity index: 10-90) for earthwork. In and rate of settlement after the trains addition, river sand with uniform grain start operating be within the range which size as shown in Fig. 10 was used inside permits maintenance. The safety factors the banks in the central part of the Nobi with respect to breakdown were selected Plain and composite earth fills with the as not less than 1.2 during banking and section shown in Fig. 11 were prepared. not less than 1.4 after operation starts. The permissible settlement one year after starting operation was set at not more than 10 cm in consideration of track main 5-3 Banking of Weak Ground for the Shin tenance capacity using ballast. kansen The safety factors with respect to break down are expressed as the ratio of the In the construction of the Shinkansen average shearing strength of the actual lines, bankings in weak ground areas were weak ground to the critical shearing most frequent between Tokyo and Shin- strength (cohesion) which the weak ground Osaka. The majority of the weak ground in requires for stable banking. The lower this zone resulted from peat formation in limit value was set as 1.4 out of consid swamps in the remains of drowned valleys. eration of the creep of cohesive soil, Also more cases of weak ground were found etc. in valleys with small rivers between hills or terraces rather than along large rivers. The allowable amount of settlement was decided from track maintenance limits and The peat, organic silt and clay which are economic considerations as follows. When the main constituents of the strata form the permissible limit value of the verti ing the weak ground generally have a water cal curvature of the track between the content and liquid limit of 100-400%, a weak ground banking which settles and the plasticity index of 50-250 and a void structure (mainly abutments) which does ratio of 2-12. The unconfined compressive not settle is considered to have a radius strength is in the 0.1 to 0.5 kg/cm2 range. of 8,000 m,mainly from the viewpoint of The thickness of this weak ground is often passenger comfort, the permissible amount about 10 m but there are locations with a of settlement is 2 mm. When a track cor maximum thickness of 50 m. rection is made once a week, the annual permissible amount of settlement becomes: In the design of banking on weak ground, it is essential that there be no failure 2 mm/time x 50 times/year = 100 mm per year. of the ground during banking, that the necessary safety factor be maintained This figure gives the approximate standard after the line opens, and that the amount for the permissible settlement rate in the
Roadbed 1. Including 10% or more grains which pass through standard 74 mesh m aterials u Slope surface materials 2. Including 70% or less grains which pass through standard 420^ mesh j Including 30% or more fine-grained soil 3. Liquid lim it 35 or less of grain size of 74*, or less F L^ ' Plastic '“ »t 9 or less Degree of compaction 300 m m ______90% or more of JIS A 1211 Banking materials 90% or more of A group 1GC.GM.CL.GW.SC.GP JIS A 1210 Degree of compaction , SM,SW,hard rack muck A and C groups Banking materials 90% or more of (Degree of Same as A group or B and C groups above JIS A 1210 or m ore compaction of banking^rr’ B group OL.CH.MH.OH.loo'se rock muck B group qc>5kg/cm’ ■ ‘ ~ ------777$77r ~ ------of 90% or more) C group SP o r m ore
Fig. 9. Construction of Sanyo Shinkansen
No.200 No.40
Unscreened gravel 1 . pit soil 2
/— Pit soil ■51 / /— Unscreened gravel 1, pit soil
Unscreened gravel R e ta in in g
Colloid 1 Clay | Silt | S an d G ra v e l
G ra in siz e Fig. 11. Section of Nobi Plain Banking Using Sand of Uniform Grain Size case of ordinary banking. However, in In practice, two or more of the above regions with horizontal and vertical cur methods were often used in combination. vatures, the permissible deviation is even For example, in the Kakegawa region there smaller, and this value must be halved. was weak ground consisting of peat to a depth of 5 m, and below it clay to a depth Therefore, the annual permissible amount of of 14 m. In this region, Shinkansen bank settlement has been taken as 100 mm in ing was performed in juxtaposition with the areas of straight track and 50 mm in areas banking of the existing Tokaido line. For with horizontal or vertical curvature. this purpose, sheet piles were inserted to These values, however, are only approximate block effects from the existing line and a standards. In actual calculations consid sand compaction pile was inserted in the eration is given to the allowance for error subsoil under the new banking. The bank in boring and consolidation tests, second unit with a height of 5.6 m in the form of ary consolidation, etc. Appropriate meas a counterweight fill was made by the step- ures are to be taken in construction by-step gradual embankment method. The methods so that the calculated values can total amount of settlement on the bottom be kept within one half of the numerical of the new bank was 1.4 m and the settlement values given above. of the shoulder of the existing line em bankment which makes contact with the new In consideration of structures built on bank was about 17 cm (Fig. 12). the roadbed such as electric poles, the target for the amount of residual settle In the Noba region an embankment was con ment which continues after opening of the structed to a height of 8 m on very soft line has been set at a maximum value of peat deposits about 7 m deep and 200 m in 50 cm in 10 years. In principle, banking total length. The method used was step- is not to be used in places where the by-step gradual embankment, but when the total amount of settlement from the start height of the embankment reached 2.5 m,a of banking exceeds 2 m, in consideration base failure occurred. Therefore, coun of the relation with structures on the terweight fills of 22 m in width were roadbed. prepared on both sides of the main bank. Sheet piles were placed between the main The following methods have been used for bank and counterweight fills as shown in banking of weak ground along the Shinkansen. Fig. 13. These sheet piles were connected This banking has been performed in 21 places by tie rods and the embankment was com and has a total length of about 7 km. pleted . a) Step-by-step gradual embankment The total amount of settlement reached 2 m at the bottom center of the embankment, and b) Counterweight fill because continuous settlement to the ex tent of 10 cm a year occurred after open c) Sand mat ing, it was necessary for several years to perform track raising by ballast filling. d) Sand drain 5-4 Viaducts on Weak Ground e) Sand compaction pile (1) Types of foundation used f) Preloading The foundations of viaducts and bridges on g) Replacement of shallow soft ground weak ground are of the following types depending on the subsoil and construction h) Driving of sheet piles or H-section conditions: piles at toes of slopes a) Precast reinforced concrete pile foun i) Change of design to bridge or viaduct dations (reinforced concrete piles, pre stressed reinforced concrete piles)
Fig. 12. Section of Banking of Weak Ground in Kakegawa Region b) Small diameter cast-in-place concrete pile foundations (cored piles, pedestal (3) Examples of viaducts on weak ground piles) (a) Example of deep weak ground and a deep c) Large diameter cast-in-place concrete foundation (Yanagisawa Bridge near pile foundations (Benoto piles, earth drill Numazu) piles, reverse circulation drill piles) As shown in Fig. 14, the Yanagisawa Bridge d) "Shinso" foundations (a kind of cast-in- crosses a valley with a width of about place pile foundation) 500 m. The tuff breccia which forms the foundation makes a deep drowned valley. e) Steel pipe pile foundations The depth of diluvial deposit is about 45 m. The surface strata are 15-20 m thick f) Open caisson foundations and consist of peat with clay below it. Standard penetration tests showed that the N- g) Pneumatic caisson foundations. value of each layer is 0 to 2 and there is artesian ground water in the gravel strata Among these different types, the precast at the bottom. In the plan originally reinforced concrete pile foundations are proposed, the settlement of the banking most commonly used. The various types of was calculated as 7 to 12 m and it was cast-in-place concrete pile foundations decided that economical and reliable bank are also often used under special condi ing would not be possible. Therefore, the tions such as in urban areas, in construc design was changed to a bridge. tion near structures and in cases of uneven bearing strata depth. Steel pipe pile From the results of a comparative investi foundations are used when the bearing gation of various types of foundation for strata are deep; the maximum depth in such the bridge such as the caisson, large- cases is 57 m. diameter cast-in-place reinforced concrete pile and steel pipe pile as shown in Table Caisson foundations are used mainly for 6, the steel pipe pile foundation as shown large bridges. Battered piles are also in Fig. 15 was adopted from the standpoints used in cases where the surface strata are of reliability and economy. The bridge is especially weak. Other methods include placed 12 m above the ground and it is replacement of subsoil in the surface in a section of curved track with a radius strata with good-quality gravel and soil of 2,500 m. Therefore, a large horizontal and increase of the horizontal resistance force acts on the piers because of the by means of rigid underground beams between centrifugal force of trains. The surface the footings. stratum of the subsoil consists of peat, and from a horizontal load test on the (2) Problems in structural foundations on piles, the horizontal subsoil reaction weak ground coefficient was found to be only k = ap proximately 0.4 kg/cm3. It was evident The following problems have arisen concern that no horizontal resistance could be ing structural foundations on weak ground. expected in the soil. Therefore, the steel pipe piles were inclined by 10° to (a) The question of the depth of the foun obtain horizontal force by means of bat dation, i.e. whether to use a deep founda tered piles. tion or a floating foundation, when the weak alluvial deposits are very thick and the bearing strata very deep. Bridge length: 511.92m (b) Foundation type and method of construc Span: 20-25m tion in the case of deep foundations.
(c) Selection of the type of foundation in cases of insufficient bearing strata.
(d) Foundation type and method of construc tion in cases where the basement strata under the weak ground are strongly inclined.
(e) Countermeasures and the use of battered piles in cases of insufficient horizontal resistance.
(f) Differential sinking between structures or between structures and banking structures.
(g) Type of abutment structure. Table 6. Comparison of Problem Points (b) Example of insufficient bearing strata for Various Types of Foundations and a foundation supported by these in the Yanagisawa Bridge strata (Viaduct in Nobi Plain)
Type of Fig. 16 shows a model of the Nobi Plain Characteristics and problems foundation subsoil. The top part is a weak superfi Construction costs are com cial deposit of a river background swamp paratively low. consisting of clay, peat, fine sand, etc. The intermediate sand stratum has N-values Horizontal resistance of upper of 10 to 20 and a thickness of 5 to 10 m. Well peat stratum presents a problem. Below this is a comparatively uniform There are many difficult prob marine clay deposit with N-values of 5 or lems concerning abnormal less. Under this is a rather solid stra settlement during construction tum of sandy soil and then a gravel stra and the handling of artesian tum with N-values of 50 or more. The groundwater at the bottom. depth of the gravel stratum which forms a sufficient bearing stratum is about 30 m. There is a time problem with respect to the number of As shown in Fig. 16, three types, A, B and machines. The horizontal C, can be considered as the depth of the Benoto resistance of the ground, viaduct foundation piles. The results of piles control of artesian ground loading tests on the experimental piles in water, etc., present problems various regions have shown that with A- in design and construction type foundation piles (diameter: 30 to work. 40 cm) which are 10 to 20 m long and have the tip of the pile in the intermediate The correct execution of the sand stratum,there are several regions cast-in-place concrete and the placing of reinforcements Pedestal presents a problem. piles Upper clay stratum There is also the problem of the indirect effects on exist River flood plain deposit ing piles at the time of cast ing . Delta or littoral deposit These are rather expensive but Steel construction of battered piles piles is easy and there are few Bay deposit design or work problems.
Reinforced These piles contain three concrete joined parts. Erection of Littoral-» fluvial piles battered piles is difficult. d ep o sit Fluvial gravel stratum There is a problem of future Diluvial deposit N>50 settlement caused by the drop Floating in groundwater pressure, etc. Fig. 16. Alluvial Deposits and Insertion foundation The construction costs are Depth of Pile Foundations in high for a completely floating Nobi Plain foundation.
Side elevation Front elevation, Foundation pile Detail of the head of steel pipe piles track center interval arrangement R . L . 1 6 0 0 r P 3 0 1 6 x 3 0 0 8400 r P 2
r P 0 1 6 x 4 0 0
1 Plan . 0 2 2 x 9 2 0
0 1 3 x 3 1 0 D iam eter Steel pipe 508mm
I j l Pï 022x920
thickness P 2 0 1 6 x 4 0 0 0
-P 3 0 1 6 x 3 0 0
Fig. 15. General Drawing of Yanagisawa Bridge Pier Foundation stringent standards of Shinkansen con struction which make it impossible to tion was beset by problems, such as great execution of a roundabout drift for (1) Outline (1) of Shinkansen tunnels avoid entirely areas of poor geology, quantities of spring water necessitating Further, in view of the varied and weak nature of the geology of Japan and the much of the Shinkansen tunnel construc land wasland avoided wherever possible because loose loose and there was not sufficient bearing tunnels, safe and reliablethe bottom method drift and for upper excavating • large tunnel is comparatively short. The lower level. Table 8 shows the excavation auxiliary methods such as inclined or foundations were used for rather long via for this are that about 70% of Japan is the Shinkansen were rigorous, and urban half-section cutting method which in the ployed where there are few joints in the rock and the natural ground is compara tively good. The open used cutting if the method tunnel is is located at a shal The bottom drift and upper half-section cutting method was used in the majority of cases. In long tunnels of km 5 or more, vertical shafts are often used. to to the difference of the negative skin friction. If the viaduct is supported by tlement between the viaduct and the adja fore, the deep end-bearing pile is not strength, shallow intermediate bearing pile 5-5 Shinkansen Tunnels There are many occurrences of spring water during tunnel excavation. Therefore, as a drift method is employed where the soil is upper half-section advancing method is used where the geology is good and the drift is first excavated to examine the geology and to control spring water is cent embankment becomes greater. There the intermediate sand layer was thin or ducts in the Nobi Plain. mountainous, construction standards for of the high land prices and for environ of Japan is full of variety and weak. is widely used in Japan 18). (Fig. The side of swelling type and the natural ground bearing strength is insufficient. The mushroom-shaped excavation method is em methods used for the Shinkansen tunnels. negative skin friction acts on the piles, and when this is considered as a load, it differential settlement among the piles due end-bearing piles, the difference of set always the best or the safest. Except when The number of tunnels used in the Shin kansen is relatively large and there are mental protection. As was described previously, the geology becomes very uneconomical. bearing piles, Even with there end- is the possibility of many tunnels 10 km or longer. The reasons values are the same. of alluvial Because of deposit settlement subsoil, rather high Section C—C Section D -D by by Underground Beams Fig. Fig. 17. Rigid Frame Viaduct Connected It It is doubtful if execution can be con for for ease and accuracy of construction, safe at first glance, but the following accuracy of execution is questionable. trolled so that all of the end-bearing former was found to be better not only from the standpoint of economy but also etc. Use of the end-bearing pile seems problems arise. When used, precast the piles piles must are have joints and ferences in subgrade reactions against the legs of each unit. frame type of viaduct is the most economi small small amount of overall settlement as not tages and disadvantages of a shorter pile the the structure is able to withstand slight cal cal but there should be no relative dif ferences in the settlement between the footings. For this purpose the footings to to disturb track maintenance. This is therefore, therefore, short foundation piles sup tions involves permitting only such a pile which reaches the gravel strata, the as as their foundations are of the same type. These decisions were made from soil tests and geological considerations. The rigid and and almost no differential settlement tively uniform, subsidence due to consoli differential settlement due to the dif ground rigid beams as shown in Fig. 17,and to to 80 t can be obtained. In these regions, bearing strata and a long-type end-bearing When consideration was given to the advan harmful to structures will occur as long dation is uniform over a fairly large area because the lower clay stratum is compara ported in the intermediate sand stratum were used. The design policy used for viaduct founda with the end resting in the intermediate were interconnected by means of under where an ultimate bearing capacity of 50 00601 drainage; weak areas with much water requiring setting of well points within the tunnel; crushed fault zones requiring combined use of pipe roofing; etc. The main problems are summarized in Table 9. As examples, two of the Shinkansen tun nels are discussed in outline below: the Shin-Kanmon Tunnel (18.713 km in length), which is the longest of those already opened, and the Seikan Tunnel (53.850 km in length), the longest of those now under construction.
A: Bottom drift and upper half-section cutting meth o d B: Side drift and upper half-section cuttinR method C: Upper half-section advanced method D: "Mushroom - shaped drift N ote: Numbers (1). (2)...... indicate sequence of operations
Fig. 18. Outline of Tunneling Methods Used in Japan
Table 7. Excavation Methods Used in Shinkansen Tunnels
Okayama-Hakata Excavation method Symbol Tokyo - Shin-Osaka Shin-Osaka - Okayama % of total length % of total length % of total length km % km % km % Bottom drift and upper half-section cutting A 45.4 (68) 47.8 (84) 158.9 (71) method
Side drift and upper half-section cutting B 7.2 (11) 4.1 (7) 17.6 (8) method
Upper half-section 9.6 advanced method C (15) 0 (0) 39.2 (17)
Mushroom-shaped drift D 2.0 (3) 1.6 (3) 2.1 (1)
Open cut method E 2.2 (3) 0.5 (1) 3.4 (2)
Shield driving method F 0 (0) 3.0 (5) 1.3 (1)
Total 66.4 (100) 57.0 (100) 222.5 (100) Table 8. Construction Methods for Long Tunnels (Length: 5 km or more)
No. of Construction Length aux. Area Name Geology method (m) piles Nangoyama 5,170 Tuff, andesite Bottom drift 0 Tokyo - Shin-Osaka
Tanna 7,959 Tuff, andesite, basalt, 11 0 II sulfotanic clay
Otowayama 5,045 Slate, chert II 0 It
Rokko 16,220 Rokko granite Bottom drift 6 Shin-Osaka-Okayama
Kobe 7,961 Nunobiki granite II 3 tt
Hosaka 7,575 Rhyolite II 0 II
Bingo 8,900 Rhyolite, granite Bottom and 2 Okayama - Hakata side drifts
Takehara 5,305 Granodiorite Upper half 2 II
Aki 13,030 Granite Bottom and 3 tl side drifts, "Mushroom"
Koi 5,960 " Bottom drift 2 II
Itsukaichi 6,585 " Bottom drift, 1 II upper half
Ono 5,389 It Bottom drift 0 II
Iwakuni 5,132 Slate, chert tl 0 tl
Shinkin-Meij i 6,822 Slate Side drift, 1 II upper half, bottom drift
Tomita 5,543 Granite, black schist Bottom drift, 0 tl upper half
Ohirayama 6 , 640 tl II Bottom drift 0 II
Shin-Kanmon 18,713 Sandstone, slate, Bottom and 9 tl granodiorite, etc. side drifts
Kita-Kyushu 11,747 Sandstone, slate, Bottom drift, 4 II shale, etc. full face
Fukuoka 8,488 Green schist, Bottom drift 1 tt granodiorite Outline of construction method construction of Outline with with (Details described in text.) in described (Details Pipes of 85 mm dia. and 30 m length were were m length 30 and dia. mm of 85 Pipes Pipes of 114 mm dia. and 35 m length were were m length 35 and dia. mm 114 of Pipes tunnel. were m 3,000 approx. of drifts roundabout sheets. tunnels (total: m). (total: tunnels 14,000 placed on the outside of the steel supports in in supports steel the of outside the on placed of lining completion after and holes, bored placed in bored holes. holes. bored surrounding the in grouted After placed were pipes the of inside the and ground main the from m distant 12 sides right and the of sides left and right on constructed these results, the temporary upper-half whole whole upper-half temporary the results, allow these sectional with constructed was lining curvature. tally and invert large were grouted with cement paste. cement with grouted were overcome was ground natural the of by Loosening increased was strength bearing ground and immediately then supports, steel H 250 using with water-glass type chemicals, excavation excavation chemicals, type water-glass with section. small of divisions in out carried was top tunnel main the from set were points to Well lowered was level water the and heading, level. formation tunnel the below top tunnel main the in set were points left Well the at tunnels pilot the in and heading zone, fault crushed m 1,200 the penetrate To bypass the from executed were borings age and used to predict settlement. settlement. on predict Based to used and driving in Lance sheets and by excavating excavating by and sheets Lance in driving Bernold using lining first out carrying ances of 60 cm vertically and 40 cm horizon cm 40 and vertically cm of 60 ances main tunnel, and 210 large-diaraeter drain large-diaraeter 210 and tunnel, main A center bottom heading was completed first first completed was heading bottom A center zone beneath seabed beneath zone Reason for adopting spe adopting for Reason method construction cial structures aboveground aboveground structures liguifaction and boiling. and liguifaction To reduce effects on on effects reduce To cover. earth thin to due fault crushed overcome To roadside and road trunk Since tunnel excavation excavation tunnel Since spring by flow soil extremely of zone fault 150 m below the tunnel. the below m 150 ing settlement or defor or settlement ing 2 0 kg/cm2. 0 2 Since tunnel excavation excavation tunnel Since To prevent settlement due due settlement prevent To an of presence the to 70- mine coal abandoned To To pass beneath m a 5-10 allowing drive-in, caus without cover earth was impossible due to to due impossible was water. crushed a penetrate To mation . mation was impossible due to to due impossible was weathered granite with with granite weathered water pressure under under pressure water Combined Use of Special Auxiliary Methods Auxiliary Special of Use Combined l/sec.; Table 9. Examples of Shinkansen Tunnel Construction Tunnel 9. Table Shinkansen of Examples (Geology; Execution length) Execution (Geology; (Tuff, andesite; 600 m) 600 andesite; (Tuff, (Weathered tuff, shale, clayey clayey shale, tuff, (Weathered (Sanyo) gravel, of layers (Alternate (Extremely fine sand with water, water, with sand fine (Extremely (Alternate layers of sandstone sandstone of layers (Alternate (Silt with sand and gravel, gravel, and sand with (Silt (Crushed zone of extremely extremely of zone (Crushed 300 m) 300 Shin-Kanmon (Sanyo) Shin-Kanmon m 880 of m 35 zone; crushed spring water of 800 800 of water spring reclaimed land; m) 100 land; reclaimed Name of tunnel (Shinkansen line) line) (Shinkansen tunnel of Name undersea section) undersea sand, silt, clay, etc.; 700 m) 700 etc.; clay, silt, sand, Uegahara section of Rokko tunnel tunnel Rokko of section Uegahara Tsurukabuto section of Rokko Rokko of section Tsurukabuto (Sanyo) tunnel and shale; 1,000 m) 1,000 shale; and Muroki Muroki (Sanyo) Noguchi tunnel (Sanyo) tunnel Noguchi weathered granite; 1,200 m) 1,200 granite; weathered method Construction Pipe roofingPipe 1 No. (Tokaido) Atami for drainage for lining with with lining invert system Roundabout drift drift Roundabout full-section full-section Well pointWell Obara (Tokaido) Simultaneous Simultaneous Lance-Bernold
253 (2) Outline of the Shin-Kanmon tunnel fault zone 300 m in length from the piedmont of Hinoyama to the undersea sec (a) Basic plan tion, faults near the piedmonts of Tani- machi and Togamiyama and Tomino, etc. These The Shin-Kanmon tunnel is a double-track zones account for 23% of the total length. undersea tunnel for the Shinkansen under Among these areas, breaking through the the Kanmon Straits. Its 18.713 km length crushed fault zone in the undersea section ranks third in the world after the Simplon was the key to the success or failure of Tunnels (parallel single-track types, the project. 19.823 km and 20.036 km) between Switzer land and Italy. The design thickness of the concrete lining of the tunnel was of two basic types: 50 The Shin-Kanmon tunnel project had the cm and 70 cm. In cases where the geology following characteristics: (1) very care was especially bad, a special sectional ful consideration had to be given to the shape was used. Table 10 shows the stand route location because of the severe Shin ard thicknesses of the lining for each type kansen standards with respect to track of rock. curvature and grade, etc.; (2) since the tunnel was very long and located under the To complete this tunnel in 4 years, the sea, it was decisive in determining when total length was divided into seven work the Sanyo Shinkansen to Hakata would open; sections, each of about 3 km. Studies and (3) special care had to be given to were made on ground conditions, geology, the execution plan, the execution of the etc., for installation of the inclined and undersea section and that in urban areas vertical shafts. As a result, one vertical where tunnels are located at a shallow shaft and six inclined shafts were provided. level. Work sections of 2 to 3 km in length were selected as being both economical and ra The project was commenced in both Kyushu tional . and Honshu in August-September 1970. After many difficulties had been overcome, The standard excavation method was the the main tunnel was completed by the end bottom heading and upper half-section cut of June 1974. Then came the track and ting method, which is readily convertible electrical work and the first test-run to other methods and which permits confir train through the tunnel on October 25, mation of the geology and spring water by 1974. means of the drift. Other methods were used as required by the geology and other For the location of the route, the follow conditions. ing points were taken into consideration: The following sections give an outline of (i) The undersea section should be as the execution in the crushed fault zone in short as possible. the undersea section which was the key to the success or failure of this project. (ii) Existing urban areas should be avoid ed as far as possible.
(iii) Near both ends of the tunnel, Shin I HONSHU 1 kansen stations would connect with the existing Sanyo and Kagoshima Lines.
(iv) The crushed fault zone should be avoided where possible in the undersea section.
(v) There should be sufficient overburden Kujigatani wherever possible in the undersea section. Hinoyama Kanmon Bridge Kanmon road (vi) Provision of the intermediate working drift should be easily accommodated. V ------Shinkansen The route was decided as shown in Fig. 19. Shinkansen Fig. 20 shows the geology of the area near ~ ™ Conventional the tunnel.
The regions with poor geology included a clay and weathered loose rock zone for about 1,000 m from the Shimonoseki mouth of the tunnel; a 900 m long region of weathered granite with much spring water in the Fujimatsu area; and a diluvial plateau and an area of clayey slate 1,000 m in length near Tomino vertical shaft; as well as several faults running through the basin near Mukuno, a crushed Table 10. Tunnel Design Standards
Type of rock I II III IV
Hard 3.0 or less 3.0 - 3.8 3.8 - 4.5 4.5 or more Seismic rock wave Loose velocity 2.0 or less 2.0 - 3.0 3.0 - 3.8 3.8 or more rock
Thickness of 70 70 50 50 tunnel lining (cm)
150 H,1.5 m pitch spray application 200 H-type steel 200 H-type steel 175 H-type steel of concrete Upper half arched timbering temporary support 1.0 m pitch 1.35 m pitch (shot-crete) 0.9 m pitch 10 cm rock bolt 0 22 m m , I 2 m , 1.2-1.5 m pitch
E3 Talus and alluvial deposit I ■ --j Sedimentary rock (tertiary) " (mesozoic)
llllilll * (paleozoic) r m Porphyry
Granite and franodiorite
Fault and crushed earth rone
[ 1 Weathered zone
Fig. 20. Profile and Geological Map of the Shin-Kanmon Tunnel (b) Execution near the main fault zone in faults of 5-10 m in width in the middle of the undersea section the straits. There was much spring water but the rest was hardened. The spring (i) Outline water in the undersea section was mainly concentrated in an area extending 80 m Among the methods for execution of the from the coastline on the Honshu side. In undersea section, the pneumatic shield addition, there was also much spring water driving, trench and freezing methods were near the Kyushu side of the main fault and available. However, in view of the facts near the center of the straits. The flow that (1) the water pressure was about 7 rate of spring water in the undersea sec kg/cm2, (2) the crushed zone and rock bed tion was 8 tons/min. coexist, (3) ship passage is frequent and the tidal current is fast and (4) the (ii) Execution near the main fault freezing point of seawater is low, it was decided to use the ordinary tunnelling From the results of execution of the sur method by cutting off and strengthening vey tunnel, etc., execution in the main the ground using grouting. fault to about 100 m from the coastline on the Kyushu side consisted of pipe roofing, From the inclined shaft to a place about groundwater cut-off and strengthening by 20 m from the coastline on the Honshu side, chemical grouting, dividing into small the geology of the undersea section showed sections and excavation while lining with alternate layers of rhyolite tuff and concrete. rhyolite which had undergone weathering and thermal metamorphosis. There were many Fig. 22 gives an outline of the execution fissures and large quantities of spring method. First, pipes 35 m long, 114 m in water. For the next 80 m from the coast diameter and 5.25 mm thick were pushed in line, the rock structure consisted of shale around the excavated part as shown in the and rhyolite tuff and porphyrite with much figure at a position about 5 m in front of spring water. Between 80 and 115 m from the fault. Via this pipe, natural ground the coastline, there was the largest crushed was grouted around the pipe and water- fault zone (hereafter referred to as the glass type chemicals inside it. Water main fault) in the undersea section (Fig. cut-off and strengthening were performed. 21) and special methods were used for the The grouting consisted of water-glass type survey and main tunnels. This fault con chemicals inside the excavation section sisted of a clayey crushed zone about and within a range of about 3 m outside 20 m wide including fault breccia, 20-30 the excavation section of the lower part from cm clay seams sandwiching this crushed the spring line, and of urea resin within zone and a disturbed zone of several me a range of 8 m outside the excavation sec ters on the outside. The 115 to 200 m of tion of the upper part from the spring line. the main fault on the Kyushu side consist To improve work efficiency, pipe insertion ed mainly of sandstone which had undergone and grouting were performed from both the thermal metamorphosis and, especially in Honshu and Kyushu sides toward the main the 140 to 160 m region including small- fault. scale faults, there was crushing and large quantities of spring water. Beyond this After completion of the lower stage of point on the Kyushu side, the composition grouting, excavation of the main fault was was entirely of granodiorite with several performed in parallel with the upper pipe
porphyrite L (heavily K h yo litic , A; t»ff V -shale / |,»uIt & :'tu ffV j'£ weathered i Af(heavily ' ( heavily / fracture leathered) M *'weathered") weathered) z o n e ^ > - fractui •Sandstone ’ • I +/ (many cracks) /+. | ip i '\ / - ( w eathered)^% ‘^ J r / p V » l-au . • • ' Grano m c la y ' T u ff . d io rit weathered) fi» ¿fi'LZU ^Shalej- ^J ircular. 'Standar3+| (weathered) section *, section- | j— •/+ I Shin-Osaka I're-boring chamber 11m 1 To Hakata ‘ I’re-lMirinj! fjTj Bottom d rift roofint; (side drifts) 351 •chamber 11m i~*
reathered) insertion. First, the total region of railway transportation is linked to Hok about 35 m of first-stage side drift (2) kaido by the 113 km Japanese National Rail on the right and left sides from the Hon ways ferry routes between Aomori and shu side was excavated and immediately the Hakodate. The fleet consists of 13 section was filled with concrete (3) . Then passenger and cargo vessels which make as the same procedures were performed in turn many as 30 round trips a day in the peak up to the fourth stage @ , @ • After the season. In fiscal 1975 these ships carried concrete filling and before excavation of 4,320,000 passengers and 6,060,000 tons of the next side drift, auxiliary grouting cargo. was performed, the natural ground was re strengthened and water cut-off was per The ferryboat passage between Aomori and formed. After completion of execution of Hakodate requires a net navigation time of the 4th stage side drift, grouting was 3 hours and 50 minutes, or a total of 4 performed again in the upper half. Then hours and 20 minutes including the train the upper half @ was excavated by the changing time. Therefore, the trip from ring-cut method. H-type steel arched Tokyo to Sapporo takes 16 hours and 50 timberings were placed at 60 cm intervals minutes by limited express train. and concrete was placed between them using Bernold sheets. Then the first lining The Aomori-Hakodate service is limited by concrete (D) was poured 5-6 m behind the wharf conditions to 30 runs and it is dif temporary lining concrete. After excava ficult to cope with increases in traffic tion of the ring part and the first lining demand. Because of severe weather, several concrete had been completed in this way, hundred voyages have to be cancelled every the central part (O) above the spring line year and there have been accidents in the was excavated, the support pipes on the past including one sinking (death toll: inside of the 3rd and 4th stage side drifts 1,414) . were removed, and the excess portion of the first concrete lining which was ob It is estimated that the railway traffic structive to the second lining was removed. volume between Aomori and Hakodate will Next, the lower half (fi) and invert (0) were reach 18 million passengers and 20 million excavated and all of the first and second tons of freight annually in the future. stage supports, pipes, and excess first Under such conditions, the Seikan tunnel concrete lining were removed. The work was has become the major means to relieve done in sections of 3 to 5 m and invert @ transport capacity deficiencies. was installed. Then the second lining con crete @ was poured and the main work on To assure adequate transport, it is planned the section was completed on May 31, 1974. to excavate a Shinkansen-type tunnel which will make possible a direct Shin- (3) Outline of the Seikan tunnel kansen link between Honshu and Hokkaido. When completed this tunnel will make it (a) Outline (Fig. 23) possible to cover the 1,100 km between Tokyo and Sapporo in 5 hours and 40 min The Tsugaru Straits which separate the main utes which will be of great benefit to the Japanese island of Honshu from Hokkaido are public. Currently, all of Japan's tunnel subject to severe weather conditions and ling technology is being concentrated on navigational difficulties and connecting the Seikan Tunnel. traffic is often disturbed. At present, Despite the fact that there is still about 13 km of unknown seabed, the future chal-
15.25 mm PROCEDURE
Fig. 22. Execution of the Tunnel Through the Fault Zone Under the Straits lenge is that there must be no accidents breccia tuff, ordinary tuff and silty rock under the special undersea tunnel condi known as Kunnui stratum. Except for the tions of high-pressure spring water and crushed fault zone, there are few cracks complex geology. Further technical devel and little spring water and the geology is opment is now under way to assure greater comparatively stable. The geology of the safety and speed. land part on the Hokkaido side begins with a short continuation of the Kunnui stratum, There will also be many technical problems followed by a gradual shift to the Yakumo in equipping the completed Seikan tunnel and Kuromatsunai strata in the middle of in relation to train operation safety, the straits (Fig. 24). maintenance, ventilation and emergency measures. These problems are currently It is estimated that there is a consider under investigation. able amount of spring water, which is most likely to cause disturbances in undersea (b) Outline of geology tunnel excavations, in the fissures between the andesite and intrusive basalt on the The geology of the undersea section of the Honshu side, the nine rather marked crushed route of the Seikan tunnel consists of fault zones and the affected areas adjacent volcanic, pyroclastic and sedimentary to these zones. rock belonging to the tertiary miocene period. One-third of the part on the (c) Work plan Honshu side consists mainly of andesite and tuff breccia. There are also several Since the route of the Seikan tunnel is to intrusions of basalt and rhyolite. Rock be such that there are as few dikes as characteristics are complex with many possible in the volcanic region on the cracks. The land part on the Honshu side Honshu side, the length of the undersea shows almost the same tendencies. One- section will be 23.3 km and the approach third of the central part of this strait grades on both ends will be 12/1,000 so consists mainly of hard shale and silty that the Shinkansen trains can enter the rock known as Yakumo stratum and sedimen tunnel at a speed of 250 km/h and a speed tary rock made up of silty rock and fine of 170 km/h can be assured even in the sandstone known as the Kuromatsunai stra region of continuous upward grade on the tum. The latter is soft and is the most exit side. As a result of the minimum recent formation. One-third on the overburden of the undersea section being Hokkaido side consists mainly of volcanic set at 100 m, a tunnel of 53.85 km is
(a) Plane Geological Map
Tsugaru Matsumae Peninsula Peninsula Seikan tunnel £=53k850m00 OkOOOmOO' Tsugaru Strait Seikan tunnel 53k 850m 00 400m (b) Profile Geological Map 200
0
200 ;Main tunnel •Working drift 400 5 10 15 20 25 30 35 50km Honshu section Undersea section Hokkaido section I [Alluvial deposit : . .JSetana stratum I I Alluvial deposit I v » IC en o zo ic a n d e s ite E S I Kuromatsunai stratum I j v f Cenozoic andesite I l l IR h v o lite Yakumo stratum l-I-I-1 Kuromatsunai stratum ^==|Kodomari stratum I a a i B a sa lt F=— I Yakumo stratum iv v I Paleozoic (Tappi) I v v IPaleozoic andesite (SSJKunnui stratum a n d e site l**vJStrata boundaries r a [Area with many of th< | a a lArea with many of same rocks as above H^Y oshioka stratum F = i F a u lt the same rocks as a b o v e f/w 'IKunnui stratum U ¿IFukuvama stratum IH M Syncline I* * IFukuvama stratum IbaSaPaleozoic stratum I I Anticline currently planned (Fig. 24). This minimum for detailed survey of the geology and overburden of 100 m was decided on the collection of data relevant to the selec basis of experience gained in the excava tion of execution methods, etc. Since it tion of undersea coal tunnels, etc. will serve also as a drainage tunnel via an inclined shaft to drain any spring water Two proposals were investigated for the from the main tunnel after completion, it tunnel sectional shape: one double-track will be excavated in the lowest position. tunnel or two single-track tunnels. The former type was chosen since Construction of the working drift will be while the air resistance during train advanced prior to the main tunnel for operation will be much lower, excavation geological surveys at the main tunnel level is only slightly more difficult than in and advance control of spring water. By the latter type. The sectional shape will providing the working drift with branch be a horseshoe shape in the normal geology drifts, it will be possible to increase the zones, and in zones where the geology is number of locations for the main tunnel especially bad it will be as near to circu excavation. Thus, the working drift will lar as possible. play the same role as the driftway in ordinary tunnels. In principle, a concrete lining 70 cm thick will be used. Increased lining thicknesses Both the pilot tunnel and working drift in accordance with earth pressure have been are intended to shorten the work period for considered. As in ordinary tunnels, drain the tunnel excavation as a whole, and since holes will be provided so that spring water progress must be as fast as possible, ex will be released from the rear and as lit cavation by TBM in zones of good geology is tle water pressure as possible will be being considered. Shot-crete will be used applied. In cases where water cut-off is as the lining method. particularly necessary, water cut-off zones will be provided by grouting with respect (d) Current state of the work and future to the natural ground around the tunnel. technical problems After the lining is completed, backfill grouting will be performed over the entire Since the Seikan tunnel was started in May circumference. For execution of the main 1964, it has been possible through various Shinkansen double-track tunnel, a small types of surveys to get a broad perspec pilot tunnel and working drift will be tive of the distribution of geological excavated (Fig. 25). The pilot tunnel will strata and rock and the location and scale precede the main tunnel and working drift of folding and crushed fault zones. As of the end of January 1977, a total of 46,655 m including 10,030 m of pilot tunnel, 10,035 m Standard section of working drift and 26,590 m of main tunnel (in m eters) (3,615 m of the Honshu approach, 12,275 m of the undersea section and 10,700 m of the Hokkaido approach) have been excavated after solution of the various technical problems involved. These completed parts have passed through the volcanic region on the Honshu side, which has much spring water, three of the nine distinct crushed fault zones, and the soft rock strata on the Hokkaido side (Fig. 24).
To complete the most difficult central undersea section more safely, quickly and cheaply in the future, it will be necessary to develop high-level techniques for: de tailed prediction of geological conditions, water cut-off and grouting for high pres sure and treatment for unlimited spring water, use of high-speed excavation to shorten working time, use of shot-crete Inclined shaft for fast and economical lining and salt- Vertical shaft water-resistant lining for greater endur Tappi side Yoshioka side ance, treatment of leakage and drainage, ventilation, etc. The main techniques are described in the following sections.
(i) Pre-boring
The water pressure acting at the tunnel level is 24 to 28 kg/cm2, almost equal to the head from the seawater surface. Since the source of water is unlimited, unex pected outflows can cause fatal disaster. In the Seikan tunnel the working drifts are (iv) Shot-crete provided with side sockets from which hori zontal pre-borings are performed for a Until recently, mainly the dry shot-crete length of 400 to 800 m. As of January 1977, method was used in the Seikan tunnel, but 90 holes of 33,524 m in total length had the wet shot-crete method is being employed been completed. The boring becomes diffi increasingly because of such advantages as cult in the case of bad geology zones, because improved spraying capacity and less dust of spring water and the collapse of boring generation. holes. The pressure-drive method in which pressure is maintained in the holes and the (v) Drainage double-tube method in which casing pipes are inserted at the same time as driving In the Seikan tunnel, drainage equipment is are used to cope with the difficulty. In extremely important. The amounts of spring addition, attempts are being made to in water in the tunnel on the Honshu and crease the boring hole length by testing Hokkaido sides are currently 28 and 5 tons the electro-drill as a head-driving method. per minute respectively and are gradually In addition to pre-boring, several survey increasing as the tunnel becomes longer. bores are always made from the face loca The pumps to remove this water have capaci tion to assure safe excavation by confirm ties of 110 tons per minute on the Honshu ing the geological conditions in front of side and 94 tons per minute on the Hokkaido the face. side, allowing an adequate safety margin even during abnormal outflows. As the tunnel (ii) Grouting advances, it is planned to install pumps at intervals to prevent any future accident. In the Seikan tunnel, subsoil grouting tech niques play an important role, and various technical developments are being attempted to improve execution efficiency and to 6. CONCLUSION increase the grouted subsoil reliability. As described above, the most modern and In addition to cement grouting, water- high-level techniques have been used in the glass type chemicals are being used to construction and operation of the Shin- improve execution efficiency with respect kansen. In particular, geotechniques and to strength, solidifying time and viscosity. tunnelling engineering have played a major role in coping with the complex geological As of January 1977, 45,630 m 3 of cement and soil conditions of Japan. grouting and 23,430 m 3 of chemical grouting for a total of 69,060 m 3 had been completed. Since the Shinkansen was first opened in The minimum grouting pressure is 2 to 3 October 1964, it has been used by a total times the spring water pressure. of 1.1 billion passengers without a single accident involving bodily injury to pas (iii) Excavation sengers. In 1965, Shinkansen revenues accounted for 14% of all Japanese National In this tunnel, the upper half-section Railways passenger revenues and by 1975 advanced method and the bottom drift and this figure had risen to 36%, making a upper half-section inverted lining method major contribution to the railway budget. are used primarily. The side-pilot method and other divisional methods are also used The success of the Shinkansen in Japan has depending on geological conditions. shown that the supposedly declining rail ways have a new potential in high-speed For the pilot tunnel and working drift, the transport, thus affording suggestions to full-face method is used in principle and countries all over the world. the divisional method is also used where required by the geological conditions. It is my sincere hope that worldwide ad vances in research and development of tech In the future, attempts will be made to nology in all related fields, including improve excavation efficiency of the Seikan soil mechanics and foundation and tunnel tunnel by mixed use of ordinary blasting, engineering, will contribute to a variety machines such as load headers or TBM, of projects with the Shinkansen serving as depending on the circumstances. a model, and ultimately to improving the quality of life.