china tunnel waterproofing

7/29/2019 China Tunnel Waterproofing

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T U N N E L W A T E R P R O O F IN G M E T H O D S

T u n n e l W a t e r p r o o f i n g P r a c t ic e s in C h i n aY . Y u a n , X . J i a n g a n d C . F . L e eA b s t r a c t - - W a t e r i n gr e ~ s in t r a n s p o r t a t io n t u n n e l s n o t o n l y w i l l sh o r t e n t h e d u r a b i li t y o f c o n c re t e li n i n ga n d r e d uc e t h e f u n c t i o n o f e s t a b l is h m e n t s i n th e t u n n e l, b u t a ls o w i l l w o r s e n t he t u n n e l s u r r o u n d i n g s o m u c ht h a t t h e t ra f f i c w i l l b e g re a t l y a f f e ct e d . In t h i s s i t u a t i o n , t he ref ore , h i g h m a i n t e n a n c e c o s t s a re c o m p u l so ry .In m a n y c a se s, a p e r f e c t a p p e a ra n c e i s s t ro n g l y re c o m m e n d e d t o t a k e m e a su re s i n o rd e r t o p re v e n t l e a k a g e.H o w e v e r , i n C h i n a , t u n n e l w a t e rp ro o f r e q u i re m e n t s a n d s t a n d a rd s f o r v a r i o u s sp e c i a l u se s a re c o n s i d e ra b l yd i f f e re n t , su c h t h a t t h e b a s i s w h i c h e n g i n e e rs a p p l y t o d e s i g n i n w a t e r -c o n t ro l i s i n su f f i c ie n t . E sp e c i a l l y i nm o n t a n i c re g i o n , u n p l e a sa n t g e o l o g i c a l c o n d i t i o n c o n f i n e s e n g i n e e rs i n w o rk i n g o u t m o re re a so n a b l em e t h o d s t o s t o p w a t e r se e pa g e , e v e n le a k a g e . In t h i s p a p e r , t h e c u rre n t w a t e rp ro o f i n g re q u i re m e n t s a n dm e a su r e s i n d i f f e re n t spe c , a l t u n n e l s a d o p t e d i n C h i n a a re re v i e w e d . Th e l i m i t a t i o n s o f t h e p o p u l a r m e t h o d si n se v e ra l p ra c t i c a l c a se s a p p l i e d t o p re v e n t w a t e r l e a k a ge , su c h a s w a t e r t i g h t l i n in g , d r a i n a g e sy s t e m , a sw e l l a s g ro u t i n g , a re a n a l y ze d a t l e n g th . Th e n , so m e a v a i l a b l e m e a su re s , r e g a rd i n g c o n c re t e li n i n g ,w a t e r t i g h t l a ye r , d ra i n a g e e s t a b l i sh m e n t s a s w e l l a s c a s t i n g w a t e r t i g h t c o nc ret e, a re p ro p o se d , w h i c h w et h i n k i n d i sp e n sa b l e f o r t u n n e l e n g i n e e r i n g t o e f f i c ie n t l y c o n t ro l w a t e r se e p a g e a n d e v e n c o m p l e t e l y p re v e n tw a t e r l e a k ag e . In t h e e n d t o a n a l y ze t h e see p a g e f i e l d i n m o n t a n i c t u n n e l s , t h e f i n i t e e l e m e n t a n d b o u n d a rye l e m e n t c o u p l in g a n a l y s i s m e t h o d i s p r e s e n te d . A s a n e x a m p l e , t h e s e ep a g e f i e ld i n Z h e n w u s h a n t u n n e l o fC h o n g q i n g i s s i m u l a t e d . Th e c a l c u l a t i o n re su l t s c o i n c id e w i t h t h e i n - s i t u d a t a w e l l , a n d p ro v i d e c re d i b l ee v i d e n c e f o r t h e w a t e r p ro o f m e a su re s w h i c h w i l l be t a k e n i n t h a t t u n n e l p roj e c t . Th e m e t h o d p re se n t e d i n t h i sp a p e r w i l l sa v e e x p e n d i t u re s f o r su rv e y i n g m e a su re s a n d w i l l e n a b l e m o re re a so n a b l e a n d re l i a b l ew a t e rp ro o f i n g m e a s u re s ~.o b e t a k e n . 2000 Published by Elsevier Science Ltd. All rights r e s e r v e d .

I n t roduc t ion

W ater ingress :in undergro und works remains quitedifficult to assess. In man y tunnel s buil t long ago,seepage is unavoidable. Especially for tunnels infrozen zones, the tu nnel ground m ay be icy and the top of hetunnel so covered with hanging icicles that traffic is inter-rupted. Given this situation, high maintenance costs arecompulsory. For watA,~r supply tunne ls thro ugh sewagelayers and those furnished with wiring, a perfect appear-ance is usually strongly recommended to take measures inorder to prevent leakage.However, in China, tunnel waterproofing requirementsand standards for various special uses are considerablydifferent, a nd the basiis on which engineers apply water-control design is insvfficient. Especially in mountainousregions, poor geological conditions compel engineers to devisemore reasonable methods to step water seepage, and evenleakage. As a result, m any topics related to waterpr oofing --including the theoretical basis for water-control design, opti-mization of waterp roof measures, and rat ionality of tunnelwaterproof system--requ ire further investigation.

Present addresses: Yuan Y. Ryan, Professor and Deputy Dean ofthe Department of Buildi:ag Engineering, Tongji University, 1239Siping Road, Shanghai 200092, China; X. Jiang, Ph.D. candidate,Department of Building Engineering, Ton~i University, 1239Siping Road, Shanghai 200092, China; C. F. Lee, Professor andDean of the Department of Civil Engineering, The University ofHong Kong, Pokfulam l~bad, Hong Kong, China.

To treat underground water seepage reasonably andcomprehensively by means of drain age and prevention, it iscrucial for designers to unde rst and the dis tribution of un-derground seepage field and the potential permeable vol-ume at places excavated. During construction, the mostcritical zone is located at the tunne l face, where the decom-pression owing to excavation and water seepage forcesgenerated by the water flow toward the face can lead tocollapse of the face.Up to now, only a few papers have de alt with methods ofassessing the supporting pressure and seepage volume atthe tunn el face. Several of these methods have been basedon the plasticity principle. Davis et al. (1980) established ananalytical expression for cohesive and frictional soil inundrai ned conditions. Leca and Pane t (1988) have studiedthe more complex case of cohesive and frictional soil indrained conditions. Descoeudres and Rybisaial have re-viewed tunnel methods adopted in China.In this paper, the limitations of the popu lar methods inseveral practical cases applied to prevent water leakage,such as watertight lining, drainage systems, and grouting,are analyzed at length. Then some available measuresrelating to concrete lining, watertight layer, drainage es-tablishme nt, an d casting wate rtig ht concrete, are proposed.The authors consider these measures indispensable fortunnel engineering in order to efficiently control waterseepage or even completely prevent water leakage.In addition, based on Darcy's law and the Finite Eleme ntMethod along with Boundary Element Method, the three-dimensional nu merical simulati on is employed to model thedisturba nce of the initial hydraul ic conditions. That is, the

w w w , e l s e v ie r . c o m f l o c a t e / t u s t7hnneUing and Underground Spa~:e Technology,VoI. 15, No. 2, pp. 227-233, 20000886-7798/00/$ - s e e f r o n t m a t t e r 2000 Published by E l s e v i e r S c i e n c e Ltd.All rights r e s e r v e d .P I I : S0866-7798(00)00048-1

Pe r g amon


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F i g u r e 1. C o n s t r u c t i o n o f t h e Z h e n w u M o u n t a i n T u n n e l .

underground water level and hydraulic heads under orabove the potential tu nnel are adopte d to determ ine bound-ary conditions; then a three-dimensional finite elementanalysis model of st rat um seepage is established.In the last step of the res earch, a two-dimensional finiteelement equilibrium analysis for the Chongqing ZhenwushanTunnels is performed to find the largest permeable volumeand seepage forces around tun nel. Two kinds of cases aresimulated: namely, seepage water is (1) drained out or (2)stopped.The results of these analyses results have become theimportant theoretical basis for waterproofing measuresemployed in Zhenwushan Tunnel (Fig. 1). The longestportion of his tunne l is 2040 m long, and its elevation in theroadway surface is +352.4 m. The tunnel lies in the hillyregion in southeast of Chongqing, which belongs to thesubtropical zone and has a moist climate and abundantrainfall. The are a is full of unde rgro und rivers a nd pipeswith water for the whole year; the highest water level is+457 m high. A section profile is shown in Figure 2.2 . W a t e r p r o o f C r i t e ri a a n d T h e i r L i m i t a t io n s i nC h i n e s e T u n n e l E n g i n e e r i n g2.1 Wa terproof Criteria in Chinese T unnel Enginee ring

A general wat erpro of requ irem ent is stipulate d in '%Va-terproofCriterions in Underground Engineering" (GBJ108-87). This requirement stipulates that prevention, drainage,interception and caulking should be integrated in syntheti-cally controlling of water ingress in un derground engineer-ing. For various tun nel enginee ring works such as railway,highway and metro, a specific waterproof requirement andrank should be constituted according to the requirementson function and construction cost, as well as appearance.The general waterproof requirement is also set forth in"Design Criterions of Railway Tunnel" (TBJ3-85), "Con-struction Criterions of Railway Tunnel" (TBJ204-86) and"NATM Directory of Railway Tunnels". In addition, a com-plete preventive and dr ainag e syst em is required to achievea reliable and economical wate rproo f system.On the basis of general waterproofing requirements,surface water and undergr ound water are controlled in the"Technical Standa rd of Highw ay Engineering" (JTJ01-88).Reliable prevention and drainage measurements are re-quired for highways and A-class roads, in order to insure

safe transportation and a practicabledrainage fixture in tunnels. "DesignSpecification for Highway Tunnel"(JTJ026-90) sets forth special require-ments for A-road tunnels. This specifi-cation stipulates no water drops on thetop arch and latera l walls, no accumula-tion of wate r on the tun nel ground, andno seepage surrounding the equipmentholes. In addition, in frozen zones andduring the frozen period, there must beno accumulation water behind the tun-nel lining and no freezing water in thedrainage ditch.In the "Code for the Design of Metros"(GB50157-92), it is demanded that (1)no seepage occur in the sections tha t a refull of station s a nd equipment , an d (2)no moisture appears on the surface.Furthe r, no line-flow and no slurry- sandleakage should appear in other sectionsas well as in avera ge tunnel works. Oth-erwise, if a small quantity seepage ap-pears, its le aking capaci ty should be notmore th an 0.5L/m 2per day and night. Inaddition, some reinforcemen t should beemployed at such special parts as move-mentjoints, construction oints, and pre-established pipes. If only waterpro of concrete is employed ina corrosive medium, its anti-corrosion coefficient should notbe less than 0.8; otherwise, other reliable measures shouldbe taken.

2.2 Limitations of Chinese Tunnel W aterproof CriteriaIn most tunnel eng ineer ing, waterpro of ing m ethodsshould follow relative technical codes. Unfortunately, inChina these criteria have limitations.First, waterproofing categories are ambiguous. Com-pared with thos e in other countries, waterpro ofing require-ments and ranking methods are unclear. Since there is nospecific approach, it is very difficult for engineers to dealwith water ingress in design and construction practice

based on vague concepts such as 'allowable seepage' or'seepage prohibited'.Second, the definition of the wa terproofi ng standa rd isrelatively vague for different tunne l criteria. For example,except for a general waterproo fing specification, no detailedrequirements are established in the regime of railwaytunnels. Furthe rmore, an A-class waterproo fing design in arailway tunnel is by far different from that in a highwaytunnel.

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F i g u r e 2. S e c t i o n o f t h e Z h e n g w u s h a n T u n n e l .

228 TUNNELLINGAND UNDERGROUNDSPACETECHNOLOGY Volume 15, Numb er 2, 2000


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I IWaterproofing sys tem Waterproofing sys temw i t h ~ l , s e c o n d p r o t e c t i o n l a y e r w i t h s e c o n d p r o t e c t / o n l a ye r

Figure 3 . Com posi te l iin ing waterpr oof ing method.T h i r d , w a t e r p r o o f o p e r a t i o n i s u n s a t i s f a c t o r y . N e i t h e r ag e n e r a l w a t e r p r o o f i n g p r o v i si o n n o r s y s t e m a t i c r e s e a r c ho n w a t e r p r o o f o p e r a t i o n s w i t h r e s p e c t t o e c o n o m y a n de f f ic i e n cy h a s b e e n r e a l i z e d i n C h i n a . T h e s t a n d a r d o n

w a t e r p r o o f in g o p e r a t io n a n d m e a s u r e m e n t s i s p oo r ly co n -s t it u te d . B e c a u s e n o u n i fo r m a s s e s s m e n t s y s t e m i s e s ta b -l i s h ed , v a r i o u s w a t e r p r o o f i n g o p e r a t i o n s c a n b e c a r r i e dm a i n l y o n t h e b a s i s o : Fp r ac t ic a l e x p e r i e n c e w h i c h , t o s o m ee x t e n t , h a s b e e n p r o v e n u n s c i e n t i f i c b y t h e w a t e r l e a k a g et h a t h a s o c c u r r e d o n f i n i s h e d t u n n e l s .P r a c t ic a l l y , d a t a p r o v i d e d t o tu n n e l w a t e r p r o o f i n g d e -s i g n e r s i s i n su f f ic i e nl L B e c a u s e o f t h e c o m p l e x g e o l o g i c a lc o n d i t io n s a n d t h e h i g h c o s t s o f e n g i n e e r i n g i n v e s t i g a t i o n ,i t is d i f fi c u lt t o c o m p l e t e l y m a s t e r i n f o r m a t i o n a b o u t u n d e r -g r o u n d w a t e r a r o u n d t u n n e l s . C o n s e q u e n t l y , t h e a u t h o r ss u g g e s t t e s t i n g a l o n g w i t h r e l i a b l e e s t i m a t i o n a s t h e e v i -d e n c e o n w h i c h t o b m , e w a t e r p r o o f i n g s t e p s .3 . C u r r e n t A p p l i c a t io n S t a t u s o f T u n n e lW a t e r p r o o f i n C h i n ~ aT h e r e a r e t h r e e m a i n c o n s t r u c t i o n m e t h o d s g e n e r a l l yu s e d i n tu n n e l e n g i n e e r i n g i n C h i n a :

t h e Deep Bur i ed Method , w h i c h i s m a i n l y a d o p t e d f o ru n d e r w a t e r t u n ne l s ; t h e N e w A u s t r i a n T u n n e l M e t h o d ( N A T M ) , w h i c h i sm o s t l y u s e d f o r t u n n e l s i n m o u n t a i n o u s g e ol og y ; a n d t h e S h i e l d T u n n e l M e t h o d, w h i c h i s o f t e n e m p l o y e df o r s u c h m e t r o p o l i t a n s o f t -s o ft u n d e r g r o u n d e n g i n e e r -i n g a s m e t r o .I n m a n y t u n n e l w a t e r p r o o f i n g t e c h n o lo g i e s, a c o m b i n a -t i on o f w a t e r t i g h t l i ni n g , d r a i n a g e s y s t e m , c o n c r e t e g r o u t -i n g a r e t h e m o s t p o p u l a r m e t h o d s o f w a t e r p r o o f i n g i n t u n n e le n g i n e e r i n g .

3.1 Composite LiningC o m p o s i t e l i n in g i s m a d e u p o f t i m b e r i n g , m o u l d i n gc o n c r e te a n d w a t e r p r o o f m e m b r a n e . B e c a u s e o f t s r a t i o n a l -i t y a n d r e l i a b il i ty , i t i s th e m o s t p o p u l a r m e t h o d o f N A T Mi n t h e w o r l d . I t i s a p t t o b e e r e c t e d i n a d r y o r w e t e n v i r o n -m e n t a t l o w e r c o s t, m i d i t s o p e r a t i o n p r o c e s s c a n b e e a s i l yi n s p e c t e d . I n a s u f f i c i e n t l y r e a s o n a b l e t u n n e l o p e r a t i o n , aw a t e r t i g h t t u n n e l c a n b e g u a r a n t e e d . T h e g a s k e t , i f i n -s t a l le d b e t w e e n l i n i n g l a y e r s , s h o u l d b e s t r o n g e n o u g h t ob e a r h y d r a u l i c p r e s s u r e .

W i t h a s m o o t h a n d g l o ss y s u r f a c e , t h e w a t e r p r o o f l a y e ri n a c o m p o s i t e li n i n g , w h i c h i s m o s t l y c o m p o s e d o f P V C ,E C B , E V A , L D P E a n d H D P E , s h o u l d b e f ix e d b e t w e e n t h et i m b e r i n g a n d t h e m o u l d i n g c o n cr e te . T o p r e v e n t t h e w a t e r -t i g ht m e m b r a n e f r o m d a m a g e a n d a s s u r e a r e li a b le w a t e r -p r o o f l a y e r , a 4 - 5 - m m - t h i c k f o a m p l a s t i c l i n i n g o r 2 .6 ~ 3 .2 -m m w a t e r p r o o f i n g g e o - te x t i le s s h o u l d b e p l a c e d b e h i n d t h ew a t e r t i g h t m e m b r a n e , t h e j o i n ts o f w h ic h s h o u l d b e f i x e dw i t h p l a s t i c p i p es , p l a s t i c w a s h e r s , s t e e l w a s h e r s , w o o d e ns c r ew , e tc . T w o p o p u l a r t y p e s o f w a t e r p r o o f o p e r a ti o n s w i t hc o m p o s i t e l in i n g a r e s h o w n i n F i g u r e 3 .T h e c o m p o s i t e l in i n g s o l u t io n h a s b e e n a p p l i e d in m a n yt u n n e l e n g i n e e r i n g p r o j e c t s , s u c h a s t h e T o k y o G u l f U n d e r -w a t e r H i g h w a y T u n n e l , B e i j i n g - X i d a n s u b w a y l in e , a n dB e i j i n g - J i u ji a n g W u z h i s h a n R a i l w a y T u n n e l . B e c a u s e o fp r o b l e m s w i t h t h e p r e v i o u s w a t e r p r o o f i n g m e a s u r e s i n t h eF u j i a n G a n g t u o M o u n t a i n T u n n e l w o r k , w h i c h w a s c o m -p o s e d o f 2 - c m s a n d - p l a s m s m o o t h f a c e , g e o t e x t il e s a n d P Ep l a s t i c w a t e r p r o o f l a y e r , t h e w a t e r p r o o f i n g d e s i g n w a sm o d i f i e d t o a r e p r e s e n t a t i v e c o m p o s i t e l i ni n g w a t e r p r o o f -i n g m e t h o d e f f i c i e n t e n o u g h t o f u l f i l l t h e w a t e r p r o o f i n gr e q u i r e m e n t s .H o w e v e r , th e r e a r e s o m e i n e v i t a b l e d i s a d v a n t a g e s i nt h i s m e t h o d . I t i s r e l a t i v e l y d i f f i c u l t t o p r o t e c t t i m b e r i n gf o r m s i n t h e i n i t i a l s t a g e s , a n d i t r e q u i r e s a l o n g c o n s t r u c -t i o n p e r i o d a n d i s a r a t h e r c o m p l e x o p e r a t i o n t o p e r f o r m .M o r e o v e r, t h e m e a n s o f i t s j o i n t c o n n e c ti o n b e t w e e n w a t e r -p r o o f p l a n k s c a n n o t b e g u a r a n t e e d , a n d f u r t h e r m o r e r e -q u i r e s h i g h - c l a s s w e l d i n g c r a f t . I n a d d i t i o n , t h e w a t e r p r o o fp l a n k i s q u i t e d i f fi c u l t t o fi x o n t h e l a t e r a l t u n n e l , a n d t h u si s p r o n e t o d a m a g e d u r i n g t h e o p e r a t i o n p r o c e s s o f t h es e c o n d li n i n g. T o a c h i e v e a c o m p l e t e w a t e r t i g h t t u n n e l , a sa c o n s e q u e n c e , a c o m p o s i t e l i n i n g w a t e r p r o o f i n g s h o u l du s u a l l y b e c o m b i n e d w i t h s u c h o t h e r w a t e r p r o o f m e t h o d s ,s u c h a s d r a i n a g e a n d g r o u t i n g c o n c r e t e .3.2 Double Lining

D o u b l e li n i n g , w h e r e a s e c o n d li n i n g s e p a r a t e s m o i s t u r ea n d o x y g e n i n t u n n e l s f r o m t h e i n i t i a l l i n i n g , is m a i n l y u s e di n s h i e l d i n g t u n n e l l i n g . B e c a u s e o f t h e d i f f ic u l t i e s o f e n s u r -i n g a w a t e r t i g h t p i p e j o i nt , w h e n a h i g h e r w a t e r p r o o f r a n ki s r e q u i r e d , w a t e r p r o o f p l a n k s m u s t b e i n s e r t e d b e t w e e np i p e s a n d t h e s e c o n d l i n i n g ( s e e F i g . 4) .A d o u b le l i n in g c a n e n h a n c e t h e a n t i - p e r m e a b i l i t y q u a l -i t y o f t h e l i n i n g o w i n g t o i t s s u b s t a n t i a l i t y a n d c o n c r e t er i gi d it y ; w a t e r p r o o f c o n c r et e w i t h h i g h a n t i - p e r m e a b i l i t y

Vo lum e 15 , N um be r '2, 2000 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY 29


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1

5- k l / / i , / i / i , / i / I / it I I I I I i i I I l i I t I I I I I I i l I I i I I I I I I I I I I I t i l ~ 2~ - e 4 * ~ ~ ' ' .

1.RC pipes 2.Waterproofplank(t :2mm ) 3.Second l ining Concrete4 .T ra nserv e sec t io n o f s t o pp ing w a t er co ns t ruct ion 5.geotextiles6.Concrete jo ints

Figure 4 . Double l in ing w aterproo f ing method.

( > $ 8 ) t h e r e f o r e , is r e q u i r e d . H o w e v e r , t h e t i n y w a t e r s e e p -a g e c a r r i e s i m p u r i t i e s t h a t w i l l l e a v e a n u n s i g h t l y s t a i n .M o r e s e r i o u sl y , c o n c r e t e c r a c k s i n t h e c u r i n g p r o c e s s , a n dw a t e r w i ll f in d i t s w a y t h r o u g h e v e n t h e f i n e s t o f c r a c k sr e s u l t i n g f r o m t h e r i g i d i f i c a t io n o f co n c r e t e , d e s p i t e t h ep r o v is i o n of a d e q u a t e d r a i n a g e s y s t e m s i n t h e i n v e r t. I t i st h e c a p i l l a r y e f f e c t w h i c h d r a w s w a t e r i n t o t h e s e f i n e v o i d s.C o n s e q u e nt l y , e x t r a c a r e m u s t b e t a k e n w i t h b o t h t h e l i n i n gj u n c t u r e s a n d c o n s t r u c t i o n j o i n t s i n d e e p - b u r i e d t u n n e l s .T o a s s u r e a l o n g s e r v i c e p e r i o d a n d r e l i a b l e w a t e r p r o o f -i n g a c ti o n o n t h e e n t i r e l i n i n g , e m p h a s i s s h o u l d b e p a i d t ot h e w a t e r - c e m e n t r a t i o n o f t h e c o n c r e t e , a n d c o n s t r u c t i o nj o i n t s s h o u l d b e d e c r e a s e d t o t h e g r e a t e s t e x t e n t p o s s i b l e i no r d e r t o c o n t r o l s h r i n k a g e c r a c k s i n m o u l d i n g c o n c r e t e .F u r t h e r m o r e , c a r e f u l a t t e n t i o n s h o u l d b e p a i d t o w a t e r -p r o o f i n g o f c o n s t r u c t i o n j o i n t s w h e n p h a s e c a s t i n g i s d o n e,a n d t o t r e a t m e n t o f j u n c t u r e s w h e n p r e c a s t b r i c k w o r kl in in g i s u s e d .A s a r e s u l t , t o c r e a t e a w a t e r t i g h t s h i e l d t u n n e l i t i sn e c e s s a r y t o d e c r e a s e c r a c k s i n t h e l i n i n g c o n c r e te ; a s s u r ee x c e l l e n t w a t e r p r o o f i n g d e s i g n a n d c o n s t r u c t i o n o f j o i n t s;a n d i n s e r t a h i g h - q u a li t y w a t e r p r o o f l a y e r b e t w e e n t h el in in g s .F o r e x a m p l e , w i t h a c o m p r e h e n s i v e w a t e r p r o o f i n g d e-s i g n o f o i n t s , l in i n g a n d w a t e r p r o o f i n g c o a t , t h e w a t e r p r o o f -i n g r e q u i r e m e n t s f o r t h e E a s t Y a n ' a n R o a d c r o s s- r i v e rT u n n e l i n S h a n g h a i h a v e b e e n c o m p l e t e l y a c h ie v e d .

3 . 3 S in g le L i n i n gS i n g l e l in i n g , w h i c h i s d i v i d e d i n t o t w o t y p e s o f m e a -s u r e s - n a m e l y , i n n e r l i n in g w a t e r p r o o f i n g a n d o u t e r l i n in gw a t e r p r o o f i n g - - i s a n e x t e n s io n o f t h e N A T M , a s s h o w n i nF i g u r e 5 .F i r s t o f a l l, t h i s t y p e o f l i n i n g i s p e r m e a b l e . A p e r m e a b l ef a s t - s e t t i n g a g e n t m u s t b e e m p l o y e d i n to t h e o u t e r g r o u t -i n g l ay e r , w h i l e t h e i n n e r g r o u t i n g l a y e r m u s t b e w a t e r -t i g h t . A l l h y d r a u l i c p r e s s u r e a c t e d t h e c o n t a c t f a c e b e -

t w e e n t h e i n n e r a n d o u t e r l a y e r a n d s h o u l d b e a b s o r b e d b yt h e w h o l e l i n i n g s y s t e m .I f c o n c r e t e g r o u t i n g i s m i x e d w i t h p a r t i c l e q u a r t z , i t sd e n s i t y a n d a n t i - c a u s t i c i t y w i l l b e i m p r o v e d a n d t h e s t r e n g t ht o r e s i s t c o m p r e s s i o n w i l l b e a l s o e n h a n c e d , b u t i t s r e b o u n dv a l u e w i l l b e l o w e r e d . T h e s p a c i n g r a t i o i n t h o s e m i x t u r e sw i t h p a r t i c l e q u a r t z a r e l a r g e l y r e d u c e d d u e t o i t s h i g hw a t e r - a b s o r b i n g q u a l i t y , w h i l e i t s a b i l it y t o r e s i s t s u l p h a t ea n d c h l o r i d e i s t o s o m e e v e n t s t r e n g t h e n e d .I n a d d i t i o n , a s i n g l e l i n i n g h a s n o e x p a n s i o n j o i n t s .D u r i n g t h e d a n g e r o u s p e r io d o f s t r e n g t h r i s in g o f t h e g r o u t -i n g c o n c r e t e , s t r e s s r e s u l t i n g f r o m s u b s i d e n c e s h o u l d b el o w e r t h a n t h e t e n s i o n s t r e n g t h o f c o n c re t e b y w a y o fd e c r e a s i n g h y d r a t i o n h e a t , s l i g h t l y g r o u t i n g , a n d c u r i n g . A sa c o n se q u e n c e , t h e l o n g i t u d i n a l r e i n f o r c e m e n t w i ll p r e v e n tt h e t u n n e l s t r u c t u r e f r o m s u b s i d i n g s o t h a t t h o s e s p e c if i ce x p a n s i o n j o i n t s a r e u n n e c e s s a r y .F i n a l l y , a s i n g l e l in i n g d o e s n o t r e q u i r e j o i n t s . B e c a u s eo f i t s f a v o r a b l e v i s c i d i ty , c o n c r e t e g r o u t i n g c a n c o m p l e t e l ye l i m i n a t e o p e r a t i o n jo i n t s , w h i c h e n a b l e s t h e s i n g l e j e tt u n n e l f a r f r o m j o i nt s . H o w e v e r , d r a i n a g e w a t e r p r o o f i n g i su s u a l l y u s e d i n c o o p e r a t i o n w i t h o t h e r w a t e r p r o o f i n gm e t h o d s .3 . 4 D r a in a g e W a t e rp r o o fi n g

Predicting the l ikely amo unt of wate r seepage into anunderground structure is first employed o decide on drain-age m e a s u r e s . D r a i n a g e w a t e r p r o o f m e a s u r e s c a n b e e x-e c u t e d a c c o r d i n g t o t h e f o l lo w i n g s t e p s . S t e p 1 . D r a i n i n g p r i o r to l i n i n g . T o e n a b l e t h ew a l l r o c k to d r a i n e a s i ly , a l a r g e a m o u n t o f u n d e r -g r o u n d w a t e r s h o u l d b e g a t h e r e d i n t o a l o n g it u d i n ald i t c h b e f o r e t h e l i n i n g i s c a r r i e d o u t . T h i s m e t h o d c a nb e u s e d a s a l a s t i n g w a t e r p r o o f i n g m e a s u r e t o c ur eu n g r o u t e d t u n n e l s. S t e p 2 . S e t t i n g t h e w a l l r o c k d r a i n a g e g r o o v e .A w a l l r o c k d r a i n a g e g r o o v e c a n b e s e t u p p r i o r t o o ra f t e r t h e l i n i n g i s i n s t a l l e d i n o r d e r t o c o m p l e m e n tb e f o r e h a n d d r a i n a g e , e s p e c i a l l y f o r s e e p a g e t h r o u g hd i f f u si n g , o r to d i v e r t u n d e r g r o u n d s e e p a g e w a t e r i n t ot h e s o f fi t o f t h e l i n i n g s o a s t o d e c r e a s e t h e p e r m e a b l ep r e s s u r e o n t h e l i n i n g . S t e p 3 . P l a c i n g a l i n i n g d r a i n a g e t r e n c h . At r e n c h w i t h v a r y i n g s e c t i o n s c a n b e s e t u p a l o n g o rp e r p e n d i c u l a r t o t h e l i n i n g j o i n t s . I n " T e c h n i c a l S t a n -d a r d o f H i g h w a y E n g i n e e r i n g " ( J T J 0 1 -8 8 ) , t h e l e a s td r a i n a g e s l o p e is s t i p u l a t e d f o r d r a i n a g e m e a s u r e s i nt u n n e l e n g i n e e r i n g . T o a v o i d t o o d e e p a w a l l f o o t in g o rt o o l o w a n e x c a v a t i o n e l e v a t i o n i n t h e b o t t o m o f t h ei n v e r t e d a r c h , a c e n t r a l d r a i n p i p e s h o u l d b e p r o v i d e d

Inner Waterproofing Outer Wa terproofinzr o c k ~ ? h o i c r e t . , h o i c r e t e ~ r o c k

~ " I " ~ w . e . p . o o . . g \WALLS

IINvKIrr

Figure 5 . S ingle l in ing waterproof ing method.

2 3 0 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY V ol um e 15, N u m b er 2, 2000


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for hose tunnels with a n inverted arch or deep-buriedditch. In o r d e r t o e n s u r e t h e concrete lining itho uthydraulic pressure, an outer drainpipe sh ould be setup at the base of ach side of he concrete arch, utsidec o nc re t e l i ni n g a n d w a t e r p r o o f m e m b r a n e s o a s tor e d u c e t h e s e e p a g e w a t e r o u t o f h e t u nn e l s. U s u al l y ,d r a i n a g e w a t e r p r o o f i n g is u s e d i n c o m b i n a t i o n w i t ho t h e r w a t e r p r o o f m e a s u r e s ( s e e Fi g. 6 ).

3.5 Concrete Grouting Waterproof ingConcrete grou t ing waterproofing, jo ints caulk ing an d

l e a k a g e j a m m i n g a r e e m p l o y e d f or s h i e l d t u n n e l s . C o n c r e t eg r o u t i n g c a n i m p r o v e t h e i n t e g r i t y o f t h e w a l l r o c k i nt u n n e l s a n d c a n a m e l i o r a t e h y d r a u l i c p r e s s u r e o n t h e l in -i n g . C h e m i c a l g r o u t i n g a n d p a r t i c l e c e m e n t g r o u t i n g a r et w o k i n ds o f c o m m o n g r o u t i n g m e a s u r e s t h a t c a n b e u s e d toc u r e t h e s e e p a g e o f i~ in is he d t u n n e l s , a s w e l l a s e f f i c i e n t l yp r e v e n t g u s h i n g d u r i n g c o n s t r u c t i o n p e r i o d ( s e e F i g . 7 ) .W h e n c o m m o n so i l s h i e l d i n g a n d e a r t h p r e s s u r e s h i e ld -i n g a r e d r e d g i n g u p , f i l li n g is j e t - g r o u t e d i n t o t h e o u t e rs p a c e o f t h e t u b e ~ L ng t o p r o v i d e t h e c o r r e c t g r o u t i n gt h i c k n e s s. T h i s p r o c e d u r e n o t o n l y p r o t e c t s a g a i n s t t u b es e e p a g e , b u t a l s o e n a~ fl es t h e g r o u t i n g l a y e r t o b r i n g i t s o w nw a t e r p r o o f q u a li t i e s i n t o f u ll p l a y . I f w a t e r t i g h t m a t e r i a l sw i t h l a s t i n g s t a b i l i t y a r e u s e d , c o n c r e t e g r o u t i n g w a t e r -p r o o fi n g c a n r e s u l t i n a p e r m a n e n t w a t e r p r o o f i n g e f f ec t . I na d d i ti o n , c o n c r e te g r o u t i n g c a n b e e m p l o y e d t o t r e a t m o v e -m e n t jo i n t s o f t u n n e l s . F o r e x a m p l e , s a t i s f a c t o r y w a t e r -p r o o fi n g r e s u l t s w e r e a c h i e v e d w i t h t h i s m e t h o d i n t h eB e i ji n g F u c h e n g R o a d U n d e r g r o u n d H e a t i n g P o w e r t u n n e la n d t h e S h a n g h a i D a p u j i a n g R o a d c r o s s - r i v e r t u n n e l .H o w e v e r , t h e r e a r e s o m e d i s a d v a n t a g e s t o t h e c o n c r e teg r o u t i n g w a t e r p r o o f i n g m e t h o d . F i r s t , i t i s t o o e x p e ns i v e .S e c o n d , t h i s m e t h o d i s f a r h a r d e r t o c o n t r o l t h a n o t h e rm e t h o d s ; i n p a r t i c u l a r , i t is d i ff i c u l t t o i n s p e c t t h e i n s t a l l a -t i o n p r o c e d u r e . T h i r d , i t i s a l m o s t i m p o s s i b l e t o r e a l i z e ac o m p l e t e w a t e r t i g h t t u n n e l u s i n g o n l y c o nc r e t e g r o u ti n g . I na d d i t i o n , t h e i n s t a l l a t i o n p r o c e s s i s p r o n e t o i n j u r e t h eo p e r a t o r s . F i n a l l y , i t p o l l u t e s t h e e n v i r o n m e n t . A s a r e s u l t ,c o n c r e te g r o u t i n g i s t a k e n a s a n a c c e s s o r y m e a s u r e t ot u n n e l w a t e r p r o o f i n g in C h i n a . F o r i n s t a n c e , b o t h t y p e s o fw a l l r o c k g r o u t i n g - -r . L a m e l y , i n t h e e n t i r e s e c t i o n p r i o r t ol i n in g a n d c i r c u l a rl y a f t e r l i n i n g ~ a r e e m p l o y e d in t h e B aP a n g L i n T u n n e l .

2

l .S p r in 8 Drain p ip e 2 .Je t con cre t e 3 .W at erp roofl a y e r 4 . M o u l d i n8 Con cre t e 5 .G rain age ap er t u re6 .Cen t ra l d ra ixt p ip e7 .road s m'f ace

Figure 6. Drainage waterproofing.

l .W al l rock s 2 .G rou t in g 3 .P ip es

Figure 7. Grouting in shield tunnels.O b v i o u sl y , s i n ce l i t tl e t u n n e l w a t e r p r o o f i n g r e s e a r c h h a sb e e n c a r r i e d o u t i n r e c e n t y e a r s i n C h i n a , c l a s s i f i c a t i o n o ft u n n e l w a t e r p r o o f i n g r e q u i r e m e n t s i s st il l u n c l e a r i n v a r i-o u s u n d e r g r o u n d t u n n e l s , a n d t h e d e s i g n b a s i s f o r w a t e r -p r o o f i n g i s f a r f r o m s u f f i c i e n t . T h e r e f o r e , i t i s e s s e n t i a l t of u r t h e r i n v e s t i g a t e t h e o p t i m i z a t i on , e c o n o m i c s a n d r a t i o-n a l i t y o f t u n n e l w a t e r p r o o f i n g m e a s u r e s .I n t h e f o ll o w in g s e ct i on s , t h e w a t e r s e e p a g e v o l u m e i nt h e m o u n t a i n t u n n e l i s r e a s o n a b l y e s t i m a t e d b y m e a n s o f ac o u p l in g a n a l y s i s o f t h e f i n i t e e l e m e n t m e t h o d a n d b o u n d-a r y e l e m e n t m e t h o d , w h i c h p r e s e n t s a r e l i ab l e t h e o r e ti c a lb a s i s f o r w a t e r p r o o f i n g m e a s u r e s i n t h e C h o n g q i n gZ h e n g w u s h a n H i g h w a y T u n n e l .

4. Num erical Modeling of Se epa ge Field4.1 Darcy's Law

D a r c y ' s l a w [1] c a n b e e x p r e s s e d a sv , = k ~ - ~ - - k , , - ~ - k , z - ~ - - ( i = x , y , z ) (1 )

ow h e r e v , i s t h e s e e p a g e v o l u m e t h r o u g h u n i t a r e a , a n d k ~,k~y, a n d k ~ a r e , s e p a r a t e l y , t h e s e e p a g e v e c t o r i n t h e d i r e c -t i o n o fx , y , a n d z . I f x a n d y a r e t h e t o t a l p l a n e c o o r d i n a t e a n dz i s t h e p e r p e n d i c u l a r c o o r d i n a t e , t h e h y d r a u l i c f u n c t i o n ish = z + P (2 )

i n w h i c h z is T H E p o s i ti o n h e a d o b t a i n e d f r o m a c e r t a i nn o r m h e i g h t , a n d p i s t h e u n d e r g r o u n d w a t e r p r e s s u r e a ts o m e r e s e a r c h p o i n t, a n d y i s t h e s p e ci f ic w e i g h t o f w a t e r .A s f o r t h e i n c o m p r e s s i b l e f l u id , i t s c o n t i n u o u s e q u a t i o n i sv~ - Q0 = 0 (3)

i n w h i c h Qo i s u n d e r g r o u n d w a t e r r e s o u r c e .I f w e a s s u m e t h a t t h e r e s e a r c h r e g i o n i s a n i de a l h o m o -g e n e o u s m e d i a , t h e n k . k , . k ~ i s c o n s t a n t a n d t h e p a r t i a ld i f f e r e n t i a l e q u a t i o n o ~ s e e ~ a g e f i e ld c a n b e o b t a i n e d .k ~ (~---12 + k i , + Q o = O (4 )

O n t h e b a s i s o f d e t e r m i n a t e b o u n d a r y c o n d it i on s a n dd e v i a t i o n t h e o r y , t h e f o l lo w i n g e x p r e s s i o n c a n b e o b t a i n e dt h r o u g h s o l v i n g e x t r e m u m :

(5 )i n w h i c h Q i s th e u n i t s e e p a g e v o l u m e o n t h e b o u n d a r y ,i s t h e s o l v i n g r e g i o n o n b o u n d a r y F . I f ~ / (h ) i s e q u a l t o z e ro ,t h e n e q u a t i o n ( 4 ) c a n b e o b t a i ne d .

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4.2 F in ite E lement Metho dBased on the Finite Element Method, region ~ isdiscretized into n elements and, in term of element displace-ment function, certain elements of the hydraulic headfunction can be obtained.

h = [N] {h} e (6)Then,

[ K l l h i e + { Q } e = O (7)n = l

where{Q}e is the seepage volume through the boundar y or theseepage volume of equivalent joints from theboundary resource,

[K ]e is the element transmit matrix, and[ K ? =~ve B ] t [ k ] [ B ] d V , in which [k] is the permea bilitycoefficient and [B] is the geometrical matr ix.We assume m joints per element; then

[~N1 a N = i] /~N: 0N~

[B =--~-/0Ni W - (8)

Through assembly into a total matrix, the seepage vol-ume governing equation for finite element analysis can beobtained. [K] {h} = {Q} (9)4.3 Boundary E lement TheoryOn the condition that F is the total boundary( F~ is theboundary of a certain tunnel in region ~ with homogeneouspermeabi lity medium_(its permeabi lit y coeffcient is k), andboth hydraulic head h in partial boun dary F and hydraulichead h / in partial boundary F, can be determined, thenhydraulic he ad function in r egion l-I should confor m to thefollowing Laplas ian expression.

~2h + ~2h ~2h =0 (10)~x 2 - ~ + ~--~-which describes hydraulic head of anypoint in undergr ound three-dimensionalseepage field. Function h(x,y,z) is itssolution and can lead to an equivalenthydraulic head figure.In this paper, the boundary region,which conforms to the above equation, isdiverted into a specific boundary ele-ment. The total matrix is assembled ac-cording to the Finite Element Method,and then the underground water seep-age volume can be convenient ly obtained.The coupling method presente d in thispaper can be applied to problems regard-ing non-homogeneous and nonlinearseepage fields. In th e following section,the seepage field simulation for theChongqing Zhenwushan Tunnels is car-ried out.5 . S e e p a g e F i el d S i m u l a t i o n I nZ h e n w u s h a n T u n n e l sThe numerical code solves the gov-erning equation of seepage field in po-rous media. Because of the symme try ofthe geometry and the boundary condi-

tions, only half the space of the studied domain wasdiscretized. Eight-node isopar ametri c elements with Gausspoints were used. The computational analysis was per-formed for a steady state. The result gives the hydraulicheads at each node and the flow velocities at each Gausspoint.The first step is to analyze the seepage distribution ofmountain mass before excavating tunnels. Where the un-derground water level is the highest, a calculation sectioncontaining the tunnel trans verse section is extracted. Theboundary conditions were fixed after an examination ofevolution of the hydraulic heads. That is, because of quasi-hydrostatic state of the wa ter level above the tunnelsbefore the excavation of tunnel, a cons tant hydraulic po-tential was imposed over the entire field. Thus, the bound-ary hydraulic head h at water level and h under thetunnels are ta ken as bo'undary elements, of whlch h is zero,and h; can be determine d. The per meabi lity coeffici'ent canbe determined. Thus, the potential was prescribed aroundthe tunnels.The second case assumes tha t drainpipes will drain allthe seepage water from the moun tain mass. I n fact, at leastprior to lining, the seepage water in tunnels will nearly bedrained out. In this case, the hydraulic head h , in innerbounda ry of tunnel is zero, meaning tha t no hydraulicpressure was imposed on the lining. The calculated resultsobtained from the first case can be considered as otherboundary conditions in this case. Thus, the contour ofequivalent hydraulic heads at this transverse sectionarou nd the tun nels can be obtained (see Fig. 8). The larges tseepage volume at this studied position amounts to 250.8cnd day ' m 2.In the final case, the NATM or other waterpro of mea-sures are employed so as to guarantee that no seepagewater appears in the in ner s urface of tunnels, or all thedrainpipes around tunnels are blocked. In this case, thetunnel face is impermeable, as is the tunnel lining, and allseepage hydraulic pressure from mountain mass will di-rectly act on the lining of tunn els (see Fig. 9). The re sultindicates that, in the studied section, the greatest hyd rau-lic pressure acting on tunnel surface amo unts to a hydrau-lic head of 81 m.6 . C o n c l u s i o n s a n d C o m m e n t s

It has been prov en that it is nearly impossible to achievea completely watertight tunnel using one waterproofing

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232 TUNNELLINGAND UNDERGROUNDSPACETECHNOLOGY Volume 15, Number 2, 2000


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Figure 9. Seepage equivalent hydraulic heads around tunnels in the case ofno drainage (cm) .method alone, Consequently, multiple waterproofing mea-sures must be integrated in underground works. Onlythrough multiple waterproofing measures and layer uponlayer protection can tunnels without seepage be achieved.The authors r ecommen d that the following principles shouldbe adhered to:

1. Reasonable geological inves tigat ion should be carriedout as far as possible and as much information aspossible obtained from the results of the investigation.2. On the basis of the geological situat ion obtained,prevention, dral~age, cau lking and intercepting shouldsynthetically be, employed to the tunnel waterproof-ing. Rigid waterproofing should be integrated withflexible waterproofing. In addition, each waterproof-ing method should be evaluated according to it par-ticular characteristics with regard to undergroundworks.3. A complex lining or double lining waterproo fing sys-tem should be a top priority and is highly recom-mended. Watertig ht lining should be brought into fullaction and both drainpipes and drain ditches shouldbe reasonably laid out.4. A high-perf ormance waterp roof layer and self-water-proof lining materia ls should be used. Waterproofingtreat ment of joints a nd movement should receivespecial attention.5. Three-dimensio~aal finite elem ent an alysis model hasbeen established in this paper and two-dimensionalanalysis has e~iciently shown the seepage distribu-tion around tunnel sections. To guarantee that no

seepage takes place in tunnels, anti-permeability ratings in correspondingtunnel parts should be stipulated, and acomposite waterproof system should beencouraged.6. Although there are some limitationsin practice, the waterproofing appli-cation in the Zhenwushan Tunnelshows that it is indeed possible toachieve a completely watertight tun-nel. The future development of tun-nel waterproofing should encouragedesigners to use numerical methodsfor better prediction of seepage vol-ume, leadi ng to a economical and rea-sonably watertig ht tunnel.7 . R e f e r e n c e sConstruction Ministry of China. 1988.Waterproof Criterion in UndergroundEngineering (GBJ108-87). Beijing: Con-struction Press.Davis, H.E.; Gunn, M.J.; Mair, R.J .; andSeneviratne, H.N. 1980. The stability ofshallow unnels and underground openingsin cohesivematerials.C-eotechnique30:397-416.

Descoeudres, F. and Rybisar, J. 1987. Ecoulement d'une nappelivre vers un tunnel. Publication de la Socidtd Suisse de Mecaniq uedes Sols et des Roches, 115:3-7.Jaby J.F.; Mahuet J.L.; and Reith J.L. 1998. Improving of Frenchspecifications and techniques in waterproofing for undergroundworks.Proceedings of the World Tunne l Congress'98 on Tunnelsand Metropolises, Sao Paulo, Brazi l, 495-500.Kondoh, Michio ; Matsuike, Takashi ;Kurano, Akiol and Kisaichi,Shin. 1998. Development of he waterproof membrane sprayingmethod in NATM tunnels. Proceedings of the World TunnelCongress' 98 on Tunnels and Metropolises, Sao Paulo, Brazil,515-521.Kriekemans, Bert P. 1998. Polyure hane grouting for sealing leakagein tunnels. Proceedings of the World Tunnel Congress' 98 onTunnel s and Metropolises, Sao Paulo, Brazil, 501-504.Leca, E. and Panet, M. 1998. Application du calcul h la rupture fi lastabilitd du front de taille d'un tunnel. Revue Francaise deGeotechnique 43:5-19.Ministry of Railway. 1986. Design Criterions of Railway Tunnel(TBJ3-85). Beijing: Railway Press.Ministry of Railway of China. 1986. Construction Criterions ofRailway Tunnel (TBJ204-86). Beijing: Railway Press.Ministry of Transportation of China. 1995. Technical Standard ofHighway Engineering (JTJ01-88), Beijing: Jiao Tong Press.Ministry ofTransportation of China. 1990. Design Specification forHighway Tunnel (JTJ026-90). Beijing: JiaoTong Press.Planning Committee of Beijing. 1993. Code for the Design ofMetro(GB50157-92). Beijing:Planing Press.Pellet, Frederic; Desceudres, Francois; and Egger, Peter. 1993. Theeffect of water seepage on the face stability of an experimentalmicrotunnel. Canadian Geotechanical Journal 30,363-369.Wallis, Shani. 1992. Putting paid to water leakage costs. Tunnels& Tunnelling (January 1992),.51-54.

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china tunnel waterproofing

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