The construction of the Vienna Underground Railway and measures taken to protect St. Steven's Cathedral

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The construction of the Vienna Underground Railway and measures

taken to protect St. Steven's Cathedral

Dollerl, A.; Hondl, A.; Proksch, E.; National Research Council of Canada.

Division of Building Research

I S S N 0 0 7 7 - 5 6 0 6

CANADA INSTITUTE I NS1-ITUT CANADI EN

FOR

SCl ENTl FlC AND TECHNICAL DE L'INFORMATION SCIENTIFIQUE

INFORMATION ET 'TECHIVIQUE

NRC/CNR T T - 1 900

TECHNICAL TRANSLATION TRADUCTION TECHNIQUE

THE CONSTRUCTION OF THE VIENNA UNDERGROUND RAILWAY AND MEASURES TAKEN TO PROTECT ST. STEVEN'S CATHEDRAL

MITTEILLINGEN DES INSTITUTES F ~ R GRUNDBAU UND

BODENMECHANIK, TECHNISCHE UNIVERSITAT, WIEN,

TRANSLATED BYITRADUCTION DE D.A. S I N C L A I R

T H I S I S THE TWO HUNDRED AND THIRTY-FIRST I N THE S E R I E S OF TRANSLATIONS PREPARED FOR THE D I V I S I O N OF B U I L D I N G RESEARCH

OTTAWA

1977

National Research Conseil national

T i t l e/Ti t r e :

NATIONAL RESEARCH COUNCIL 0 F CANADA CONSEIL NATIONAL DE RECHERCHE5 DU CANADA

TECHNICAL TRANSLATION

,

TRADUCTION TECHNIQUE

The c o n s t r u c t i o n o f t h e Vienna underground r a i l w a y and measures taken t o p r o t e c t S t . Steven's Cathedral

.

(Der U-Bahnbau und d i e Massnahmen zum Schutz des Stephansdomes)

.

Authors/Auteurs: A. ~ s l l e r l

,

A. Hondl

,

and E . Proksch

ReferenceIReference: M i t t e i l ungen des I n s t i t u t e s f l r Grundbau und Bodenmechani k, Technische U n i v e r s i t d t , Wien, 1 4 (112-4): 19-26, 1976. Translator/Traducteur: D .A. S i n c l a i r Canada I n s t i t u t e f o r I n s t i t u t canadien de S c i e n t i f i c and Technical 1 ' i n f o r m a t i o n s c i e n t i f i q u e e t I n f o r m a t i o n technique Ottawa, Canada KIA OS2

PREFACE

Tunnel 1 in g f o r t r a n s p o r t a t i o n , pub1 i c u t i 1 i t i e s , water supply, and o t h e r purposes i s becoming more and more i m p o r t a n t w i t h i ncreasing u r b a n i z a t i o n . The OECD ( O r g a n i z a t i o n f o r Economic Co-operation and Development) has e s t i m a t e d t h a t t h e minimum demand f o r such c o n s t r u c t i o n i n t h e U n i t e d S t a t e s d u r i n g t h e 1970's w i l l t o t a l almost $12 b i l l i o n . The maximum demand c o u l d be s e v e r a l times t h i s amount. Underground c o n s t r u c t i o n i n Canada i s growing i n a s i m i l a r f a s h i o n . T h i s paper p r o v i d e s a v a l u a b l e case r e c o r d o f t h e measures t a k e n t o p r o t e c t an h i s t o r i c c a t h e d r a l from damage due t o c o n s t r u c t i o n o f t h e Vienna underground r a i l w a y . The r e p o r t o u t 1 i nes t h e i n v e s t i g a t i o n o f t h e sub-surface c o n d i t i o n s and t h e s t r u c t u r a l c h a r a c t e r o f t h e b u i l d i n g as a b a s i s f o r s e l e c t i n g t h e c o n s t r u c t i o n method. The e x e c u t i o n o f t h e p r o j e c t i s d e s c r i b e d and i t s i n f l u e n c e on t h e b u i l d i n g was monitored throughout. I t i s o f much i n t e r e s t t o t h e c o n s t r u c t i o n i n d u s t r y g e n e r a l l y and t h i s t r a n s l a t i o n i s t h e r e f o r e made a v a i l a b l e by t h e N a t i o n a l Research C o u n c i l . We a r e i n d e b t e d t o M r . D.A. S i n c l a i r f o r t h e t r a n s l a t i o n and t o D r . J.H.L. Palmer o f t h i s D i v i s i o n who reviewed t h e manuscript. Ottawa December 1977 C

.

B. Crawford D i r e c t o r D i v i s i o n o f B u i l d i n g Research

THE CONSTRUCTION OF THE VIENNA llNDERGROUND RAILWAY AND MEASURES TAKEN TO PROTECT ST. STEVEN'S CATHEDRAL

SUMMARY

The s t a t i o n p i p e s f o r t h e "Stephansplatz" s t a t i o n 1 i e a t a d i s t a n c e o f o n l y 5 m f r o m Vienna's g r e a t e s t c u l t u r a l monument, S t . Steven's Cathedral. The f o u n d a t i o n s o f t h e "Pagan Towers" go down t o a d e p t h o f t h r e e meters and r e s t , t o some e x t e n t , on s e t t l e n i e n t endangered l o e s s s o i l . Before t h e c o n s t r u c t i o n work on t h e underground r a i l system was begun, a thorough i n v e s t i g a t i o n was made o f t h e p e c u l i a r i t i e s o f t h e c a t h e d r a l and i t s r e a c t i o n t o t h e c o n s t r u c t i o n work, and t h e e n g i n e e r i n g o f t h e underground system was planned t a k i n g these f a c t o r s i n t o account. 'The p l a n n e r s foresaw t h e use o f bored p i l e w a l l i n g and i n j e c t i o n m a t e r i a l as t h e b e s t means o f s e p a r a t i n g t h e s o i l d i r e c t l y a f f e c t e d by t h e c o n s t r u c t i o n work f r o m t h a t beneath S t . S t e v e n ' s . The s t r e s s and s e t t l e m e n t o f t h e former, i t was reasoned, would, i n t h i s way, have t h e l e a s t p o s s i b l e i n f l u e n c e upon t h e l a t t e r . A d d i t i o n a l measures taken i n c l u d e s h i e l d t u n n e l i n g w i t h compressed a i r compensation t o p r o t e c t t h e immediate v i c i n i t y o f t h e endangered zone, l o w - v i b r a t i o n e r e c t i o n o f t h e bored p i l e w a l l s f o r t h e a d j o i n i n g open c o n s t r u c t i o n p i t s , and r e s t r i c t i o n o f p i t w a l l deformation. Measurements t a k e n o f t h e c a t h e d r a l ' s r e a c t i o n w i t h r e s p e c t t o s e t t l e m e n t , s l o p e and v i b r a t i o n d u r i n g t h e t u n n e l c o n s t r u c t i o n proved t h e measures

THE PROBLEM

The " S t e p h a n s p l a t z " ( S t . S t e v e n ' s Square) underground s t a t i o n 1 i e s a t a d e p t h o f a b o u t 26 m ( t u n n e l f l o o r ) , a b a r e 5 m away f r o m t h e west facade o f S t . S t e v e n ' s C a t h e d r a l , V i e n n a ' s most i m p o r t a n t c u l t u r a l monument. W h i l e most o f t h e b u i l d i n g f o u n d a t i o n s i n t h e h i s t o r i c a l c o r e o f t h e c i t y , owing t o t h e i r n o r m a l l y 2- o r 3 - l e v e l basement d e s i g n , had been c o n s t r u c t e d a t c o n s i d e r a b l e depths, j u s t above t h e Q u a t e r n a r y groundwater t a b l e i n t h e g r a v e l

,

t h e v e r y h e a v i l y s t r e s s e d (up t o 80 ~ ~ / m ' ) * C a t h e d r a l f o u n d a t i o n s a r e o n l y 3 m deep, r e s t i n g f o r t h e most p a r t o n s e t t l e m e n t - p r o n e l o e s s . Undisturbed, dense g r a v e l was found beneath t h e f o u n d a t i o n s o n l y a t t h e southwest c o r n e r . N e i t h e r t h e c h u r c h basement o f t h e c a t h e d r a l n o r t h e s o - c a l l e d catacombs e x t e n d t o t h e v i c i n i t y o f t h e west f a c a d e ( F i gure 4 ) .

The qua1 i t y o f t h e masonry w i t h r e s p e c t t o t h e stones and t h e cement employed i n t h e c a t h e d r a l f o u n d a t i o n s ( F i g u r e 1 ) was i n v e s t i g a t e d by A, K i e s l i n g e r (1949 and 1971) and v a r i e d g r e a t l y , depending o n t h e v a r i o u s t i m e s o f c o n s t r u c t i o n . Many d i f f e r e n t s i z e s o f stones were used, r a n g i n g f r o m s l a b s o f r o c k and s m a l l e r p i e c e s o f s t o n e up t o b o u l d e r s 1 m i n d i a m e t e r . The c e n t r a l Romanesque s e c t i o n w i t h t h e G r e a t P o r t a l (Ri e s e n t o r ) and t h e two Pagan Towers (HeidentUrme) r e v e a l s t h e u s e o f c a l c a r e o u s sandstones, L e i th a 1 imestones, q u a r t z sandstones f r o m t h e f l y s c h zone and numerous remnants o f R O M ~ encampment w a l l s , P l a c e s were found w i t h good m o r t a r , b u t o f t e n t h e r e was much t o o l i t t l e , o r t h e m o r t a r was washed o u t o r e n t i r e l y absent. Two l a r g e G o t h i c c h a p e l s ( E l i g i u s and H o l y Cross) were added on a b o u t 1340, and w h i l e t h e i r f o u n d a t i o n s a r e i n d e e d more r e c e n t , t h e y show no e s s e n t i a l d i f f e r e n c e s f r o m t h o s e i n t h e Ronanesque c e n t r e s e c t i o n . I n s p i t e o f s e p a r a t i n g j o i n t s between t h e G o t h i c and Romanesque f o u n d a t i o n s , no uneven s e t t l e m e n t phenomena c o u l d be observed. S t . S t e v e n ' s Square 1 i e s a t a n e l e v a t i o n o f +14.5 m WN t o d 5 . 5 m WN (WN = Vienna datum = 156.68 m above t h e A d r i a t i c Sea) o n t h e "City t e r r a c e ' ' f r o m t h e R i s s g l a c i a l p e r i o d . A1 ong w i t h Romanesque and mediaeval f o u n d a t i o n s and b a c k f i l l s down t o a d e p t h o f 1 0 m and more, t h e r e a r e u n d i s t u r b e d Q u a t e r n a r y

d e p o s i t s which i n p l a c e s extend t o t h e present-day s u r f a c e . Below and a l o n g s i d e t h e Cathedral t h e Quaternary sediments, w i t h an average t h i c k n e s s o f 1 4 t o 16 m, b e g i n w i t h 2

-

2.5 m o f d a r k b u r i a l -ground s o i l ( F i g u r e 3 ) . Next come "1 oess" and a l l loess-loam v a r i a n t s , 4

-

5 m t h i c k , c o n s i s t i n g o f h i g h l y compacted, ye1 low, f i n e sandy s i l t s w i t h numerous c h a r a c t e r i s t i c s o f genuine l o e s s ( h i 1 ls i d e 1 oess) such as s e n s i t i v i t y t o subsidence ( F i g u r e 6 ) ,

l a r g e l y homogeneous s t r a t i f i c a t i o n and calcareous c a p i l l a r i e s (pseudomycel ium)

.

Accordi rrg t o A. K i e s l i nger (1 971) t h i s i s t h e t y p e known as " b a s i n loess", which 1 acks t h e f r i a b l e cohesion o f t y p i c a l h i 1 ls i d e l o e s s . Thus, t h e "deep t r e n c h t 1 and t h e water course o f t h e "Rotenturm" brook r u n n i n g i n f r o n t o f t h e Great P o r t a l , which had been b a c k f i l l e d , were t y p i c a l l o e s s r a v i n e s . Red-brown loamy round r u b b l e stones have been embedded i n places i n t h e loess-loam s e r i e s as a r e s u l t o f r e c e n t e r o s i o n and.accumulation. Below t h e l o e s s t h e r e i s t y p i c a l f l a t r u b b l e from t h e nearby sandstone h i l l y r e g i o n o f t h e Vienna Woods, w i t h wide-ranging g r a i n s i z e and i n a l t e r n a t i n g open o r h e a v i l y loamed l a y e r s down t o approximately +3 m WN, i n t e r r u p t e d by a 0.9 t o 2.0 m t h i c k l a y e r o f y e l l o w s i l t and f i n e sand which i s o f t e n s e r r a t e d o r loosened up w i t h 1 enses o f r u b b l e ( 1 ower boundary +2.7 m t o 4.25 m WN). The 1 0

-

11 m t h i c k ice-age r u b b l e complex ( l o c a l r u b b l e ) comes t o a n end i n t h e l o w e r p a r t w i t h o l d e r , n o t very e r o s i o n - s u s c e p t i b l e , non-loamy q u a r t z and c r y s t a l 1 in e round r u b b l e s o f

v a r y i n g sandiness w i t h a groundwater b e a r i n g l a y e r about 1 . 5 m and more i n t h i c k n e s s . The boundary between t h e Q u a t e r n a r y and T e r t i a r y a t a depth o f 14

-

16 m (-0.4

m

WN t o -1.55 m WN, and i n boreholes up t o + 0.4 m WN) i s

c h a r a c t e r i z e d by a coarse 1 ayer o f stones g r e a t e r t h a n 250 mm i n diameter.

Iq t h e s t r a t u m immediately u n d e r l y i n g t h e Quaternary, t h e M i d d l e Pannonic Viennese marl c o n t i n u e s t o g r e a t depths (Congerian marl, Middle P1 iocene-Late T e r t i a r y ) i n t h e f o r m o f a v e r y s i l t y , s t i f f c l a y t o c l a y e y s i l t , grey-brown t o grey-blue, i n t e r r u p t e d by d i s t i n c t 1 ayers o f f i n e sand 0.5 cm t o 25 cni t h i c k . I n t h e excavation and t u n n e l areas these sandy s t r a t a d i p v e r y g e n t l y t o t h e n o r t h and i n c r e a s e i n t h i c k n e s s o v e r a s h o r t d i s t a n c e from 0 t o 10 cm w i t h v a r y i n g groundwater b e a r i n g and e r r a t i c pressure c o n d i t i o n s . The s t i f f marl

,

which i s d i v i d e d by bedding j o i n t s and

deeply s l o p i n g t e n s i o n and shear f r a c t u r e s was found t o be e x t r a o r d i n a r i l y s t a b l e . The perched second groundwater s e r i e s uncovered a t about 31 m depth (-16 m t o -17

m

WN), c o n s i s t i n g o f fine-sandy, s l i g h t l y c l a y e y s i l t (Table

I) i s noteworthy. The p r e s s u r e curves o f t h e f i r s t and second groundwaters were approximately t h e same, v a r y i n g b e f o r e t h e s t a r t o f c o n s t r u c t i o n from

30

-

50 cm i n t h e f i r s t groundwater and o n l y 20

-

30 cm i n t h e second. However, t h e second groundwater showed 1 arge v a r i a t i o n s o f pressure ( F i gure 8) i n d i f f e r e n t phases o f c o n s t r u c t i o n (bored p i l e i n s t a l l a t i o n , pressure g r o u t i n g )

.

The s o i l -mechanical p r o p e r t i e s o f t h e formations represented i n s o i l p r o f i l e BL 314 ( F i g u r e 3 ) can be d e r i v e d f r o m T a b l e s I and 11. The c o m p a r a t i v e l y h i g h r e l a t i v e s e t t l e m e n t o f i = 5 % i n t h e l o e s s i s s t r i k i n g and portended an eventual s e t t l e m e n t o f as much as 8 cm, given t h e e x i s t i n g l a y e r t h i c k n e s s ( F i g u r e 6 ) . I n t h e g r a v e l s t r a t a a r e g i o n o f anomalous granulometry o f 0.4

-

2 mm i s noteworthy ( F i g u r e 7 ) . The marl, a p a r t from t h e sandy s t r a t a embedded i n i t , as a s l i g h t l y t o h i g h l y cohesive, f i n e - g r a i n e d s o i l , i s a medium p l a s t i c , s t i f f c l a y t o medium p l a s t i c , semi-compact s i l t . I t s g e o l o g i c a l p r e s t r e s s i n g can be e s t i m a t e d from

2

l a b o r a t o r y i n v e s t i g a t i o n s t o be o f t h e o r d e r o f 200 Mp/m (A. Casagrande's e s t i m a t e ) . The s t i f f n e s s c o e f f i c i e n t o b t a i n e d f r o m t e s t s ( i n i t i a l l o a d i n g )

2

v a r i e s between 2,000

-

5,000 Mp/m (maxirmm 8,000 ~ ~ / r n ' ) and does n o t depend l i n e a r l y on t h e depth. I n t h e medium p l a s t i c s i l t s a u n i a x i a l compressive s t r e n g t h o f about 20 ~ ~ was obtained, t o g e t h e r w i t h a p e r m e a b i l i t y / m ~ c o e f f i c i e n t o f 1 0 - ~ m / s . I n t h e medium p l a s t i c t o e x t r e m e l y p l a s t i c c l a y s t h e u n i a x i a l compressive s t r e n g t h v a r i e s between 20

-

90 ~ ~ and t h e / m ~ p e r m e a b i l i t y c o e f f i c i e n t f r o m 1 0 - I ' t o 1 0 - l o m/s. The average a n g l e o f i n t e r n a l f r i c t i o n deduced f r o m t h e r o u t i n e Viennese t e s t s ( E = c o n s t ) i s

28'. W i t h repeated s h e a r i n g these angles a r e reduced t o one h a l f and o f t e n l e s s .

POSSIBLE SOLUTIONS

To s o l v e t h e problem, t h e r e was a c h o i c e o f s e v e r a l p o s s i b i l i t i e s . Because o f t h e s ~ l l amount o f i n f o r m a t i o n a v a i l a b l e , f i r s t o f a l l a r e l o c a t i o n o f t h e r o u t e f a r t h e r away from t h e Cathedral was contemplated. An e l e v a t i o n o f t h e r o u t e was a l s o i n v e s t i g a t e d , b u t was r e j e c t e d on account o f t h e deep sub-basement complex i n t h e a d j a c e n t s e c t i o n s . Since removal o f t h e s t a t i o n would be d e t r i m e n t a l t o i t s f u n c t i o n i n g and would r a i s e o t h e r f o r m i d a b l e problems, an a t t e m p t was made t o r e n d e r t h e o r i g i n a l s o l u t i o n feas-i b l e w i t h t h e a i d o f every conceivable supplementary p r e c a u t i o n . F i r s t o f a l l , i t was decided t o change, d i r e c t l y i n f r o n t o f t h e Cathedral, f r o m t h e o r i g i n a l l y proposed open c u t c o n s t r u c t i o n method t o a s h i e l d t u n n e l i n g o p e r a t i o n . Open c u t s were r e t a i n e d o n l y i n t h e a d j a c e n t areas ( F i g u r e 5 ) . Since t h e danger o f s o i 1 c o l l a p s e d u r i n g t u n n e l d r i v i n g c o u l d n o t be r u l e d o u t and because o f t h e importance o f t h e Cathedral, a d d i t i o n a l p r e c a u t i o n s were taken. As f a r as p o s s i b l e , t h e r e was t o be no m o d i f i c a t i o n o f t h e h i s t o r i c a l c o n t i n u i t y o f t h e Cathedral, i n c l u d i n g i t s foundations. 'This requirement r u l e d o u t t h e use o f anchor p i l e s and u n d e r p i n n i n g s e c t i o n b y s e c t i o n w i t h a 1 ongi t u d i n a l g r a t i n g and r e i n f o r c e m e n t o f t h e foundations. It was n o t p o s s i b l e t o achieve any improvement o f t h e Cathedral f o u n d a t i o n

i t s e l f through precautions, because any underpinning s o l u t i o n s by means o f pressure g r o u t i n g o r s t r u c t u r a l measures e n t a i l e d t o o h i g h a r i s k f o r t h e Cathedral. Moreover, a s o l u t i o n was p r e f e r r e d i n which i t was n o t necessary t o i n v o l v e t h e i n t e r i o r o f t h e Cathedral. F i n a l l y , t h e m e t h o d w h i c h w o u l d e n t a i l t h e l e a s t r i s k was sought. We were convinced t h a t a p r o t e c t i v e w a l l o f bored p i l e s would c o n s t i t u t e t h i s optimum s o l u t i o n ( F i g u r e 2 ) . I n t h i s way we hoped, f o r t h e most p a r t , t o separate t h e s o i l volume immediately i n v o l v e d i n t h e b u i l d i q g o p e r a t i o n s w i t h i t s s t r e s s e s and s e t t l e m e n t s , from t h e volume o f s o i l beneath t h e Cathedral, and thus, i n t h e event o f a t u n n e l c o l l a p s e , t o p r e v e n t a dangerous l o s s o f s u b s o i l f r o m beneath t h e Cathedral.

EXECLITION

I n November 1970, t h e C i t y o f Vienna asked t h e F a c u l t y o f C i v i l Engineering and A r c h i t e c t u r e o f t h e Vienna P o l y t e c h n i c a l I n s t i t u t e (Technische Hochschule Wien) t o make an e x p e r t a p p r a i s a l w i t h a view t o dependably a v o i d i n g a l l danger t o t h e Cathedral i n t h e p u b l i c i n t e r e s t . Professors H. Borowicka, A. K i e s l i n g e r , E. Schischka and E. Tremmel

,

who were e n t r u s t e d w i t h t h e a p p r a i s a l , s t a t e d t h a t t h e F a c u l t y deemed t h e measures proposed by t h e C i t y o f Vienna t o be fundamentally adequate. I n a d d i t i o n , o t h e r supplementary measures were suggested which would enable any danger t o be recognized promptly, so t h a t countermeasures c o u l d i n ~ m e d i a t e l y be i n i t i a t e d . T h i s i n v o l v e d p r i m a r i l y t h e i n s t a l l a t i o n o f measuring devices, s p e c i a l o v e r l a y s d u r i n g t h e c o n s t r u c t i o n work, and f i n a l l y , t h e s u p e r v i s i o n o f o p e r a t i o n s by an independent engineer who, l i k e t h e government s u p e r v i s o r on 1 arge hydraul i c p r o j e c t s , would, regard1 ess o f t h e d a i l y progress o f c o n s t r u c t i o n , be p e r s o n a l l y r e s p o n s i b l e f o r t h e safety o f t h e Cathedral. The p r o f e s s o r s named above and C i v i l Engineer F. Liebscher, who was appointed s u p e r v i s o r , t o o k o v e r t h e r e s p o n s i b i l i t y o f a d v i s i n g and s u p e r v i s i n g t h e c o n s t r u c t i o n o p e r a t i o n s i n s o f a r as t h e y i n v o l v e d t h e Cathedral

.

The f i f t y p i l e s c o n s t i t u t i n g t h e p r o t e c t i v e w a l l were produced by t h e r o t a r y d r i 11 i n g method w i t h c o n t i n u o u s l y advancing casing, w h i l e c o n t i n u o u s l y checking t h e behaviour o f t h e Cathedral. I n o r d e r t o preserve groundwater comnunication, a space o f a t l e a s t 10

-

30 cm, f o r a p i l e diameter o f 90 cm, was l e f t between p i l e s . Then t h e w a l l s o f t h e open-cut s w i t c h i n g s h a f t and o f t h e deep open c u t ( F i g u r e 4) were produced by t h e same method. To guard a g a i n s t t h e p o s s i b i l i t y o f a blow-out d u r i n g s h i e l d d r i v i n g w i t h compressed a i r , and t o p r o v i d e s p e c i a l support o f t h e p r o t e c t i v e w a l l i n t h e v i c i n i t y o f t h e Pagan Towers, a slab-shaped zone i n t h e Quaternary was r e i n f o r c e d , and two diaphragms were produced by pressure g r o u t i n g . F o r t h e d r i v i n g o f t h e s t a t i o n s h i e l d , t h e T e r t i a r y was pressure

grouted ( F i g u r e s 2 , 4 and 5 ) . From t h e p a r t i c u l a r l y l a r g e q u a n t i t y o f g r o u t i n g m a t e r i a l consumed i n t h e r e g i o n o f t h e western s t a t i o n tubes, i t i s assumed t h a t a n c i e n t , u n f i l l e d c a v i t i e s must have been present. Minimum w a l l movement was achieved d u r i n g e x c a v a t i o n o f t h e open c u t by c a r e f u l appl i c a t i o n o f p r o v i s i o n a l reinforcement h o r i z o n s . Re1 i e f o f water pressure i n t h e second groundwater t a b l e was accomplished by i n s t a l l i n g pipes. Owing t o t h e v e r y l a r g e s i z e o f t h e deep open c u t , e x c a v a t i o n was executed i n o n e - t h i r d s e c t i o n s . Tunnel d r i v i n g i n t h e s t a t i o n area was c a r r i e d o u t w i t h a hand s h i e l d , w i t h corrrpressed a i r a t 0.5 atm. gauge.

CONCLUSIONS

The v e r y e x t e n s i v e o b s e r v a t i o n s o f s e t t l e m e n t s , v i b r a t i o n s and i n c l i n a t i o n s a t almost a l l i m p o r t a n t p o i n t s i n t h e Cathedral showed t h a t t h e p r o t e c t i v e measures taken had proved e n t i r e l y adequate, and none o f t h e measured v a l ues came anywhere near exceedi ng t h e pernii s s i b l e range ( Fi gure 1 1 ) . Most of t h e s e t t l e m e n t s measured a r e t r a c e a b l e t o t h e p r o d u c t i o n o f t h e bored p i l e w a l l s owing t o t h e unavoidable v i b r a t i o n s a s s o c i a t e d w i t h t h i s method o f c o n s t r u c t i o n and t h e d i s t u r b a n c e t o t h e e x i s t i n g s o i l e q u i l i b r i u m w i t h i t s m o d i f i c a t i o n s . Loss o f s o i l and loosen-ing w i l l a l s o have played an i m p o r t a n t p a r t . The major i n f l u e n c e , however, arose f r o m t h e f a c t t h a t t h i s was t h e f i r s t measure taken and t h e one t h a t was a p p l i e d c l o s e s t t o t h e Cathedral. Once t h e p r o t e c t i v e w a l l was completed, t h e s a f e t y o f t h e Cathedral i n r e 1 a t i o n t o t h e remaining c o n s t r u c t i o n o p e r a t i o n s was s i g n i f i c a n t l y i ncreased. As expected, s h i e l d d r i v i n g w i t h compressed a i r was r e s p o n s i b l e f o r o n l y a small s e t t l e m e n t component. The v i b r a t i o n s measured i n t h e course o f t h i s work were i n s i g n i f i c a n t . Nor d i d e x c a v a t i o n o f t h e deep open c u t cause any i n c r e a s e o f s e t t l e m e n t . The simultaneously executed p r e s s u r e g r o u t i n g s w i t h presumed

1

i f t i n g e f f e c t s , make i t i m p o s s i b l e t o e s t i m a t e t h i s component w i t h any accuracy. The d i s t r i b u t i o n o f s e t t l e m e n t s w i t h r e s p e c t t o l o c a t i o n ( F i g u r e 12) shows general evenness w i t h a p r e d i c t a b l e maximum a t t h e n o r t h Pagan Tower owing t o t h e p r o x i m i t y o f t h e s w i t c h s h a f t . The s h i e l d d r i v i n g process p r o b a b l y had no e f f e c t .

The d i s t r i b u t i o n o f s e t t l e m e n t s a l o n g t h e l o n g i t u d i n a l a x i s o f t h e Cathedral shows d i s c o n t i n u i t y i n t h e r e g i o n o f t h e p r o t e c t i v e w a l l ( F i g u r e 9 ) , b u t d i r e c t comparison w i t h t h e areas on b o t h s i d e s o f t h e w a l l cannot be made s a t i s f a c t o r i l y o n account o f i n f l u e n c e s o f d i f f e r e n t k i n d s . For t h e

c o n s t r u c t i o n o p e r a t i o n s t h e upper v i b r a t i o n 1 im i t was p u t a t an a c c e l e r a t i o n

2

o f b = 20 cm/sec

.

F o r continuous loading, 2 cm/sec2, and occasional

l o a d i n g , 5 cmjsec2, were t a k e n t o be acceptable. Observations o f these l i m i t s proved adequate. The 136.7 m h i g h South Tower i s f a r o u t s i d e t h i s narrower s e t t l e m e n t range. Compared w i t h i t s long-term r a t e o f settlement, t h e i n c r e a s e i s i n s i g n i f i c a n t , ( F i g u r e 10).

References

B a c h l e l t n e r , R . ( 1 9 6 6 ) : "Der U i e n e r Dom" W i e n e r Dom-Verlar, Y i e n B a l o ~ h , I . ( 1 9 7 0 ) : " G u t a c h t e n i i b e r d e n Bau- z u s t a n d v o n S t . S t e p h a n U , u n v e r o f f e n t l i c h t

Borowicka,II. ( 1 9 6 3 ) : "Der '.\riener R o u t i n e - s c h e r v e r s u c h " , M i t t e i l u n c d e s I n s t i - t u t e s f u r G r u n d b a u und Bodenmechanik T.H.Wien, I I e f t 5 Borowicka,H. (1970) : " 1 0 J a h r e W i e n e r R o ~ ~ t i n e s c h e r v e r s u c h " , M i t t e i l u n ~ e n d a s I n s t i - t u t e s f u r G r u n d b a u und Rodenmechanik T.h. Wien, H e f t 11 B u n d e s v e r s u c h s - u n d " R e s o n a n z r n e s s u n ~ e n i m F o r s c h u n g s a n s t a l t B e r e i c h d e r E l i c i u s - A r s e n a l , Wien ( 1 9 7 4 ) : k a p e l l e d e s S t e p h a n s - d o m e s " , u n v e r o f f e n t l i c h t D o l l e r l , A . ( 1 9 7 0 ) : " D i e R a u c r u n d u n t c r - s u c h u n g e n f u r d e n W i e n e r U-Bahnbau", Der A u f b a u H e f t ?/h, Wien P a k u l t 5 t f u r " G u t a c h t e n u h e r d e n A r c h i t e k t u r und S c h u t z d e s Domes v o n B a u i n ~ e n i e u - w e s e n S t . S t e p h a n wtihrend d e s T.H. Wien (1971): B a u e s d e r U-Bahn", u n v e r o f f e n t l i c h t F i s c h e r , K . ( l 9 5 0 ) : " T e c h n i s c h e r B e r i c h t , S u d t u r n S t . S t e p h a n "

,

G e w i c h t e b e r e c h n u n g e n , u n v e r o f f e n t l i c h t Grundbau d r r S t n d t " B e r i c h t i i b e r d i e z u e r - Y i e n

-

MA 2 9 ( 1 9 6 9 ) : w n r t e n d e n SchutzmaRnah- men f u r d e n Dom z u S t . S t e p h n n a n l a l l l i c h d e s U-nahnbaues", u n v e r o f f e n t l i c h t S i n g e r ( 1 9 3 2 ) : S t o p e r e r , K . ( 1 9 7 5 ) : Versuc1.s- 1 ~ n 6 F o r s c h u n r s a n s t a l t d e r ., Gtad t b'j e n , I'A 39 ( 1 9 7 1 h i s 1 9 7 3 ) : , t ~ ~ l i t a c l i t e n

.

G n l ~ c r u n r ! S t ~ p h a n s p l a t z " , u n v e r - o f f e n t l i c h t " G e o l o r i e v o n ' i i e n , I::urzfessur,f. IgL.'+", I I o l l i n ~ k - 3 o r n t r a e p ? q , Lli e n - E e r l i n "h~rr,ct;l i ~ i j b e r j c ; l t - Sc.hiit ~rna?~nat;rr,cr, G t . Z t e p l ~ a n " , u n v e r - i<f f r ? r i t l i c h t

"Geol o c i s und U-Bahnhal~ i n Wien", Der A u f b a u , IleTt; 1 1 / 1 2 , l : i e n " 3 e r i c h t 6 - s _aonbau- m c i r t p r s i i b e r d ~ n E i r t , c i t s f o r t s c h r i t t " , Z 6 , i t s c h r i f t " k r Don", 7 r . _{. r l e n , I i s f t 2} " E r s c h i i t t . e r u n r s - messllngen am . ' ) t ~ p h a n C - dom", u n v e r o f f e n t l . i c h t "Uas u n t a r i r d j s c h e L'ien i m 3 p z u p a u f d s n Bau k u n f t i c e r U n t e r - ~ r u n d b a l . n e n " . Z e i t - s c h r i f t CIAV; 'A'ien, H e f t 9/70 W i e n e r S t a d t v e r - " t I e i f , u n g s - und L i b e l l e n - messunE;, KA 41 ( 1 9 7 1 ) : r n e s s u n g e n " , u n v e r o f f c n t l i c h t

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