A new water tube level for measuring the settlement of buildings

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A new water tube level for measuring the settlement of buildings

Peckover, F. L.

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NATIONAL RESEARCH

COUNCIL

CANADA

A NE1,f WATER TIIBE I,EVEL

FOR MEASURING

THE SE[TLE}@I[T OF BIIILDI}IES

by

F ' . L. Peckover

;

: ANAtyZSD

Febnuary 1952

T e c h n l c a l _{R e p o n t N o . 1 I} of the D l v l s l o n o f B u l l d l n g R e s e a n c h OTTAWA D B R N o . ZB

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PREFACE

T h e s e t t l e m e n t o f b u L l d l n g s l s u s u a l l y o f s o s m a l l a n o r d e r that lt eannot be notlced by the casual o b s e n v e r a n d ls lnslgnlflcant _{f r o m t h e s t r i r c t u r a L} p o l n t o f v t e w . _{A l l o r d l n a r y b u i l d l n g s} _{f o u n d e d c n c o m p r e s s l t l e} _{s o L l s ,} h o w e v e r , d o s e t t l e f r o m t h e i r o r i g l n a l e l e v a i l o n . w h e n s e t t l e r n e n t _{l s e x c e s s l v e o r w h e n s e t t l e m e n t} _{o f o n e p a r t o f a} u u l r $ ! ! s d l f f e r s a p p r e c l a b l y _{f n o m t h a t o f a n y o t h e r p a r t of} a b u l 1 d 1 n 6 , s t r u c t u r a l f a 1 l u r e m a y r e s u l t a n d r n u e h t r o u b l e m a y b e e x p e r l e n c e d " T h e p r o c e s s o f s e t t l e m e n t o f c o m p n e s s l b l e s o i l s l f a _ c o m p l e x m a t t e r and one not yet complelely determi.ned" T h e D l v l s l o n _{o f B u l l - d l n g R e s e a r c h i s t h e r e f o r 6} _{l n t e n e s t e d} l n t h l s p r o b l e m and ls anxlous to make some eontrlbutlon t o g e n e r a l u n d e r s t a n d l n g o f t h e p h e n o m e n o n .

A g o o d s t a r t l n g p o l n t for thls ls the observatlon o f s e t t l e m e n t s _{w h i c h d o o c c u r l n a c t u a l bulldlngs} _{f o u n d . e d} o n e l a y s o l l s " T h n o u g h t h e c o - o p e r a t l o n _{o f t h e o w n e r s o f} b u i l d l n g s _{1 n b o t h o t t a w a a n d Toronto,} _{a s t a r t} _{h a s b e e n m a d e} b y t h e D l v l s l o n a t s u c h o b s e r v a t l o n s " T o f a c l l l t a t e _{t h l s w o r k , M r . F " L " p e c k o v e r , h e a d} o f t h e s o l l I v l e c h a n l c s s e c t l o n o f t h e D l v i s l o n u d e s i g n e d a n l m p r o v e 9 t y p " of water tube leve1. T h l s h a s p r o v e d s o s u c c e s s f u l _{l n u s e t h a t l t h a s b e e n thought that a r,rrrltten} r e c o r d o f l t s d e t a i l s a n d a p p l l c a t l o n m i g h t b e o f g e n e r a l s e r v l c e " _{T h l s r e p o r t p r e s e n t s s u c h a d e s c r l p t l o n o} A t t e n t l o n _{1 s d l - r e c t e d t o t h e eoneludlng note whl.ch} e x p r e s s e s t h e w L l L l n g n e s s o f t h e D l v l s i o n t o l o a n i t s o w n l n s t r u m e n t a n d t o a s s i s t w l t h s e t t l e m e n t o b s e r v a t l o n s o f l m o o r t a n t b u l l d i n g s _{i n c a n a d a w h e n f o u n d a t l o n} _{c o n d l t t o n s} s u g g e s t t h a t s l g n l f l e a n t r e s u l t s m a y b e o b t a l n e d " E a c h s u c h p t g _ d l m u s t n e c e s s a r l l y b e a l o n g - t e r m p r o j e c t b u t every b u l l d t n g _{p l a e e d under observatlon} _{w l l l} _{c o n t r L b u t e} _{s o m e i h l n g} t o u l t l m a t e u n d e r s t a n d l n g _{o f t h l s t m p o r t a n t e n g l n e e r l n g} p r o b l e m ,

0 t t a w a ,

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A NEW WATER TUBE LEVEL FOR MEASITRING

TIM

SETTLEMENT

OF BUTLDTNGS

b y F . L . P e c k o v e r S e t t l e m e n t o f b u l l d l n g s o c c u . E s h a t u r a l l y w h e n e s o l 1 s e r e t o o s o f t t o c a r r y t h e L o a d s w h l c h s t r u i t u r e s l m p o s e o n t h e m w l t h o u t d e f o r m i n g . T h l s d e f o n m a t l o n u s u a l l y t a k e s p l a e e v e t r y s l o w l y .

The soll acts somewhat Ilke a saturated sponge, and the additlon o f l o a d c a u s e s w a t e n t o s q u e e i z e out" T h l s r e d u c e s t h e v o l u n e o f t h e s o l l u n d e n t h e l o a d a n d t h e s t r o u c t u r e r r s e t t l e s r t . f f t k r l s s e t t l e m e n t w e r e u n i f o r m o v e r t h e w h o l e f o u n d a t l o n a r e a , l l t t l e

damage would result. However, lt always tends to be more pronounced ln the rnlddle of a structure than at the edges and corners, even l f t h e s o l l 1 s q u l t e u n l f o r m . U n l e s s t h e s t r u c t u r e i s r l g l d e n o u g h t o b e u n a f f e c t e d b y t h i s . u n e v e n s u p p o r t , l t l s s u b J e c t e d t o f l d l f f e r e n t l a l _{s e t t l e m e n t n} _{a n d d a n a g e u s u a l l y} _{r e s u l i s .} S e t t l e m e n t s a r e a f o u n d a t l o n p r o b l e n a - w h e r e v e r s o l l s a n e f o u n d w h l c h c o m p r e s s u n d e r l o a d . A L l c l a y s a r e s u b J e c t t o t h l s a c t l o n t o s o m e e x t e n t , t h e a m o u n t o f e o m p r e s s l o n l n c r e a s l n g w l t h t h e l r s o f t n e s s . T h e t e n d e n c y c a n b e s t b e d e t e c t e d b y l a b o n a t o n y t e s t s o n u n d l s t u r b e d s a t n p l e s o f s o l 1 o b t a l n e d f r o m b o r e h o l e s o n t h e s i t e . M e a s u r e m e n t s o f s e t t l e m e n t m a y b e t a l < e n t o a d v a n t a g e w h e n e v e r t h e d e s l g n o f a f o u n d . a t l o n l s b a s e d o n s u c h t e s t s , s l n c e t h e m e a s u r e m e n t s w t l l g l v e a p o s l t l v e c h e c k o n t h e v a l l d L t y o f t h e t e s t r e s u l t s , T h e y w t 1 l a l s o b e o f v a l u e w h e n n o t e s t n e s u l t s a r e a v a l l a b l e , b u t w h e n o b s e r v a t l o n o f n e a r b y q t r u e t u r e s o t 3 a g e n e r a l I r r o w l e d g e o f t h e s l t e l n d l c a t e s t h a t s e t t l e m e n t d a m a g e m a y o c c u r . f n s u c h a c a s e t h e y a d d t o t h e u s e f u l h r o w l e d g e o f t h e s o l I c o n e e r n e d . a n d s o l e a d t o l m p r o v e d structural d e s l g n a n d m o r e a c c u r a t e p n e d t c t l o n o f s e t t l e n r e n t s " 0 f m o r e d l n e c t l n t e r e s t t o t h e b u l l d e n l s t h e f a e t t h a t a n a c c u r a t e a n d c o n t l n u l n g r e c o r d o f

settl-ement w111 detect movements whlch are tendlng to damage a stnucture. Study of such a record w111 show the maxlmum movernent w h l c h r n a y u l t l m a t e 1 y . b e e x p e c t e d , a n d s o p o l n t o u t w h e n a n d h o w n e p a l r s c a n b e s t b e m a d e "

Methods of Measunlng BulldlnE{ Settlements

The most common method of measurlng bul1d1ng settlements l s w l t h a n e n g l n e e r t s l e v e l - a n d r o d , B y t h l s m e t h o d a s m a n y o b s e r v a t l o n p o l n t s a s p o s s l b l e a r e r e a c h e d b y a l e v e 1 s u r v e y l n a b u l l d l n g b a s e m e n t a n d r e l a t e d t o a b e n c h m a r k o u t s l d e . R e a d l n g s a r e t a k e n w l t h a p r e c l s e l e v e l o n o b s e r v a t l o n p o l n t s c o n s l s t l n g o f , s t e e l b o l t s o r b a r s w h l c h h a v e b e e n e m b e d d e , d ln t h e w a l l s a n d

c o l u m n s o f the stnucture.

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? -T h l s m e t h o d h a s b o t h g o o d a n d b a d p o i n t s . i t c a n b e d o n e w i f h s t a n d a r d e q u i p m e n t a n d lnvolves no initlal o u t l a y e x c e p t t h e l n s t a l l a t i o n o f t t r e o b s e r v a t i o n p o i n t s . f h e y , h o w e v e r o o f t e n d i . s a p p e a r o r a r e d a r n a g e d , p a r t l c u l a r l y i f i n s t a l l e d w h i i e e o n s t r u e t i o n i s s t i 1 1 g o i n g o n " M e a s u r e n e n t s b e t w e e n r o o m s a n d a r o u n d c o r n e r e a r e h a r d b o m a k e a n d a r e o f t e n i n a c c u r e t e , a n d t h e n u m b e r o f o b e e r v a t l o n p o i n t s w h l c h l t i s p o s s l b l e t o r e a c h i n s i d e a b u l l d i n g a r e o f t e n n o t e n o u g h t o y l e l d g o o d c o n t o u r s o f s e t t l e r n e n t . L e v e l l i - n g i s d o n e b y o p t i c a l m e a n s n a n d i f p a r t i t i o n w a l 1 s o r t h e e o n t e n t s o f a b u i i - d i n g p r e v e n t sightlng a s p e c l f i c p o i n t , l t m u s t b e a b a n d o n e d " T n s p J _ t e o f t h e s e d i s a d v a n t a g e s , t h l s t y p e o f o b s e r v a t i o n i s s u i c a b l e w h e n t h e c o s t o f t h e w o r k i s t h e c h i e f c o n s i d e r a t i o n " a n d w i t h c a r e i t c a n y i e l d r e a s o n a b l e r e s u l t s . T h e p i o n e e r l n p r o m o t i n g b e t t e r m e t h o d s o f m e a s u r i n g s e t t l e m e n t s _{w a s D r . K a r l T e r z a g h i ,} t h e f o u n d e r o f m o d e r n s o i l m e c h a n l c s . T n L 9 3 3 i n G e r m a n y h e p u b l i s h e d a p a p e r + i d e s c n i b l n g a s u r v e y i n g a p p a r a t u s u s l n g a l o n g t u b e f l l 1 e d w i t h w a t e r , a n d b a s e d o n t h e p r l n c l p l e t h a t w a t e r s e e k s i t s o w n l e v e I . A l t h o u g h t l a i s m e a n s o f c a r r y l n g l e v e l s h a s b e e n u s e d i n e r u d e f o r m f r o m e a r l , y h i s t o r l c a l t l m e s , T e r z a g h l w a s a p p a r e n t l y t h e f l r s t t o a d a p t i t t o c o n v e n l e n t f o r m f o r s u r v e y i n g p u r p o s e s o ' H l s o r i g l n a l a p p a r a t u s i s s t l 1 l u s e d w i t h e x c e l l e n t r e s u l t s . f t 1 s d e s l g n e d f o r f a f u " I y p r e e i s e m e a s u r e m e n t s a n d l - s t h e r e f o r e o f g r e a t e s t u s e o n l a r g e a n d e x p e n s i v e s t n u c t u r e s w h e n e t h e s m a l l e s t m o v e m e n t s a r e w o r t h y o f n o t e , 0 n b u i l d i n g s o f m o d e s t s i z e , h o w e v e r , t h e p r e c l s l - o n n e e e s s a r y t o o p e r a t e a n d r e a d t h i s i n s t r u m e n t a n d i t s i n i t l a l e x p e n s e g e n e r a l l y d i s c o u r a g e i t s u s e " T h l s 1 s u n f o r t u n a t e s l n c e s e t t l e m e n t m e a s u r e m e n t s o f t e n p a y g o o d d l v l d e n d s o n a l l b u t t h e s m a l l e s t b u l l d i n g s . f n o r d e r t o p r o r n o t e t h e w i d e r u s e o f t h l s a l d t o g o o d f o u n d a t l o n d e s l g n , a s l m p l e a d a p t a t l o n o f t h e T e r z a g h i a p p a r a t u s h a s b e e n d e s l g n e d b y t h e D i v i s l o n o f B u l l d i n g R e s e a r c h o f t h e N a t l o n a l R e s e a r c h C o u n c l l . I t w i l L b e r e f e r r e d t o l n t h i s r e p o r t a s t h e t f N . R . C . w a t e r t u b e l e v e l r t " T h l s a p p a r a t u s l s o f a l o w e r o r d e r o f p r e e i s l o n t h a n t h e o r l g l n a l , b u t h a s p r o v e d l t s e i f s u f f l c i e n t l y a e c u n a t e a n d r e l l a b I e t o m a k e g o o d l e v e l s u r v e y s . I t l s i n t e n d e d f o r u s e . w h e r e t h e m o r e p r e c L s e l n s t r u m e n t i s n o t w a r r a n t e d . T h e N . R " C . W a t e r T u b e L e v e l T h e a p p a r a t u s ( F l g " I ( a ) ) c o n s l s t s e s s e n t l a l l y o f t w o o p e n g l a s s t u b e s o f w a t e r l l n k e d b y a h o s e " f l r h e n t h e s e t w o t u b e s a r e h u n g f r o m f i x e d o b s e r v a t i o n p o l n t s , t h e w a t e n p r o v i d e s a l e v e L -l i n g m e d -l u m a n d m a k e s a c c u r a t e m e a s u r e m e n t s p o s s -l b -l e , T h . i s m e t h o d o f c a r r y l n g l e v e l s l s m o s t c o n v e n i e n t s i n c e a d i r e e t l l n e o f s i g h t l s u n n e c e s s a r y a n d c o r n e r s a n d c o l u m n s a r e t h e r e f o r e n o o b s t a b l e ; " T h i s , a l o n g w l t h t h e a e c u r a e y o f t h e m e t h o d , o v e r c o m e s m a n y of the disadvan-t a g e s o f disadvan-t h e o p disadvan-t l c a l m e t h o d " r a , ' T e r z a g h l , K . v " ( T m p r o v e d Method

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i r f V e r b e s s e r t e s f o r O b s e r v i n g

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-T h e a p p a r a t u s l s p i b t u r e d t n u s e 5 " n F l g . 1 ( b ) , T h e P n 1 n c l p 1 e u s e d l s d e s c r l b e d j - n I;'iE. 2 where the vertlcal d l s t a n c e s , d o r f n o m t h e o b s e r v a t l o n p o l n t s _{t o a s c a l e o n t h e l n s t r u m e n t} _{a r e} t h e o r e t l c a l l y _{t h e s a n e f o n b o t h t u b e s .} _{T h e v e r t l c a l} _{d l s t a n c e s ,}

d 1 a n d d 2 r b e t w e e n the scales and the fnee waten level are meaiured. T h e d L f f e - r e n c e b e t w e e n the elevatlon o f t h e t w o v e r t l c a l - p o l n t s l s therefore D - df - d2. Any error due to the dlstanee d,.., not being e q u a l o n t h e t w 6 l n s f , r u m e n t s ls cancelled out lf they ard reversed o n e a c h p a l r o f o b s e n v a t l o n p o l n t s _{a n d t h e a v e r a g e o i n e a d l n g s t a k e n .}

I t l s l n t e n e s t l n g t o n o t e t h a t t h e s a m e p r l n c l p l e o f l e v e L r l " g _{w l t h w a t e r c o n f l n e d ln a hose or plpe hal ueen applled} r e c e n t l y t o f o l l o w t h e c h a n g e s i n e l e v a t l o n o f m s n y s t r u c t u r e s o t h e r t h a n b u l l d 1 n g s . f t h a s b e e n u s e d p a r t l c u l a r l y l n e m b a n k m e n t s , r e t a l n l n g w a l l s , d a m s a n d b r l d g e s , r n t h e s e c a s e s , a s w e l l a s l n b u _ l I d i n g s ' a p e r m a n e n t p l p l n g _{s y s t e r n c a n b e l n s t a l r e d ,} _{w l t h o p e n} w e l l s _{a t p o l n t s w h e r e m e a s u r e m e n t s are to be taken.} _{S u c h a n l n s t a t} -l a t -l o n l s s l l g h t l y _{m o r e e x p e n s l v e b u t m u c h s l m p l e r t o u s e than a} p o n t a b l e water system, and may b9 kept ln mlnd where lt 1s expected t h a t 1 e v e l n e a d l n g s w111 contlnue for a long perlod" r t w 1 1 1 1 o f c o u r s e , b e s u b J o c t t o p o s s l b l e d a r n a g e d u e t o l t s e x p o s e d l o c a t l o n .

A n y p r e c l s e l e v e 1 s u r v e y l s n o t e f f e c t t v e u n l e s s u s e d w l t h r e l - i a b l e o b s e n v a t l o n p o l n t s . _{T o o v e r c o m e t h e d l f f l c u l t y} _{o f} h a v l n g p o l n t s _{d a m a g e d o r r e r n o v e d . , T e r z a g h l used a removable wall} p l u g w h l c h fltted l n t o a r e c e s s e d s o c k e t l n the bulldtng w a l l . T h e

s o c k e t w a s c o v e r e d b e t w e e n r e a d l n g s . T h l s t y p e o f o b s e r v a t l o n p o l n t i s a l s o u s e d w l t h t h e N . R . c . w a t e n t u b e l e v e ] , _{a n d l s s h o w n l n F l g " l .} r n c o m b l n a t l o n t 1 ! ! _{_ a _ g o o d b e n c h m a r k r t h e s e p o i n t s} _{a r e f o u r r d t o g l v e l o n g a n d} r e l l a b l e s e r v l c e " A c c u r a c y a n d Llmltatlon o f t h e W a t e r T u b e f , e v e 1

I t l s u s e f u l t o c o m p a r e the accuracy of the N.R"C. water t u b e l e v e l w l t h t h a t o b t a l n a b l e b y a n e n g l n e e r f s l e v e l a n d r o d . T h l s c o m p a r l s o n , a l o n g wlth that of costl w111 asslst 1n showlng when the use of the speclal appanatus ls warnanted.

A n e n g l n e e r r s L e v e l l s u s u a l l y r e a d t o 0 . 0 0 I f e e t ( 0 . 0 1 2 l n c h e s ) i n p r e c l s e w o r k . T h l s m 6 a n s t h a t t h e e l e v a t l o n o f a n y p o i n t _{l n a c l o s e d s u r v e y w l t h thls lnstrument w111 be for.rrd} w l t h l n a b o u t O . O 2 5 l n c h e s u n d e n t h e condltlons u s u a l l y p r e v a l l l n g l n a b u l l d l n g b a s e m e n t . T h e w a t e n t u b e l e v e l l s r e a d t o 0 . 0 0 5 l n c h e s " f t h a s b e e n f o u n d f r o m m a n y s u r v e y s wlth the apparatus that ln a closed survey t h e e r r o r l n f l n d l n g t h e e l e v a t l o n o f a p o l n t w l l l h a r d l y e v e r e x c e e d 0 . 0 0 6 l n c h e s a n d l s u s u a l l y L e s s t h a n o . o o 3 L n c h e i .

(9)

l +

-T h l s degree of accunacy r.s enough to folrow early tnends

l n the dlffereltr6r

_{r n o v e t " " 1 or 6uiiar"g".}

D e t e c t l o n of the ovenall

movement of bu_lldlngs ls qurte r"a"p"io'8"t of thls, and depend.s

_{t h e u s e o f p r o p e r bdnch t*ok".}

on

t i r r t " - i ; - d l s c u s s e d ln a rater section"

U s e of Water Tube Level

the apparatus _{on an obsenvatlon} _polnt _{or war.l} rre a means of suspendlng it so that the

; t o t h e s c a r - e r s always constant, * " * a J u s t a b l e t h e w a l 1 at the lower end to keep it ln"a- -. a 1 e v e l bubble-. I t _{l s a n a a v a n t a g e to be}

r a t u s _ ln posltlon _{o n a w a l l p l u g so that al_I} t o o b t a l n l n g _{a g o o d readlngl} _{a n O t h i s is}

s cre

w cl amp

use

_{d to 1i*tr.j" lJi i rll" ;;"x" r: l;l "::}

-ffi

_Jlirhorl

zont

al

ll

T h e g l a s s tube ln whlch the water level 1s read is held

between two ftfttngs

_{*rti"rr fonn t;t-oi}

_{trr" frame ;i the appanatus"}

B y loosenLne two rl"ntea-""r.*s

_{L h " tube may be removed for per-lodlc}

c l e a n l n g '

l ' l a t e r

" u " " f i " t

i r r " tube

_{" t r a - i "}

c o n t r o l l e d by a stopcock

a t the bottom of the lnstnument, to whlch a long flnm hose of

! : g t p 3 " e n t

p l a s t l c

l s

" o n t r " c t e d ,

l e a d l n g to the othen end of the

a p p a r a t u s .

* _ ? l a q a n y

g . a r d e n 116se-i"-rno"" economlcal, but is not

n e c o m m e n d e d

_{s l n c e alr Lu6Ules}

" r r r r r o t - U *

s e e n r &nd their escape durlng

n e a d l n g s would affect the accuracy of the survey.

The helght of the column of,, waten ls measured by a vernier

a n d s c a L e ' ( T h l s - f o l 1 o w s a suggestlon obtalned f;;;-professor

_{R . r r .}

D a w s o n of the Unive.;iat-of

_{T e i E ; , i--irr" vernler is camled oh a}

l e s over the- glass tube and-is h;ld i"-;t

L s p r l n g .

_{T h e s c a l e I s r l g f a f y connected to}

r t u s .

_{A t the sane t!me, t6e s6ale is}

" , r [ p o * t u a

r s t o allow the vernier to be adJusted ;iih

; as much 1l-ght as posslble f all

- o n

t h e Elass

,fii|ru;tr;"Tli:i. tn" glass

tube rs pari[eJ

r n n e a d l n g , t h e rneta] sleeve 1s ralsed so that lts top

e d g e j u s t touches t[6 uoitom of the *"rriscus ln the tube. Readlnns

may be taken to the nearest o.ooi--rrr"rr'i"..thl_s way. rfi; i;';;TX'

w a y of measurlng the levei of a water surface.

s l m p l e

T a X r _ a n d i t s * " " , r " * " y - i "

q u l t e l n

e r r o r s lnvolved ln a survey such as thi;"

I y deslrabre ln the case oi targe uurrJings

ay tlI?lve

costly-repalrs.

_ih"

"corrorrry

and

- l n e E n o d recommends tt for average coieattl.ns"

D e t a l l e d lnstructlons

_{f o r the assembly of the water tube}

l e v e I ane ccnflned to apferrafx e.

(10)

' 2

Obsenvatlon Polnts and Beneh i/iarks

T h e o b s e r v a t l o n p o l n t s _{u s e d w l t h t h e N . R " o . water tube} l e v e l a r e d e t a l l e d a n d l l l u s t r a t e d _{1 n F l g . l, and a convenlent}

n e t h o d f o r i n s t a l l l n g _{t h e m l s d e s c n l b e d l n A p p e n d i : c B,} _{W h e n s u r v e y e d} r y l t h - c a r e , t h e e l e v a t l o n o f t h e s e p o l n t s a l o i r L w 1 l I s h o w a n y tlltlng, d l s h l n g o r d i f f e r e n t l a l _{h e a v i n g r n o i l o n o f a bullding.} _{T o d l t e c t} t h e m o v e m e n t o f the bullding _{a i a w h o l e , h o w e v e r , lE ls necessary} t o f l n d t h e l n e l e v a t l o n r e l a t l v e _{t o a f i x e d p o l n [ o r b e n c h m a r k "}

A n a c c u r a t e b e n c h nar"k ls therefore & n e s s e n t i a l _{p a r t o f} a n y b u l l d 1 n g l e v e l - s u r v e y , f o r w l t h o u t i t a l l o t h e r r e c o r d s a r e 1 1 m l t e 9 b y l a c k of lnfornatlon _{a s t o w h e t h e r the bulldlng} _{l s r l s l n g} o n - f a 1 1 1 n g . _{r b g r t h e p o t n t of vlew cf checklng a deslgnl thls} lnformatlon _{ls fu1ly} _{as useful} _{as a knowledge of the alfierentlal} movement of the structure"

T h e l n t e r l o r r e v e l s u r v e y l s u s u a l l y t i e d l n w l t h a n

o u t s l d e b e n c h nark by lnstalllng t w o o b s e r v a t i o n p o l n t s _{a t c o n v e n l e n t} P l a c e s r o n e o n t h e l n s l d e a n d o n e o n the outsl-de bf tfre butldlng"

T h e _ ln n e r p o t n t _{l s t h e n a p a n t o f the regular} _{i n t e r i o n} _{i e v e l} _{* u i v e y ,} w h l l e t h e o u t e n - p o l n t , _{w h l t t r 1 s s u b J e c t t o t h e s a m e ehanges ln}

e l e v a t l o n , _{c a n b e c h e c k e d a g a l n s t tfie bench rrark o}

e a s 1 1 y f o u n d . I n f a c t , m a n y r e l l a b l e h a v e l a t e r h a d t o b e

,Til: ffl;::"*o"r.il,'ff

_{|lffil',",.,t}

{ a s l n s t a l l e d s l n c e e x t r e m e

a c c u r a c y w a s n o t r e q u l n e d . _ I t _ w a s t h o u g h t s u f f l c l e n t t o u s e n e a r b y s t r u c t u r e s _{w h l e h l / r e r e fairly} _{o l d . a n d p r e s u m a b l y s t a b l e .} _{T w o b e n c h} manks were chosen, therefore, _{one on a large hoirse wlth a dee.o} b a s e m e n t , arrd the other on a hydrant, slnce the waten malns in this I o c a t l o n _{r a n a t a d e p t h of I feet"}

S l n c e t h e n , the differentlal m o v e m e n t o f t h e t w o b e n c h m a r k s a l o n e h ? r - b e e n nearly half an inch, and thls motlon ls qulte

l n r e g u l a r . I t 1 s l r o n l c a l - _{t o f l n d t h a t t h e m o v e m e n t of the bench} m a r k s r e l a t i v e _{t o e a c h o t h e r h a s b e e n conslderably} _{g r e a t e r} _{t h a n t h e} m o v e r n e n t o f t h e new buildlng r e l a t l v e t o e l t h e r ;

T h e b e s t b e n c h marks are those on.bulldlngs w h l c h a r e f o u n d e d . o n r o c k . _{T h e s e enable the settlement of}

" n ! t " a n b y

s t r u c t u r e _{t o b e t n a c e d wlth confidence.} _{B e n c h m a r k s on builalngs} f o u n d e d w e l l - b e l o w the 1evel to whlch solls move seasonally rne"

a l s o a c - c e p t a b l e ' S e a s o n a l swelling a n d s h r l n k l n g o f c l a y i o l l s a r e c a u s e a Py varlatlons l n n o l s t u r e c o n d l t l o n s a n d S f r r t n k " g 6 m a y b e p a r t l c u l a r l y _{p r o n o u n c e d when tree roots are present"} _{T E e t w 6} b e n c h m a r k s mentloned above were nade uselesi Uy such seasonal e f f e c t s . _{F L n e n o o t s a n d cracks are sometlmes f6und ln solls} _{a t ,} d e p t h s o f 1 0 o r 1 2 f e e t . A b u l l d l n g _{o n w h l c h a b e n c h m a r k l s t o b e} p r a c e d should, therefore, _{b e f o u n d e d . a t that depth or greater.}

(11)

6

-W h e n a b e n c h mark ls placed on an exleiing b u l l d l n g v r h l c h ls not founded on rock, one must be sure that lb ls-far

"nou[h a]ray f r o m t h e t - , e r , r s t r u c t u r e _{t o b e u n a f f e c t e d} _{b y l t s s u b s l u e n c e "} _{i f r f s} c a 1 l s f o r Judgment ln each casee but a mlnlmum dlstance of at Least t w l c e t h e w l d t h o f the ner+ bullding 1 s s u g g e s t e d l f t h e s l t e l s u n d e r L a l n b y a d e e p layer of conrpnesslble-so11. I f a d l s t a n c e o f o v e r 1 0 O f e e t l s l n v o l v e d , l t l s a d v l s a b l e t o h c i v e l n t e n m e d l a t e p o l n t s o f o b s e r v a t l o n "

Deep Benc,h Manks

I f n o e x l s t l n g s t n u c t u n e c a n b e u s e d f o r the loeatlon o f e b e n c h m a r k , a s p e c l a l l n s t a l l a t l o n c a n b e r n a d e q u l t e e c o n o r n l c a l l y . V t r h a t l s e s s e n t l a l l y _{n e c e s s a r y l s a r e f e r e n c e p o i n t supported at a} p o l n t _{l n t h e g r o u n d w h l c h w111 not moveo A slmple design for such}

a bench mark ls shown ln Fig, [, and t]r1s ls mahe up of parts whlch a r e - e a s l l y a v a l l a b l e . F l r s t c h o o s e t h e d e p t h a t whlch the bench m a r k l s t o b e founded and then the plpe secttons nay be precut m a k l n g t h e l n s t a L l a t l o n a s c o n v e n l e n t - a s p o s s l b l e . T h l s t y p o o f b e n c h m a n k m a y be sultably l n s t a l l e d _{1 n o n e o f t h e t e s t U o i ' 6 h o l e s} u s e d t o e x p l o r e t h e b u l l d l n g _{s l t e "} I f s u c h a r e f e n e n c e p o l n t l s t o b e c l o s e t o o r l n t h e b u l l d l n g _{b e l n g m e a s u r e d - - a n d t h l s l s m o s t c o n v e n L e n t - * t h e n l t m u s t} b e c a r r l e d t o b e d r o c k , s l n c e a l l t h e l n t e r v e n l n g s o i l l a y e r s w 1 1 1 d e f o r r n t o s o m e e x t e n t und.er the load of the Uullding. f i ' b e d r o c k l s t o o d e e p , t h e n thls bench mark sliould be at a hoilzonfal d l s t a n c e of et least l-00 feet away from the bdlldlng to be out of the zone o f a f f e c t e d s o l I . _{A n y b e n c h m a n k whlch does not extend t,o bednock} r n u s t b e c a r r i e d _{d o w n r o e I l b e l o w a n y s u n f a c e effects} _{l n t h e s o i l p} s u c h a s t h o s e c a u s e d b y t r e e s , t o a d e p t h o f a t l e a s t 30 feet aia p r e f e r a b l y _{a s d e e p a s p o s s l b l e .}

I f t h e b e n c h mark can be put lnslde the bulldlng, f o n l n s t a n c e _{i n a c o v e r e d w e l l l n the basement floor,} _{l t m a y 6 e u s e d .} w l t h a m i n l m u m o f lnconvenlence _{a n d a m a x l m u m o f a c c u r a c y , a l t h o u g h} l t w 1 ] 1 b e m o r e e x p e n s l v e t o l n s t a I I " f t l s n o t u s u a l l y d e s l r a b l e t o t l e a n o u t d o o r b e n c h m a r k t o a s e n L e s o f l n d o o r l e v e L s w l t h t h e w a t e r t u b e L e v e l . A g o o d . e n g l n e e r t s l e v e l l s m o r e s a t l s f a c t o r y _{s l n c e 1 t l s n o t a f f e e t e d s o} - q u c h b y d l f f e r e n c e s l n t e m p e r a t u r e a n d o t h e r outdoor effects" I , J l t h c a r e lt w111 glve sufilclent a c c u r a c y " T h e L e v e l S u r v e y a n d f t s R e s u l t s I n a n e w b u l l d l n g , t h e f l r s t l e v e l s u r v e y s h o u l d b e t a k e n a s s o o n a s c o n s t n u c t l o n o p e r a t l o n s w 1 1 1 p e r m l t , i f t h e r n e a s u r e n e n t g a r e t o b e o f m a x l m u m v a l u e later o n . O b s e r v a t i o n p o i n t s a r r e u s u a l l y p l a c e d a s s o o n as the forms have been stnlpped fnolu the basement

c o l u m n s " T h e n , e v e n while bul1dlng materlals a n d o t h e r o b s t r u c t i o n s a r e s t r e w n a r o u n d r -the flrst s u r v e y c a n b e m a d e to establlsh t h e t t l n l t l a l

e L e v a t i o n t t o f a l l observailon p o l n t s l n t h e b u l r d l n g , a g a l n s t w h l c h a l l f u t u r e s u r v e y s a r e c h e c k e d " o f c o u r s e , t h ;

(12)

4 - t

s t n u c t u r e _{w 1 1 1 u n d e r g o s o m e movement even befone this ttme, but the} amount of thls must remaln unknorrn, and the levels found ln thls f l n s t s u r v e y m u s t s e r v e as the orlgln o f a l l s u b s e q u e n t s e t t l e m e n t c u r v e s . I t l s l m p o r t a n t , t h e r e f q r e , t o o b t a l n t h e s e r e c o n d s e a r l y l n t h e l i f e o f t h e b u l l d l n g .

D e t a l l s _{o f e q u l p m e n t a n d t h e p r o c e d u r e used ln carrylng} o u t a l e v e 1 survey are glven ln Appendlx C, and a sultable foi'm ior n e - c o n d l n g t h e r e s u l t s o f a s u n v e y l s s h o m , r , w t t h s a m p l e flgures, l n T a b l e 1 ' W h e n t h e elevatlons o f a l l . s t a t i o n s a r e t o i r n a a n d . e n t e r e d l n t h e t a b l - e , these are compared wlth sets of elevatlons f o u n d i n p r e v l o u s s u r v e y s . _{T h e s o c o m p a r l s o n s g l v e the total} _{a m o u n t a n d r a t e} o f s e t t l - e ! ' n e n t o f all points i n t h e U u l l a t n g .

T h e c l e a r e s t _{a n d s l r n p l e s t means of showlng the dlstrlbutlon} o f s u b s l d e n c e ln a structure i i b y m e a n s o f c o n t o u r i o f e q u a l

s e t t l e m e n t " _{A n e x a m p l e o f t h l s type of presentatlon} _{l s g i v e n i n} F l g . 5 | Slnce the distrlbutlon o i - s e t t l b r n e n t w 1 1 1 p r o U a 6 l y change w l t h t 1 m e , 7 t l s u s u a l l y n e c e s s a r y t o ' d r a w s u c h s e t t l e m e n t p l a n s for t w o o r t h r e e d l f f e n e n t _{s t a g e s o f t h e m o v e m e n t .} I f a p l c t u r e _{o f t h e r a t e o f s u b s l d e n c e l s d e s l r e d ,} p a r t l c u l a r l y _ _{l f s u r v e y s a r e m a d . e a s b u l l d l n g} _{c o n s t r u c t i o n} _{p r o c e e d s ,} l t - l s - h e l p f u 1 _{t o p l o t t h e s e t t l e m e n t o f r e p i e s e n t a t l v e} _{p o f i r t s b e L o w} a h o r l z o n t a l _{t l m e a x i s a n d t h e i n c r e a s e ln bulldlng} _{l o a d a b o v e} t h l s a x l s . _{T h l s t y p e o f p l o t 1 s s h o w n ln Fi-g. 6.} _{T h e p r o g r e s s} o f t h e s e t t l e m e n t c a n t h u s b e f o 1 1 o w e d , and an experlen-ced person can predlct _{ln advance from the shape of the curve the course of} t h e s e t t l e m e n t w l t h t l m e .

f f t h e p r o J e c t r e c o r d s a r e t o b e c o m p l e t e , t o t h e s e g n a p h s s h o u l d be added a simple key plan to shbr^r the Locatlon of o b s e r v a t l o n p o l n t s , _{b e n c h m a r k s , t e s t b o r l n g s ,} _{a n d t h e b u i l d l n g} f o u n d a t l o n _{w l t h u n l t l o a d s f o r the main aneds, a typlcal} _{g * o u n d} c r o s s - s e c t l o n _{s h o w l n g s o 1 1 p r o f l l e} _{a n d c o n d e n s e d t e s t b o r l n g}

r e c o r d s , _{a n d a f e w p a g e s of text summarlzLng all field} _{o b s e i v a t l o n s} a n d t e s t s , C o n c lu s l o n T h e D l v l s l o n _{o f B u l 1 d l n g R e s e a r c h o f t h e N a t l o n a l R e s e a r c h} C o u n c l l 1 s l n t e r e s t e d l n p r o m o t l n f t h e u s e o f b u L l d l n g s e t t l e m e n t s u r v e y s 1 n C a n a d a wherever results m a y b e c f g e n e r a l l n t e r e s t . I t w 1 1 1 , t h e r e f o r e , b e g l a d t o c o n t a c t anyone eontemplatlng s u c h w o r k , a n d t o a s s l s t l n t h e p l a n n l n g _{a n d a c t u a l t a k l n g o f the surveys.} $ u r v e y o b s e r v a t i o n p o l n t s _{a r e a v a l l a b l e} _{f o r f n J t a l 1 a t i o n o} _{a n 6 . a} w a t e n t u b e l e v e l m a y b e b o n r o w e d for use unden supervlslon o f a m e m b e r o f t h e D l v l s l o n a l s t a f f . T h e o n l y c o h d l t l b n f o r s u c h s e r v l c e l s t h a t d e t a l l s o f s t r u c t u r a l d e s l g n a n d a n y s o l l t e s t s L n v o 1 v e d , a n d r e s u l t s o f l e v e 1 s u r v e y s b e m a d e a v a l l a b l e t o t h e D l v i s l o n , a f t e r c o n s u l t a t i o n r ^ r l t h t h o s e r e s p o n s l b l e "

(13)

I

C . weter tube Level may also b€

ida who ereo genu!.nely lntorested.

rfonnod whenever a level of thls

r only ln thls nay that the dostgn

correspondence should. be addnessed

ng Reseanch, $atlonal neeearch

(14)

P t .

N o . LeveIN o . Plug No. Rdg.( In. )

TABTB 1

Reoord of Settlernent Sunvev Dlff. Level RdA. Dlff.

( r n . )

N o .

( r ; . )

( r n . )

Avenage D l f f . Conrected D i f f . Elevatlon( I n . )

6.zLO

v - - E o v f v

r

2 r

8.0115

2 0 . 0 0

Bulldlng. rrltl P a r t y : h l . R . S . , F . L . P . D a t e : _{3 1 O c t . 1 9 5 1 .}

Calcu1atlon of closune connectlon:

IgEg.: It ls asaumed that the elevatlon of Pt. I ls found to be 2O.OO ln. by neeEurement from a bench mark.

Sum

Sun of + dlfferencelt of - dlfferences = -11.160 ln.= +11.156 ln.

olosune srror

= TT.-6TC[il

Indlvldual closure oonnectloD = rO.006 =

- 0 . 0 0 1 ln. pen polnt.

(15)

U P P E P F L A N G E S C R E W S C A L E S U P P O C T S L O W E E F L A N 6 E C L A M P F C A M E UPPLz V E P N I E P s L r o r N 6 FLAN6E S C A L E S L E E V E P L A S T I C T U B I N G F l G U R E | ( o ) C O M P O N E N T S O F W A T E R T U S E \ o.^r" T U B E L E V E L s T o P c o c K S C R E W LOWE P B t r A C K E T F I G U R E I ( b )

PHOTOGRAPH OF WATER TUBS LEVEL L E V E L

(16)

d, AND d " : coNsTANT d 2 : V A R , / A 6 L E S

D :

d r - 4 "

PlFFEAENCE / N E L E v A T t o N / A N P 2 . of PotNTs

FIGURE

P R I N c I P L E

o f

w A T E R

T U B E

L E V E L

O . d . A . T E C H N I C A L R E P O R T N O . I I

(17)

S O C K L T K E Y F O F I S O C K E T

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P L A S T e R o f P A R r s P O I N T P R . O T L C T I V E W A L L P L U 6

C O V E R

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( e )

o B S E R V A T T o N

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(c)

A S S E M B L Y

F I G U R L

3

P O I N T W A L L O B S E R , V A T I O N D . b . R . T E C H N I C A L R E P O R T N O . T T

(18)

GROUND LINE DATUM LEVEL 4" COUI{TERSUNK P L U G G A L V . I R O N I G A L V . I R O N SPACE BETWEEN P I P E , C O U P L E D I N S E C T I O N S . P I P E , c O U P L . E D t N S E C T | O N 3 . PIPES FILLED WITH HEAVY

o t L .

1 . P I P E F L A N G E . . , ) / z S T E E L B A L L 4 ' c A L v . l R o N P t p E , 3 ' L o N G . t ' F L o o R F L A N G E , R E s r t N o o N C E N T E R I N G S C R E W S .

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F I G .

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(19)

+ l o autLDtNe "b", 6 MzNTHS coNToLttt t tTERVAL tS o. I

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.+|lXtMuM _{SEf TLEMENT}

F I 6 U R E

6 3

(20)

, '

Appendlx A

ASSE}tsLY OF WATER TUBE LEVET

f t l s s o m e t i m e s n e c e s s a r y to take apart the water tube

l e v e 1 f o r c l e a n l n g o r o t h e r p u r p o s e s , I t s r e - a s s e m b l y e a l l s f o r

sone care Lf the apparatus ls to work depencabLy. s',,eps whlch

r e q u i n e p a r t l c u l - a n a t t e n t j . o n a n e m e n t l s n e d b e L s w " f n r e f e r r l n g

t o p a r t s , _{t h e n a n e s l n F l g " I ( a ) a r e u s e d .}

( a ) P r e l l m l n a n y

f t l s a d V i s a b l e to mark all metal parts of a water tube

level _{wlth one or two pr.rnched dots to show tb whlch end. of the}

!-o"" they belong" Thls ensunes that they are always assembled. ln

the same way.

f f t h e s t o p c o e k l s o f a dlfferent m e t a l t h a n t h e l o w e r

b r a c k e t , _{1 t l s a d v l s a b l e t o c o a t t h e l n s l d e o f t h l s b r a c k e t w L t h a}

w a t e n p r o o f p a l n t b e f o r e assembly to reduce the posslblllty o f

g a l v a n l c _{a c t l o n w h e n t h e level is f11led wlth water,}

( b ) G l a s s t u b l n s

L o w - p r e s s u r e b o l 1 e r - g a u g e g l a s s e s , _{1 l n e h l n d l a r n e t e : ' s n d}

1 2 - L n c h e s l o n g , a r e satlsf actory"- E a c h g l a s s t u b e l s p r o v l d e d wlth

r u b b e r " g a s k e t s a t each end and a paeklng of sultable materlal { s u c h

as ordlnery _{rubber bands) around the lourer end"} _{Befone thts packlng}

l s l n s t a l l e d , _{t h e t u b e , w l t h t h e m e t a l s l e e v e a n d g a s k e t s i n ilacen}

ew whlle the upper flange screw

e p a c k l n g l s t h e n p r e s s e d l n t o e w t l g h t e n e d t o m a k e a w a t e r t l g h t

e r f l a n g e s c r e w w t l 1 k e e p w a t e n

( c ) P 1 a s t l c t u b l n g a n d d l s t l l l e d . water

R u b b e r o r p l a s t l e _{t u b i p g w l t h a f i r m w a L l , s l m l l a n to}

g a r d e n h o s e , should be used. S u c h a t u b e k e e p s ! . t s s h a p e a n d . volume

r e a s o n a b l y well and allows falrly f r e e m o v e m e n t , o f t h e w a t e r , e v e n

w h e n a c c l d e n t a l l y k l n k e d " T r a n s p a r o n t t u b l n g , a l t h o u g h e o m p a r a t l v e l y

e x p e n s l v e , _{l s b e s t f o r t h e p u r p o s e slnce by trrts meani arl Lrr}

b u b b l e s may be seen and removed. T h e t u b e - s h o u l d h a v e a n l n s l d e

dlameter of at l-east 5/B-lnch wlth a l/B-lneh wa1lo A length of

7 5 t e e t l s s u g g e s t e d , r w h i c h w l L r a l r o w o b s e n v a t l o n p o l n t s f o b e

s p a g e d u p t o 6 0 feet apart" r f t h e h o s e l s l o r r g e n irran thls,

o s c l l l a t l o n s _{o f t h e w a t e r b e f o r e each readlng nttt} _{t a k e a l o n g t l m e} t o d 1 9 o g t ; l f s h o r t e r t h a n t h i s r t h e d l s t a n e e b e t w e e n p o l n t s - l s r e s t r l c t l v e ' _{r f t w o p l e c e s r n u s t b e u s e d e n d t o e n d . , t h e y c a n b e} J o l n e d w i t h s t a n d a n d g a r d e n h c s e c o u p l l n g s " , L a r g e v o l u m e g a s s t o p c o c k s ' a r e s u - l t a b l e . T h e o u t l o t o f e a c h s t o p c o e k L s g n e a s e d o n t h e o u t s l d e b e f o r e t h e t u b l n g i s c o n n e c t e d , t o g u a r d against any posslble ehemleal actlon-between

t h e t w o m a t e r l a l s l n c o n t a c t " T t i e l n s l d e o f t h a s t o p c o e k s h o u l d ,

h o w e v e r , b e thoroughly _{e l e a n s e d o f a n y g r e a s e b e f o n e u s e to avold}

t h e f o r m a t l o n o f a n o 1 1 y f l l - m o n t h e water surfaee. T h e t u b l n g l s

(21)

A A

H - / _

The lnstnuments are then hung with the tubirrg on the floor,

f l u s h e d throughout wlth clean tap watei and dralned. Dtstttleo or

c l e a n tap water ls poured ln one lnstrurrent untll the tubing-tJ iuff.

Then, aften nrost of the entrapped alr b,ubblas are removed, ttre

a p p a r a t u s ls cotrnected to a vacuum pump and the water de-atr.ed by

v a c u u m fon a few hours, or preferably bvernlght.

f f the connectlons

a l e tlght the-vacu-u1_may

_{b e - n a L n t a l n 6 a simpl! by closlng the}

s t o p c o c k s " A l r b u b b l e s are n4olt uas1ly removed-from th5 hose by

startlng

_{mldway between the end.s and m-anlpulatlng q small loop 6f}

h o - s e in the hands, us1n6 large bubbles to gathen-smarl ones.

F ' t n a l l y , add enorigh de-alred water to brlng the level

r n l d w a y - u p ln the-glass tubei.

A f t e r croslng the sCofr"ocr<s

a n d

r e p l a c l n g the rubber stoppers, the apparatuE is ready for use.

( d ) fnsulatlon of tublng

The most common source of ennor ln a survey wlth thts

lnstrument ls a dlffenence ln tempgraturer arld hence-fn Aensiiy, of

the water ln the two vertlcal

por"ilons of the tube,

Thls ls aimost

c e n t a l n to occur lf one of the potnts ln the sunvey ls in a cold

stonage or furnace room. It can also be tnoublesoire, howevor,r und.er

I a g a l n s t such temperature changes,

3 v e r t l c a l l y

d u r l n g readlngs are

'"1

_{il" i;uffi}

Jiffi ;:3?:";'T,1+

""

t ls also advlsab1e when surveylng

ln places whlch are warmer or cooler than average, to leave the level

l n s u c h p l a c e s f o r a s s h o r t a tlme as posslble"

(22)

Appendix B

OBSERVATION POIi\TS

T h e o b s e r v a t l o n p o i n t s u s e d w i t h t h e N . R . C . w a t e n t u b e

level _{are shotm ln Figs. I and [.} _{A smal]. metal socket ls permanently} lnstalled ln a basement walI or column where the level ts rbqulred. I t s s o v e n r w h l c h f l t s ' f 1 u s h w l t h t h e s u r f a c e o f t h e w a l l f i n l s h , l s s t a m p e d w l t h t h e number of the observatLon station" T o t a k e a r e a d l n g , _{t h e c o v e r l s r e m o v e d w l t h a key and replaeed wlth a plug} w h l c h s e a t s f l r m l y i n t h e s o c k e t " T h e L o v e l h a n g s f r o m a g r o o v e - l n t h l s p l u g .

T h e s e o b s e r v a t l o n p o i n t s must be located and lnstal1ed w l t h g a r e t o y l e l d a c c u r a t e 1 e v e l s u r v e y s , T h e s e o p e r a t l o n s a r e d e s c r l b e d b e l o w .

( a ) C h o l c e o f l o c a t l o n

I t 1 s b e s t t o l o c a t e a l l observation p o l n t s i . n t h e l n t e n l o n o f a b u l l d l n g 1 n w a l l s , c o l u m n s o r o t h e r p a r t s o f t h e p e r m a n e n t

structure" _{They should be arranged to glve a unlfonm coverage of} t h e f o u n d a t l o n a r e a , a n d s o t h a t a c l o s e d t n a v e r s e m a y b e m a d e o f as F a n y o f t h e p o l n t s a s p o s s l b l e . D e p e n d l n g o n t h e n l g t d l t y o f t h e b u 1 I d l n g , _{l t l s a d v l s a b l e t o p r o v l d e a point for every 5oo square} f e e t o f f l o o r s p a c e o n l e s s . O f c o u r s e , t h e p o l n t s s h o u l d b e p l a c e d s o t h a t t h e y m a y e a s l I y be reached at all tlmes durlng the

c o n s t n u c t l o n a n d e a r l y l l f e o f t h e b u l l d l n g c : I f _{a b o u t 2 5 t o lO per cent of the polnts are located in} l n t e r l o r _{r + a L l s o r c o l u m n s and the remalnder ln exterlor} _{w a 1 1 s , a} falrly accurate plcture of the change ln revel over the whole f o u n d a t l o n a r e a w 1 1 1 r e s u l t .

( b ) C h o l c e o f e l - e v a t i o n

T h e o b s e r v a t l o n p o l n t s _{s h o u l d b e i n one orr'more groups, each} p o l n t _{l n a g r o u p b e l n g a t approxlmately} _{t h e s a m e e l e v a t l o n l} _{s h c 6}

t h e w a t e r t u b e l e v e l w111 only take dlfferentlal r e a d . l n g s o f a f e w l n c h e s . _{A t a n y b o u n d a r y between such groups, two polnts should be} m o u n t e d a t t h e s a m e locatlon, o n e a b o v e t h e o t h e n , s o t h a t l t w 1 1 1 b e p o s s l b l e _{t o l e v e l f r o m o n e g r o u p t o t h e o t h e r " b y d l n e c t}

m e a s u r e m e n t .

T h e b e s t h e t g h t f o n a b o v e t h e f I o o r , a n d a d J a c e n t helght _{by more than 9 lnches.} ( c ) f n s t a l l a t l o n

t h e p o l n t s is about 5 feet 6 inches

p o l n t s should not be dlfferent

l n

B e f o r e s t a r t l n g t o l n s t a l l a n y w a I 1 s o c k e t s , l t l s w e l l t o m a r k a n d n u m b e r all locatlons c l e a n l y w l t h c h a l k . f f t h e l e v e l o f t h e f l o o r o r c e l l l n g _{o f t h e b a s e m e n t l s k n o w n f r o m t h e b u l l d t n g} p l a n s r _{a m e a s u r l n g tape can be used to flnd the socket elevatlonsl}

(23)

B * 2

H o l e s f o n t h e w a l ] s o c k e t s c o n c n e t e d r l l l b l t , h e l d c a n e f u l l y 1 n h o l e a p p r o x i m a t e l y _{2 l n c h e s d e e p , t o} fr"om the face of the wa1l about I/$

may then be rnd"de wlth a 3/!-inch a l e v e 1 p o s l t l o n " D r i l l e a c h a 1 l o w t h e s o c k e t t o b e s e t l n lnch"

After each hole 1s blor^rn out wlth a small pleee of rubber

t t l b _ l n g and molstened wlth water, a wall soeket ls cemented ln place

w l t h p r a s t e r of Parls, preferably of a hlgh qual.lty, fast settlng

t ] I P e r such as dentistt s lnpresslon plasten.

f t ls- advlsable bef ore

startlngt

_{-to f lnd the sett!.ng tlme of thls plaster by mi.xlng some fui}

a d l s h wlth water"

T h e b e s t s e t t l - n g tLme ls about 1d rnlnutes; the

s e t t l n g tlme can be retarded lf necessary by addlng a smal1 amount of

anlmal gJ.ue to the rnlxlng water.

A f t e r a s m a l l a n o u n t c f t h e p l a s t e r l s m { x e c i t o f o r m a

s m o o t h l y flow!-ng paste; lntrude thls mlxture lnto the drllled,hoLe.

R e p l a c e the cover of a socket wj"th a wal1 p1ug, loosely scnewed i-nto

p o s i t i o n "

_{S m e a n more plaster cver the roughened surfaee of the}

s o c k e t .

_{T h e n by means of the waI1 plug, push the. socket lnto tiie}

d r l l I e d

_{h o l e , squee.ztng out the excess-pJ-aster, r.rnt11 the outer end}

o f the socket ls l/16 lnch behlnd the faee of the wall-" Durlng thls

o p e r a t l o n ' make sure that the wall pllrg ls held horlzontally

a [ ali

t l m e s o A snal1 hand letr'el w111 asslst in thls.

W h e n the plaster has begun to harden, the plug ls unscrowed

a n d any excess plaster removed from around and lnslde t[e socket.

T h e s o c k e t cover ls replaced and, when the plaster has completely

s e t , t h e o b s e r v a t l o n p o l n t i s n e a d y f o r u s e n

(24)

Appendlx C

CO1IDUCTING A LEVEL SIMVEY

A s u r v e y w l t h t h e w a t e r t u b e level ls nafurally m a d e l n m u c h t h e s a m e w a y a s a s u r v e y with an englneert s Ievel. r n t h e f o r m e n t h e l n s t r u m e n t _{l s f l x e d} _{t o t w o s u c c e s s l v e s t a t l o n s} _{1 n t h e} q':lrvey rather than set up between them" The operatlons are not d l f f l c u l t _{o n c e a s u r v e y i n g technlque has been acqulred.} _{r t l s} h e l p f u l , _{h o w e v e r , i f n e a d l n g s are taken on two polnts whlch are} l n t e r v l s l b l e u n t l l t h e s u r v e y p a r t y i s f a m l l l a r - w l t h l t s d u t l e s . T h e n e g u r a r s u r v e y can then proceed with l-ess chance of d.eIay. T w o e x p e r l - e n c e d men ean survey 20 to 30 polnts and calculate- thelr n e s u l t s i n a d a y "

Before beglnnlng a survey, the order 1n whlch polnts are t o b e m e a s t r e d s h o u l d be determLned" _{A s m a n y o b s e r v a t l o n} p o i - n t s a s p o s s l b l e s h o u l d b e i n c l u d e d l n a c l o s e d c l r c u l t o f l e v e 1 s , s o t h a t a n y c l o s l n g error may be distrlbuted a m o n g t h e m " P o l n t s w h l c h c e n n o t b e l n c l u d e d ln such a clrcult a r e c o n s l d . e r e d a s i n t e n n e d i a t e n s l - g h t s $ _{t o w h l c h n o c o r r e c t i o n} c a n b e a p p l i e d , A f o n m s i m l l a r t o t h a t s h o w n 1 n T a b l - e I i s u s e d t o r e c o r d . the survey. ( a) Equlpment 1 w a t e r t u b e L e v e l 1 s m a 1 l b o t t l e o f d . e - a l r e d d l s t l l l e d w a t e r 1 small funnel 3 o r 4 wall plugs 2 p l u g k e y s 2 , t l a s h l l g h t s I f l e 1 d b o o k f s c r a t c h p a d 1 s m a L l s c r e w d r l v e r 1 wlplng cloth 1 e n g l n e e p r s l e v e l a n d t n l p o d 1 l e v e l r o d ( b ) P r o c e d u r e A t e a c h o b s e r v a t l o n p o l n t , _{t h e c o v e r 1 s n e m o v e d f r o m t h e} w a I l s o c k e t b y m e a n s of the key provlded. A f t e r a n y d l r t l s

c a r e f u l l y s c r a p e d f n o m t h e c o n i a l t s u n f a e e s o f t h e w a 1 l s o c k e t a n d p r u g , the latter _{l s s c r e w e d i n t o p l a c e a n d tlghtened} _{w l t h f l n g e r}

p r e s s u r e . _{I f t h e t h r e a d e d h o l e ln the outer end of the plug is used} t o h o l d t h e s o c k e t c o v e r , lt w111 be kept safe and ready- for

neference. _{The water 1evel apparatus ls then hung ln the groove of} t h e w a l I p l u g a n d l e v e l l e d 1 n p o s 1 t L o n , u s l n g t h e - c l a m p a t t h e t o p and screw at the bottom of the instrument"

W h e n a r e a d l n g l s to be taken, the stopcocks are opened and the rubber stoppers removed at both ends of the apparatub. When t h e w a t e r c o l u m n l s q u l t e s t e a d y , each metal sleeve ls- moved up

(25)

c - 2

r e a d t o t h e n e a n e s t 0 . 0 0 5 l n c h , l . e . o n e - h a l - f o f a v e r n l e r dlv1s1on, a t t h e s a m € moment, Good llght l s e s s e n t l a l l n t h i s o p e : : a t l o n , a n 6 f L a g h l L g h t s a r e h e 1 p f u 1 . _{N o t e t h a t t h e n u m b e r s of r,he obsenvatlon} p o l n t s , i n s t r u m e n t , s r _{a n d w a l l p l u g s a n e a L l recor,jed as well as the} l e v e l _{r e a d . i n g s "}

B e f o r e r e m o v L n g the apparatus from any polnt, i t ! s o f c o u r s e n e c e s s a r y t o c l o s e t h e s t o p c o c k a n d r e p l a c e the stopper to avold loslng any ruater..

The survey pnoceeds by reverslng the two end.s of the

l n s t n u n e n t _{o n s u c c e s s l v e p a i r s 6f observailon polnts untll} _{a l I h a v e} b e e n c o v e r e d ' _{f f t h e a v e r a g e d l f f e r e n c e} _{1 n e l 6 v a t l o n} _{o f e a c h p a l n}

of- polnts ls calculated _{at ttte tlme of readlng e.nd entered. in the} t a b I e , m a j o n -e-rrors can almost always be spott6d and correeted before m o v l n g o n . W h e n _ _{t h e s u r v e y l s c o m i l e t e li ls then an easy matten to} c a l c u l a t e t h e r e l a t l v e e l e v a t l o n o f e a c h p o 1 n t .

I f , _{a t t } : e t l m e o f t h e flrst} _{l e v e l} _{s u r v e y o f a s t r n c t u r e ,} a c o n v e i l e n t _{o b s e r v a t l - o n p o l n t i s a s s u m e d t o b e a t - 1 0 . 0 0 o r 2 0 . O O} l n c h e s e l e v a t l o n , _{a l l s u b l e q u e n t 1 e v e l s can be referred} _{t o . t h l s} p o l n t , _{a n d t h l s p o l n t in turn can be referyed to the bench mark} w h l c h l s u s e d . _{f n t h l s w a p all leve1s are convenlently} _{c o r r e l a t e d} l n a s s l n p l e a mannerr as posslble.

( c ) S o u r c e o f E r r o r s

A t t e n t l o n _{t o t h e f o l l o w 1 n g p o l n t s ,} _{g a t h e r e d f r o m e x p e r i e n c e ,} w 1 1 1 g u a n d a g a l n s t _{a v o l d a b l e e r r o r s l}

W h e n e v e r p o s s l b 1 e , s u r v e y s s h o u l d b e c l o s e d s o t h a t maJor e r r o r s _{c a n b e d e t e c t e d and mlnor ones dlstrlbuted.} _{l n s t r u m e n t s} _{r i u s t} b e r e v e r s e d o n e a c h p a l r o f o b s e r v a t L o n p o l n t s .

fn the technlcal operatlon of the lnstnumen'b, sever.s.l p o l n t s _{m u s t b e w a t c h e d "} _{G o o d o b s e r v a t l o n s} _{c a n o n l y b e m a d e w l t h a} _ c l e a n g l a s s t u b e a n d m e t a l s l e e v e , p e r f e c t l y c l e a n - w a t e r , a n d g o o d . l l g h t d u n l n g r e a d l n g s ,

The means of supportlng the lnstrument ls lmportant" For b " : ! r e s u l t s , _{t h e s a m e w a t l p r u g s h o u r d always be used 1n the same} w a 1 l s o c k e t l n s u c c e s s l v e s u r v e y s . _{O t h e r w l s 6 e r r o r s o f a s m u c h a s} 0 . 0 0 3 l n c h e s c a n o c c u . r even wltL new plugs. T h e w a l l p r u g s m u s t b e s c r e w e d flrtnly l n t o t h e w a l l s o c k e t s . - f n p a r t l c u l a n l t m u s t b e e n s u r e d . t h a t the clamp on the lnstnument d.oes not wonk a plug Loose when lt ls tlghtened and the lnstrument is for some reason rn6ved c o u n t e r - c l o c k w l s e _{a b o u t t h e p l u g b e f o r e readlng.} _{T h e s c r e w e l a m p} of the lnstrument itself should-be tlghtened a-standard amount ri.tcft I s a g r e e d u p o n b e t w e e n observers lf a cumulative error ls to be a v o l d e d . _{T h l s e r u o r m a y a m o u n t to as much as o.oo1 lneh} _{p e r} re adlng "