Landslide Investigation by Means of Photogrammetry

7/25/2019 Landslide Investigation by Means of Photogrammetry

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Photogrammetria - Elsevier Publishing Compan y, Amster dam - Printed in The Netherl ands

L A N D S L I D E I N V E S T I G A T I O N B Y M E A N S O F P H O T O G R A M M E T R Y

P. R. SALGUEIRO

International Training Centre for Aerial Survey, Delft The Netherlands)

Received February 2, 1965)

SUMMARY

L a r g e - s c a l e p h o t o g r a m m e t r i c s u r v e y h a s b e e n a p p l i e d t o i n v e s ti g a te a l a n d s li d e

i n a d e n s e l y p o p u l a t e d a r e a o f L a P a z , B o l iv i a . B y t h i s te c h n i q u e , t h e m a s s o f

t h e l a n d sl id e , t h e d i s t r i b u t io n a n d t h e e f f e c ts o f th e m o v e m e n t s o v e r t h e w h o l e

a r e a w e r e s t u d i e d . A s a r e s u l t , m e a n s a n d m e a s u r e s h a v e b e e n p r o p o s e d t o c o n t r o l

t h e l a n d s li d e a n d t o p r e v e n t f u r t h e r d e s t r u c t i v e e ff e c ts .

INTRODUCTION

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

a r e a s w h e r e t h e r e i s a n a s s o c i a t io n w i t h p r o b l e m s o f s o ci a l, e c o n o m i c a n d t e c h n i c a l

n a t u r e , a s in t h e c a s e o f L a P a z c i t y , c a p i t a l o f B o l i v i a , s i t u a t e d i n t h e A n d e s a t

3 , 6 0 0 m a b o v e s e a le v e l i n a n a r r o w v a l le y o f t h e w e s t e r n C o r d i l l e ra a t t h e f o o t o f

t h e A n d e a n g r a n it ic o u t c r o p .

A l a nd s li d e s u ch a s h a s o c c u r r e d a t L a P a z is a c o m m o n p h e n o m e n o n

t h a t c o u l d h a p p e n i n m a n y p l a c es i n t h e w o r l d . T h e p u r p o s e o f t h is p a p e r i s t o

s h o w h o w p h o t o g r a m m e t r i c t e c h n i q u e s m i g h t b e u s e d a s a s t a n d a r d t o o l f o r s ci e n -

t if ic c o n t r o l a n d i n v e s t ig a t i o n in o r d e r t o e s t a b li s h p r e c a u t i o n a r y m e a s u r e s w h i c h

w o u l d m i n i m i z e t h e d e s tr u c t i v e e f fe c t s t h a t t a k e p l a c e i n p o p u l a t e d r e g i o n s o r i n

a r e a s o f i m p o r t a n t m a n - m a d e w o r k s d a m s , b r id g e s , h i g h w a y s , e t c. ).

PHOTOGRAMMETRIC INVESTIGATION

I n M a r c h 1 9 5 8 , o n e o f t h e l a r g e st la n d s li d e s t o o k p l a c e in t h e a r e a s h o w n i n t h e

s t e r e o s c o p ic m o d e l s o f F i g . 1 - 3 . F i g .1 is a p h o t o g r a p h t a k e n 2 y e a r s b e f o r e t h e

e v e n t , s c a le 1 : 1 2 , 0 0 0 1 9 5 6 ) . F i g . 2 w a s ta k e n 1 w e e k a f t e r t h e p h e n o m e n o n ,

s c al e 1 : 6 , 0 0 0 1 9 5 8 ) . F i g . 3 c o r r e s p o n d s t o a e r ia l p h o t o g r a p h y t a k e n 5 1/2 y e a r s

l a te r , s c a le 1 : 1 4 , 0 0 0 1 9 6 3 ) . A s i m p l e s t e r e o s c o p i c c o m p a r i s o n o f t h e m e n t i o n e d

f i g u r e s b r i n g s o u t i n t e r e s t i n g c o n c l u s i o n s t o t h e s u b j e c t u n d e r d i s c u s s i o n .

Photogrammetria, 20 1965) 107-114


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10 8 P R SALGUEIRO

Fig.1. Stereoscopic model, befo re the landslide 1956).

Fig.2. Stereoscopic model, 1 w ee k after the landslide 1958).

T h e n a t u r e o f t h is i n v e s t i g a t io n i m p l i e s a h i g h l y a c c u r a t e t r e a t m e n t s i n c e d a t a

o f h i g h e s t a c c u r a c y w e r e d e s i r e d t o c o m p a r e m o r p h o l o g i c a l c h a n g e s i n p o s i t io n a s

w e l l a s i n h e i g h t . T h i s i n v e s t i g a t i o n w a s c o m p l e m e n t e d b y g e o l o g i c a l a n d f i r s t -

o r d e r l e v e li n g m e a s u r e m e n t s u s in g a W i ld N 3 .

T h e l a r g e - s c a l e a e r i a l p h o t o g r a p h y a n d t y p e o f a e r i a l c a m e r a w e r e a p p r o -

p r i a t e to t h e t y p e o f in v e s t ig a t io n . A W i l d R . C . 5 c a m e r a w i t h A v i o g o n l en s , t h e

Z e i s s c a m e r a w i t h P l e o g o n le n s a n d t h e F a i r c h i l d T . 1 2 c a m e r a w i th P l a n i g o n l e n s,

r e s p e c ti v e ly , w e r e e m p l o y e d . G l a s s p l a te s o f 6 m m t h i ck n e s s w h e r e u s e d o n t h e

u n i v e r s al p h o t o g r a m m e t r i c i n s t ru m e n t , a u t o g r a p h W i l d A 7 , a f t e r c a r e f u l a d j u s t m e n t .

Photograrnmetr a, 20 196 5) 107-114


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LANDSLIDE INVESTIGA TIONBY MEA NS OF PHOTOGRAMMETRY 109

C o n t r o l p o i n t s o f a f i r s t - o r d e r t r ia n g u l a t i o n n e t o f L a P a z c i t y w e r e u s e d a s

g r o u n d c o n t ro l . F i v e w e l l- d e f in e d c o n t r o l p o i n t s h a v e g i v e n a g o o d a c c u r a c y f o r

t h e p l o t ti n g a n d c o n t r o l f o r e a c h p a i r o f p h o t o g r a p h s , o b t a i n in g a m e a n s q u a r e

e r r o r i n p o s i t i o n o f c a . 0 .5 m a n d i n h e i g h t o f c a . 0 . 3 5 m i n th e m o d e l s . T h e c o n t r o l

w a s v e r y a c c u r a t e a n d t h e l a r g e s t d i s c r e p a n c y f o u n d w a s o f th e o r d e r o f 1 .0 m i n X

a n d Y . T h e g i v e n r e s u l ts i n d i c a te t h a t t h e w o r k c a r r i e d o u t o n t h e W i l d A 7 w a s o f

f i rs t q u a l i ty . T h e i n d i c a t e d m e a n s q u a r e e r r o r s i n p o s i t io n o f 0 . 5 m a n d i n h e i g h t

o f 0 . 3 5 m a r e fu l l y i n a c c o r d a n c e w i t h t h a t c a n b e e x p e c t e d f r o m t h e s e s m a l l - s c a l e

p h o t o g r a p h s . F r o m t he p h o t o g r a p h s 1 : 6 , 0 0 0 a b o u t h a lf t h es e va l ue s c o u l d be

e x p e c t e d .

U n d e r t h e c o n d i t i o n s o u t l i n e d a b o v e f o r p r e c i s i o n , th e t h r e e m o d e l s w e r e

p l o t t e d o n t h e W i l d A 7 a t t h e s c a l e 1 : 1 , 0 0 0 , s t a r t i n g w i t h t h e 1 9 5 8 m o d e l w h i c h

s e r v e d a s a b a s e t o d e l i n e a t e t h e e f f e c t s a n d s h a p e o f t h e l a n d s l i d e . I t w a s u s e d

a f t e r w a r d s a s a r e f e r e n c e f o r t h e 1 9 5 6 a n d t h e 1 9 6 3 p l o t t in g m o d e l s . A l t h o u g h t h e

s c a le s o f t h e a i r p h o t o g r a p h s a r e d i f f e r e n t a n d i n p a r t i c u l a r t h e s c a le s o f 1 9 5 6 a n d

1 9 6 3 a r e n o r m a l l y t o o s m a l l f o r r e s ti t u t io n i n a sc a l e 1 : 1 , 0 0 0 , t h i s m a p p i n g s c a l e

h a s b e e n a c c e p t e d i n o r d e r t o f a c i li ta t e t h e c o m p a r i s o n o f t h e t h r e e m a p s . T h e

b a s i c c h a n g e s o f m o r p h o l o g y d u e t o th e l a n d sl id e a n d i ts c o m p a r i s o n a r e s h o w n

o n t h e t h r e e p h o t o g r a m m e t r i c c o n t r o l m a p s , F i g . 4 - 6 .

A s s o o n a s t h e p l o t t in g o f t h e f ir s t m o d e l w a s f in i s h e d , a t r a n s p a r e n t r e t i c u le

o f g r i d li n e s w a s c o n s t r u c t e d o n t h e p l o t t i n g t a b l e w i t h i ts l i n e s p a r a l l e l t o t h e

X - a n d Y - a x e s o f t h e m a c h i n e . T h e s h a p e o f th e g r id w a s d e l i n e a te d b y t h e

Fig.3. Stereoscopic m ode l, 5x/J yea rs later 1963).

Photogrammetria 20 1965 ) 107-114


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l l 0 P. R, SALGUEIRO

l O m

L j

Fig.4. Lar ge-scale map of the 1956 model.

landslide Fig.5), 1958 photographs, and it was decided to use grid lines with 10 m

intervals. With this grid the locations of 680 points were obtained, for which the

coordinates X, Y and Z were read and registered simultaneously by means of the

EK3 print and the I.B.M. punch-card. The punch-card data were taken to the

electrical I.B.M.602 computing machine. The practical method of running readings

on the Wild A7 autographs to intervals of 10 m in the three models was very

simple, since a draftsman helped to carry the spot points by means of the X- and

Y-wheels of the plotting table. The operator merely moved the Wild A7 height disc

twice, to put the floatingmarkonthegroundinordertoobtainheightdoublereadings.

Photogrammetria

20 1965) 107-114


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LANDSLIDE INVESTIGA TIONBY MEA NS OF PHOTOGRAMMETRY 111

Fig.5. M ap of the 1958 model .

W i t h t h e p u n c h - c a r d s i t w a s p o s s i b le t o c a r r y o u t c o m p u t a t i o n s o f t h e a r e a

a n d t h e v o l u m e s o f t h e a f f e c te d re g i o n. T h e v o l u m e V , w a s c o m p u t e d a n d r e f e r re d

t o X , Y a n d Z a r b i t r a r y p l a n e s u s in g th e d a t a o f t h e p h o t o m o d e l o f 1 9 5 6 . V o l u m e s

V ~ a n d V 3 w e r e c o m p u t e d w i th t h e p h o t o m o d e l s ta k e n i n 1 9 5 8 a n d 1 9 6 3 . T h e

d i f f e r e n c e V 1 - V 2 = x V 1, g a v e u s a v o l u m e f o r t h e e n t i r e s o il m o v e m e n t d u e

t o t h e l a n d s l id e o v e r a n o l d t e r r a c e . 1 / 2 - V 3 = ~x V 2 , y i e l d s t h e e f f e c t w h i c h h a s

p r o d u c e d a d if f e r e n t i a l v o l u m e , d u e t o th e s e d i m e n t a t i o n , s i n k i n g o f s oi l, e r o s i o n

a n d w e a t h e r i n g e f fe c t s w h i c h h a v e t a k e n p l a c e i n t h e a r e a w i t h in a n i n t e rv a l o f

51 /2 yea r s .

Photogrammetria

20 196 5) 107-114


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11 2 P.R . SALGUEIRO

Fig.6. M ap of the 1963 model.

T h e m e t h o d u s e d f o r t h e c o m p u t a t i o n o f t h e v o l u m e w a s b a s e d o n t h e

S i m p s o n s f o r m u l a s :

A

V = ~ ~Vhl + 2 ~ h 2 + 3~Vh.~ + 4~Yh4)

A

V = ~ h l + h 2 + h a )

Photogrammetria

20 196 5) 107-114


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L A N D S L ID E I N V E ST I G A T IO N B Y M E A N S O F P H O T O G R A M M E T R Y 1 1 3

The area was computed using the simple orthogonal coordinates of the

points on the periphery:

2 A = ~ xi (Yi-a -Y~+1)

giving an area of 54,316 mL

The computed results gave the following figures concerning the mass of

soil moved over an older terrace. Seven days after the landslide took place the

movement was 48,895.5 mZ; 51/2 years after the second measurement, made in

1958, the sedimentation, erosion and sinking was 73,904.1 m L The total move-

F i g .7 . F r a c t u r e s o n w a l l s d e l in e a t e c o n c e n t r i c a r e a s a l o n g t h e l a n d s l id e a x e s .

Photogrammetria

2 0 1 9 6 5) 1 0 7 - 1 1 4


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11 4 P. R. SALGUEIRO

m ent s ince i ts o r ig ina l s t a t e , befo re t he l ands l ide t o ok p l ace , i s 122 ,7 99 .6 m 3. I t

h a s b e en p l an n e d t o co n t r o l t h is e f f ec t w i t h in an o t h e r 5 - y ea r p e r i o d .

A carefu l i nves t iga t ion o f f r ac tu res i n t he bu i ld ings shown on the aer i a l

pho tos wi th in the ne ighbor ing a rea c lose t o t he lands l ide , pa r t l y by g round inspec-

t i on and par t l y on the pho to grap h F ig .7 ) , shows c l ear ly t he p r inc ipa l ax i s o f t he

phenomenon ind ica t ing tha t a fu tu re l ands l ide wi l l o r ig ina t e a long tha t ax i s , and

the so i l ma ss which i s go ing to mov e will fo rm ano th er t e r race as i n t he case o f

areas o f s imi la r m orp ho lo gy nar row va l l eys ) . Th e conc en t r i c a rcs on the aer ia l

pho tos show the fu tu re m oving area t ha t wi ll cause des t ruc t ive e f fec t s. I t shou ld

b e co n c l u d ed t h a t ad eq u a t e s ecu r i t y me as u r e s m u s t b e co n s i d e r ed b e f o r e t h e o c -

cu r rence o f ano ther l ands l ide .

CONCLUSIONS

1 ) P h o t o g r am m et r y i s t h e ad eq u a t e , p r ec i s e an d ti me- m o n ey s av in g s o lu t io n

f o r co n t ro l o f l an d s li d e p h en o m en o n , p r o v i d ed t h a t ad eq u a t e a ir p h o t o g r ap h y i s

avai lable.

2 ) The a i r pho tograph ic i n t e rp re t a t i on , i n connec t ion wi th t he f ac t s found

ou t in the m orpho log ica l change s o f t he a rea s tud ied , g ives a c lear p i c tu re o f

occu r rence o f fu tu re even t s wh ich w ill t ake p l ace caus ing the des t ruc t ion o f a

l a rge nu m ber o f houses a s it i s show n in F ig .7 . A s a r esu l t o f t h is i n ference , t he

m os t appro pr i a t e ru l es m igh t be d raf t ed by the loca l techn ica l au thor i t i es i n o rder

to p reven t fu tu re l ands l ides .

3 ) Th e o r ig in o f t he l ands l ide can b e exp la ined , base d on the f ind ings by

mea n s o f p h o t o g r am m et r y an d g eo l o g i ca l o b s e r v a t io n s .

4 ) A carefu l phys i ca l ana lys i s based on the e f fec t s o f defo rmat ion , f r ac-

tu res , s i nk ing and d i sp l acement , wi l l permi t es t ab l i shmen t o f t he fo rce-vec to r d i s -

t r i bu t ion and i ts e f fec t s wi th in t he a rea .

Photogrammetria 20 1965) 107-114

Landslide Investigation by Means of Photogrammetry

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