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Miyakawa, I.; National Research Council of Canada. Division of Building Research

PREFACE

The D i v i s l o n o f B u i l d i n g R e s e a r c h i s k e e n l y i n t e r e s t e d i n t h e e n g i n e e r i n g problems p r e s e n t e d by muskeg and i s c u r r e n t l y engaged i n a s t u d y of t h e

e n g i n e e r i n g c h a r a c t e r i s t i c s o f t h e c o n s t i t u e n t m a t e r i a l , p e a t . C o n t i n u i n g l i a i s o n i s m a i n t a i n e d w i t h o r g a n i z a -

t i o n s i n o t h e r c o u n t r i e s w i t h a similar i n t e r e s t i n o r g a n i c t e r r a i n problems.' The D i v i s i o n i s p a r t i c u l a r l y p l e a s e d t o have c l o s e l i n k s w i t h t h e Hokkaido Development Bureau, i n J a p a n s n o r t h e r n m o s t i s la n d , t h r o u g h D r . Isamu Miyakawa, C h i e f o f t h e S o i l Mechanics Branch o f t h e

B u r e a u ' s C i v i l E n g i n e e r i n g R e s e a r c h I n s t i t u t e .

F o r s e v e r a l y e a r s , D r . Miyakawa and h i s c o l l e a g u e s have been engaged i n r e s e a r c h i n t o t h e e n g i n e e r i n g

. p r o p e r t i e s of p e a t , a s u b j e c t which i s s t i l l l i t t l e u n d e r s t o o d . These r e p o r t s , which a r e c o n c e r n e d c h i e f l y w i t h t h e f u n d a m e n t a l and e n g i n e e r i n g p r o p e r t i e s o f p e a t as a s o i l s h o u l d , t h e r e f o r e , b e o f p a r t i c u l a r i n t e r e s t . O t t a w a R.F. Legget J a n u a r y , 1962 D i r e c t o r

T i t l e :

NATIONAL RESEARCH COUNCIL OF CANADA

T c c h n i c a l T r a n s l a t i o n 1001 S o i l e n g i n e e r i n g r e s e a r c h on p e a t y a l l u v i a R e p o r t No. 1, G e o t e c h n i c a l p r o p e r t i e s of e x i s t i n g g r a v e l r o a d s o v e r p e a t a r e a s

...

i n t h e 1shlkar.l. d i s t r i c t Page 3 Report No. 2, C o n t r i b u t i o n s t o some geo-

technical e x p l o r a t i o n methods f o r p e a t

...

b o p Page

77

R e p o r t No.

3 ,

General p h y s i c a l p r o p e r t i e s of p e a t i n t h e I s h i k a r i d i s t r i c t w i t h s p e c i a l r e f e r e n c e t o t h e m o i s t u r e

-

...

i g n i t i o n l o s s r a t i o Page 103

Author: Isamu Miyakawa

R e f e r e n c e : B u l l e t i n No. 20, C i v i l E n g i n e e r i n g Research I n s t i t u t e , Hokkaido Development Bureau, J a p a n . J a n u a r y ,

1959. 88

p .

SOIL ENGINEERING RES1:ARCH O N PEATY ALLIJVIA

REPORT NO. 1

GEOTECFINICAL PROPZRTIES OF EXISTING GRAVEL ROADS

OVZR PEAT AREAS I N TIJE I S H I K A R I DISTRICT

Summary - The p r e s e n t i n v e s t i g a t i o n s were c a r r i e d o u t t o a s c e r t a i n t h e g e o t e c h n i c a l p r o p e r t i e s o f g r a v e l r o a d s over p e a t a r e a s i n t h e lower I s h i k a r i d i s t r i c t w i t h a view t o p r o v i d i n g t h e b a s i c d a t a n e c e s s a r y t o establish a r a t i o n a l p o l i c y f o r t h e c o n s t r u c t i o n o f f u t u r e r o a d s i n p e a t a r e a s . The p r e s e n t r e p o r t d e a l s w i t h t h e r e s u l t s of i n v e s t i g a t i o n s of b e a r i n g c a p a c i t y s e t t l e m e n t and a s s o c i a t e d f a c t o r s on e x i s t i n g r o a d s i n and around t h e S h i n o t s u d i s t r i c t . Contents Foreword... 4 1. Items I n v e s t i g a t e d . .

...

4

(1) Routes and s i t e s of investigation...

4

(2) Items i n v e s t i g a t e d and methods...,.

5

2. R e s u l t s of Investigations... 9 (1) I n i t i a l conditions...

9

( 2 ) S t r u c t u r e and m a t e r i a l o f roads...

9

( 3 ) S o i l distribution...,... 11 ( 4 ) D i s t r i b u t i o n of g e o t e c h n i c a l p r o p e r t i e s a g a i n s t depth. 1 2 ( 5 ) C o e f f i c i e n t of b e a r i n g capacity...,... 1 4

Conclusions...

18

Foreword

~-

One of t h e b a s i c problems i n developing a p e a t a r e a i s t h e

c o n s t r u c t i o n and maintenance of roads. E x i s t i n g r o a d s i n p e a t a r e a s i n Hokkaido have had a h i s t o r y of s e v e r a l decades s i n c e t h e i n i t i a l r e c l a m a t i o n p e r i o d ; however, t h e heavy t r a f f i c c o n d i t i o n s of today a r e a r e c e n t development. They have been transformed from wet

f i e l d s f i r s t t o simple a g r i c u l t u r a l r o a d s , and t h e n t o t h e p r e s e n t r o a d s which have evolved t o meet t h e changes i n t r a f f i c c o n d i t i o n s o The b e t t e r f u n c t i o n i n g o f r o a d s h a s come about n o t o n l y through d i r e c t improvement and r e p a i r s , b u t a l s o , f o r example, through changes i n environment due t o t h e c o n s t r u c t i o n of d r a i n a g e systems o f every s c a l e and t o r i p a r i a n xorks.

I n o r d e r t o b u i l d r o a d s i n p e a t a r e a s o r t o make n e c e s s a r y improvements on them, i t i s e s s e n t i a l t o know t h e b e a r i n g c a p a c i t y

required t o c a r r y t h e t r a f f i c l o a d a d e q u a t e l y , and t h e c o n d i t i o n s f o r t r e a t i n g t h e p e a t a r e a i n o r d e r t o achieve t h i s b e a r i n g c a p a c i t y .

I n t h e b e l i e f t h a t i t would be a n e f f e c t i v e method of determin- i n g t h i s i n f o r m a t i o n , i n 1955 t h e a u t h o r d e c i d e d , a s an i n i t i a l s t e p , t o a t t e m p t a s o i l s and engineering a n a l y s i s of some of t h e r o a d s i n t h e v i c l n i t y of t h e I s h i k a r i River system around t h e

Shtnotsu d i s t r i c t , I t was decided t o i n v e s t i g a t e t h e g e o t e c h n i c a l c o n d i t i o n of e x i s t i n g , m u e l r o a d s and t o compare t h e i r behaviour under normal t r a f f i c and weather c o n d i t i o n s i n o r d e r t o a r r i v e a t a s t a n d a r d f o r f u t u r e p l a n n i n g ancl d e s i g n i n g and t o f u r n i s h a b a s i s of procedure i n t h e l i g h t of t h e r e s u l t s , T h i s i n v e s t i g a t i o n

c o n s t i t u t e s a f i r s t s t e p i n a g e n e r a l study o f r o a d s i n p e a t a r e a s .

1. Items I n v e s t i g a t e d (1) Routes anti s s e s o f i n v e s t i g a t i o n

Representative s i t e s which are shown i n Tab12 1.1 and F i g . 1.1,

were s e l e c t e d from a p a r t of t h e road system on t h e l e f t bank of t h e I s h i k a r i River around t h e Shinotsu d i s t r i c t (which i s l o c a t e d down- stream on t h e r i g h t bank of t h e I s h i k a r i ) , t h e c h o i c e b e i n g based on

such f a c t o r s a s t h e c l a s s of road and t h e amount of t r a f f i c . Photograph 1.1 shows such a s i t e and i t s environment.

( 2 ) Items i n v e s t i g a t e d and methods

The i n v e s t i g a t i o n was t o i n c l u d e e x c a v a t i o n , b o r i n g , and

u n d i s t u r b e d sampling, and w a s t o be c a r r i e d o u t a c c o r d i n g t o c l a s s - e s of r o a d s , t h e time e l a p s e d s i n c e c o n s t r u c t i o n , and t y p e s of bases. The a i m of t h e i n v e s t i g a t i o n was t o c o l l e c t d a t a which would permit a s t u d y of t h e r e l a t i o n s h i p between t h e type and volurne o f t r a f f i c on t h e one hand and t i m e , on t h e o t h e r , by examining t h e s t r u c t u r e of t h e r o a d , t h e m a t e r i a l used, degree of compression of t h e roadbed and base and t h e t o t a l s e t t l e m e n t , o r by d e t e r m i n i n g t h e changes compared w i t h t h e a 2 j a c e n t undeveloped a r e a , It was planned t o i n v e s t i g a t e t h e f o l l o w i n g m a t t e r s :

( i ) I n v e s t i ~ a t i o n o f i n t i a l c o n d i t i o n s , This i n v e s t i g a t i o n was t o i n c l u d e such items a s t h e c l a s s e s of r o a d s , t h e source m a t e r i a l on t h e i n i t i a l p l a n and d e s i g n , t h e time e l a p s e d a f t e r completion, c o n d i t i o n of t r a f f i c ( t y p e s , l o a d s , volumes), c o n d i t i o n of r e p a i r , and t h e m e t e o r o l o g i c a l c o n d i t i o n s . I t was decided

t o

c o n f i n e t h e e f f o r t of o b t a i n i n g lnformntion on t h e s e b a s i c d a t a and environmental c o n d i t i o n s t o e x i s t i n g r e c o r d s i n t h e higjlways admin- i s t r a t i v e o f f i c e s ( f o r r o a d s i n q u e s t i o n ) , No s p e c i a l i n v e s t i g a t i o n was made f o r t h i s purpose.

( i i ) I n v e s t i g a t i o n of ~ e o t e c h n i c a l properties. The i n v e s t i g a t i o n

of g e o t e c h n i c a l p r o p e r t i e s w a s concerned n o t o n l y w i t h t h e r o a d s b u t a l s o w i t h t h e a d j a c e n t a r e a s ,

A , U e s of t h e m n e r a l i n v e s t i ~ a t i o n g ( a ) Roads

The i n v e s t i g a t i o n s were conducted by t e s t p i t e x c a v a t i o n s t o ground water l e v e l and by b o r i n s and soundin2 below t h e cqround w a t e r l e v e l , over a l l o r h a l f the road c r o s s - s e c t i o n , depending on whether o r n o t t h e whole c r o s s - s e c t i o n could be i n v e s t i g a t e d w i t h o u t

i n t e r r u a t i n g t r a f f i c . T h i s i s p a r t i c u l a r l y d e s i r a b l e i n p l a c e s where t h e r e a r e marked d i f f e r e n c e s I n t h e d r a i n a r e d i t c h e s and t h e

( I ) I n v e s t l , ~ a t i o n of t h e c o u ~ ~ ~ o s i t l o n of r o a d s .

--

The p r e s e n t c o n d i t i o n of t h e s u r f a c e , t h e i n t e r n a l s t r u c t u r e and, i n t h e c a s e of g r a v e l r o a d s , t h e c o n s t i t u e n t m a t e r i a l under t h e s u r f a c e l a y e r were i n v e s t i g a t e d .

( i i ) I n v e s t i ~ a t i o n of t h e s o i l p r o f i l e . The s o i l p r o f i l e down t o t h e substratum of c l a y or sand below t h e p e a t l a y e r was i n v e s t l - g a t e d by p i t e x c a v a t i o n and by p e a t sampler ( ~ i g . 1.2 and P h o t o ~ ~ a p h

1 . 2 and 1.3).

( i i i ) I n v e s t i g a t i o i i of g e ~ e r a l g h v s i c a l p r o p e r t i e s . ' D e n s i t y , m o i s t u r e c o n t e n t , and i g n i t i o n l o s s were determined from u n d i s t u r b e d

samples which were o b t a i n e d by c u t t i n g down t o t h e ground w a t e r l e v e l and by means of z 3" d i a m e t e r t h i n - w a l l p i s t o n sampler below t h a t l e v e l (Photo,g-a;;h 1.4). The i n v e s t i g a t i o n s were c a r r i e d o u t a t t h e road c e n t r e , t h e s h o u l d e r of t h e road and t h a t of t h e drainage d i t c h .

( i v ) Vane

t e s t .

A t t h e same l o c a t i o n s a s ( i l l ) , i n a range o f l e s s t h a n 50 crn, i n v e s t i g a t i o n s were made of t h e s t r u c t u r e of t h e road b a s e w i t h a vane t e s t e r ( d i a m e t e r 5.5 cm, and h e l g l l t 11 cm). T e s t i n g extended t o a d e 2 t h of 1

-

2 m i n t h e c l a y l a y e r below t h e p e a t l a y e r (Photograph 1 . 5 ) .

( v ) P e n e t r a t i o n t e s t . A t t h e same l o c a t i o n s , u s i n g s t a t i c cone penetrometers of v a r i o u s t y p e s ( s i n g l e rod SP-10 t y p e : a r e a 1 0 cm2, nose a n g l e 30°; double t u b e ';JP-20 t y p e : a r e a 20 cm2, nose a n g l e 30° and f r i c t i o n s p r i n g FP t y p e )

-

measurements were made of pene- t r a t i o n r e s i s t a n c e ( P i g . 1.2, Photograph 1 . 6 ) . These were combined w i t h t h e r e s u l t s of t h e i n v e s t i g a t i o n of t h e s o i l p r o f i l e a s

d e s c r i b e d above, 2nd were taken a s soundings. S t u d i e s were a l s o conducted t o examine t h e s u i t a b i l i t y of a p p l y i n g t h e s e methods t o p e a t a r e a s . I n a d d i t i o n , t h e a u t h o r i n t e n d s t o compare them with t h e r e s u l t s of t h e vzne t e s t ; t o i n v e s t i g a t e t h e c o r r e l z t i o n between vane s h e a r and p e n e t r e t i o n index ( p e r ~ e t r a t i o n r e s i s t a n c e p e r u n i t a r e a of t h e h o r i z o n t a l cone cross-cect,ion, and t o extend t h e use of t h e cone p e n e t r c n ~ e t e r i n t h e p e a t l a y e r . Some doubt e x i s t s regard- i n g t h e a p p l i c a t i o n of t h e so-cal.led standard. p e n e t r a t i o n t e s t t o

p e z t l a y e r s and t h e s o f t c l a y l a y e r which i s fcund d i r e c t l y below t h e p e a t . The author a l s o i n v e s t i g a t e d t h i s a s p e c t .

( v i ) Measurement of t h e ,mound vrater ,1_eygl. I t must be assumed

t h a t t h e r e a r e s e a s o n a l v a r i a t i o n s . However, measurements were made of t h e ground w a t e r l e v e l a t t h e time of t h e i n v e s t i g a t i o n by e x c a v a t i o n and by auger boring. T h i s was done a t f i v e d i f f e r e n t l o c a t i o n s

-

i n t h e c e n t r e of t h e r o a d , on t h e s h o u l d e r of each s i d e d i t c h , and midway between t h e s e two p o i n t s wherever t h e r e was a

wide c r o s s - s e c t i o n a l a r e a .

( v i i ) Other t-ests. It i s d o u b t f u l i f s i g n i f i c a n t r e s u l t s can be o b t a i n e d with a one dimensional c o n s o l i d a t i o n t e s t when a p p l i e d t o such a m a t e r i a l a s p e a t which i s f i b r o u s and s o f t , with marked a n i s t r o p y . However, i t was decided t o conduct some s t u d i e s on samples o b t a i n e d i n t h e s t a n d a r d p e n e t r a t i o n t e s t s o r by t h e t h i n - w a l l sampler.

( v i i i ) P l a t e b e a r i n g t e s t . Since a l l roads i n v e s t i g a t e d a r e

g r a v e l r o a d s w i t h a deep p e a t l a y e r a s a b a s e , t h e a p p l i c a b i l i t y of t h e t e s t must be examined. During t h e i n v e s t i g a t i o n I t was decided t o t r y t h e p l a t e b e a r i n g t e s t t o a s c e r t a i n t h e a b i l i t y o f g r z v e l r o a d s i n p e a t a r e a s t o s u p p o r t t h e t r a f f i c load.

The c e n t r e of t h e road was chosen a s t h e p o i n t of i n v e s t i g a t i o n . T e s t s were a l s o made on t h e s h o u l d e r of t h e road when i t w a s f e l t

t h a t t h e r e might be a marked d i f f e r e n c e .

The t e s t s were c a r r i e d o u t a t t h e same d e p t h a t each s i t e . To sum up:

(1) For t h e g r a v e l l e d s u r f a c e of t h e road and t h e m i n e r a l s o i l substratum t h e d e t e r m i n a t i o n s were r a d e by t h e p l a t e b e a r i n g metk~od w i t h r e s p e c t t o each l a y e r ;

( 2 ) For t h e s u r f a c e of t h e p e a t l a y e r u n d e r l y i n g t h e m i n e r a l s o i l f i l l , and f o r a lower l a y e r i n t h e p e a t (30

-

50 cm below t h e p e a t s u r f a c e ) , t h e deterrnirlations were made a s f o l l o w s :

V i t h a n i n i t i a l load of 0.1 kg/crn 2, l o a d ir~crernents o f

each i n c r e m e n t , i f t h e s e t t l e m e n t f i v e n ~ l n u t e s a f t e r a s : ~ e c l f i e d tinle w a s l e s s t h a n 5% of t h e t o t z l s e t t l e m e n t ; up t o t h a t p o i n t , i t was c o n s i d e r e d complete and t h e n e x t l o a d w a s a p p l i e d . For tkiese t e s t , g r a v e l ' was 1.oad.ed o n a truclc and. t h e l o a d w a s a p p l i e d w i t h a h y d r a u l i c jack p l a c e d b e n e a t h t h e t r u c k . The l o a d w a s measured w i t h a p r o v i n g r i n g . The l o a d was i n c r e a s e d u n t i l t h e t r u c k l i f t e d o r u n t i l i t was c l e a r t h a t breakage and s e t t l e m e n t were t a k i n g p l a c e . S e t t l e m e n t was measured by a d i a l i n d i c a t o r o r , when t h e s e t t l e m e n t was markedly l a r g e , by a f o l d i n g s c a l e w i t h a s t a n d . P!easurements were t a k e n e v e r y minute.

The p l a t e 11cr;d w a s c i r c u l a r i n shape w i t h a d i a m e t e r o f 30

o r 50

crn

d e p e n d i n g on t h e b e a r i n g c a p a c i t y o f t h e p o i n t u n d e r i n v e s t i g a t i o n ; i n some c a s e s b o t h p l a t e s were used. ( b ) Pea.t m o u n s

S i m i l a r d a t a were o b t a i n e d on ground a d j a c e n t t o t h e r o a d , 1 . e . :

( i ) i n v e s t i g a t i o n o f s o i l . p r o f i l e ( a s d e s c r i b e d a b o v e ) ;

(11) i n v e s t i g a t i o n o f g e n e r a l p h y s i c a l p r o p e r t i e s c a r r i e d o u t as d e s c r i b e d above a t p o i n t s 2 , 5 , and 20 m from t h e s h o u l d e r o f

d r a i n a g e d i t c h ;

(111) vane s h e a r t e s t ( a s a b o v e ) ; ( i v ) p e n e t r a t i o n t e s t (as a b o v e ) ;

( v )

measurements of p o u n d w a t e r l e v e l were made a t p o i n t s

0 . 3 , 2 , 5 , and 20 m from t h e o u t e r s h o u l d e r o f d r a i n a g e d i t c h , t a k i n g a d v a n t a g e of a u g e r h o l e s , B.

Kate-bear in^

t e s t s i t e s A t s i t e s where p r i n ~ a r l l y p l a t e b e a r i n g t e s t s were t o be c z r r i e d o u t t h e i n v e s t i g a t i o n s were c o n d u c t e d i n a sin11la.r f a s h i o n as a t s i t e s where t h e g e n e r a l i n v e s t i g a t i o n s were c a r r i e d o u t . I n t h e s e l o c a t i o n s t h e i n v e s t i g a t i o n s c o n s i s t e d o f : (1) c r o s s - s e c t i o n a l ~ ~ o f i l e o f t h e r o a d and t h e s o i l p r o f i l e a t t h e s i t e o f i n v e s t i g a t i o n ; ( 1 1 ) p l a t e b e a r i n g t e s t ; ( i l l ) p e n e t r a . t i o n t e s t ; ( i v ) c o u n d - w a t e r l e v e l . measurements,

I n v e s t i g a t i o n s of items ( i i i ) and ( i v ) should be conducted i n a d j a c e n t a r e a s and a t a s many l o c a t i o n s as p o s s i b l e .

2. R e s u l t s of I n v e s t i c r a t i o ~

(1) I n i t i a l c o n d i t i o n s

With r e s p e c t t o t h e i n i t i a l c o n d i t i o n s very f e o r e c o r d s of t h e t y p e o r i g i n a l l y a n t i c i p a t e d were a v a i l a b l e . I t can be deduced from t h e h i s t o r y of t h e r o a d s i n v e s t i g a t e d t h a t a simple a g r i c u l . t u r a 1 road was f i r s t c o n s t r u c t e d over t h e o r i g i n a l swamp land a t t h e s t a r t of development i n t h e M e i j i p e r i o d (approximately 1860

-

1 9 1 2 ) ,

and t h a t it h a s s i n c e been improved from time t o time i n accorhdance with t h e changes i n the t y p e s and volurr~e of t r a f f i c . Since t h e s e roads were not b u i l t i n accordance with any preconceived p l a n ,

n o t h i n g was known of t h e i n i t i a l c o n d i t i o n s , nor w a s t h e r e any d a t a on t h e i r h i s t o r y .

It has n o t been p o s s i b l e t o o b t a i n s u f f i c i e n t d a t a on " t r a f f i c i n v e s t i g a t i o n u o r maintenance, which were f e l t t o be e s s e n t i a l . The o n l y r e c e n t i n f o r m a t i o n a v a i l a b l e was t h a t s u p p l l e d by t h e Sapporo Development and C o n s t r u c t i o n Brunch of t h e Development Bureau on t h e r e s u l t s of a t r a f f i c survey made on Eept. 27 and 28, 1955, on t h e Sapporo-Mumata r o u t e . The d a t a have been t a b u l a t e d s o a s t o g i v e an i n d i c a t i o n of t h e t r a f f i c c o n d i t i o n s on t h i s road. The amount of t r a f f i c , averaged over two days d u r i n g a twelve-hour p e r i o d between 7 a . m . t o 7 p.m., i s shown i n Table 1 . 2 .

I t was t h e r e f o r e decided t o i n v e s t i g a t e t h e g e o t e c h n i c a l condi- t i o n s of e x i s t i n g r o a d s , t o compare t h e s e w i t h t h e p r o p e r t i e s of a d j a c e n t n a t u r a l s o i l , and t o use them a s c l u e s on which t o base f u t u r e p l a n n i n g and d e s i g n , and f o r an o b j e c t i v e s t a n d a r d of opera- t i o n . Fig. 1.3 shows t h e c r o s s - s e c t i o n s and i t e m s c o n s i d e r e d a t t h e s i t e s of g e n e r a l i n v e s t i g a t i o n s .

S t r u c t u r e and m a t e r i a l of roads

Fig. 1.4 shows r e s u l t s , o f t h e i n v e s t i g a t i o n s i n t o road composi- t i o n a t s i t e s where g e n e r a l i n v e s t i g a t i o n s had been conducted. A

g e n e r a l summary i s g i v e n i n Table 1.3.

A s h a s been mentioned p r e v i o u s l y , t h e r o a d s had n o t been b u i l t under any p l a n ; t h u s , t h e t r a c e s of r e p a i r s and improvements were c l e a r l y v i s i b l e . The g e n e r a l composition of t h e r o a d , f o r example,

a t Chuokakusan, r e v e a l s l a y e r s of

eat

on a p e a t f o u n d a t i o n , with a l t e r n a t e l a y e r s of s o i l and sand ( i n many i n s t a n c e s c l a y ) and b a l l a s t . The t h i c k n e s s d i f f e r e d i n accordance w i t h t h e c l a s s of road and t h e c o n d i t i o n of t r a f f i c . A s shown i n t h e i l l u s t r a t i o n s and t a b l e s , t h e t h i c k n e s s i n c r e a s e s w i t h an a s c e n d i n g s c a l e of c l a s s e s more o r l e s s i n t h e o r d e r o f No. 5 t o No. 1.

Examining a road embankment p r o f i l e a t i t s c e n t r e t a k e , f o r example, t h e v o l c a n i c 3sh l a y e r ( a t h i n l a y e r l o c a t e d 10

-

15 cm below t h e s u r f a c e ) colnrnonly observed i n t h e s u r f a c e l a y e r of p e a t a r e a s i n t h e I s h i k a r i d i s t r i c t and c o n s i d e r t h e t h i c k n e s s of t h e road embankment which h a s been c o n s t r u c t e d on I t . The measurements, as shown i n t h e i l l u s t r a t i o n s and t h e t a b l e , were: 2 1 cm f o r No. 5

(town and v i l l a g e r o a d ) ; 57 and 80 cm f o r No. 3 and 4 ( p r e f e c t u r a l r o a d s ) ; 62 and 180 cm f o r No. 1 and 2 (primary l o c a l r o a d s ) .

F u r t h e r , t h e o v e r a l l t h i c k n e s s o f t h e m i n e r a l s o i l l a y e r , i n c l u d i n g t h e g r a v e l l a y e r and e x c l u d i n g t h e p e a t y m a t e r i a l a t t h e c e n t r e o f t h e road were, from No. 5 t o No. 1, 2 3 , 38, 40, 48 and 113 cm,

r e s p e c t i v e l y . The t o t a l t h i c k n e s s e s of t h e g r a v e l a t t h e c e n t r e of t h e r o a d , from No. 5 t o No. 1 were, r e s p e c t i v e l y , 9 , 11, 25, 30, and 39 cm. These f i g u r e s g i v e an i n d i c a t i o n of t h e composition of t h e road s t r u c t u r e f o r varvious c l a s s e s .

A comparison of t h e t h i c k n e s s v a l u e s of t h e s h o u l d e r s and t h e c e n t r e s i n t h e columris d e s i g n a t e d

"

t h i c k n e s s of gra.vell' and t h i c k - n e s s of t h e s o i l l a y e r " , i n many c a s e s show t h e o v e r a l l t h i c k n e s s t o be g r e a t e r a t t h e s h o u l d e r . T h i s probably i n d i c a t e s t h a t a t t h e b e g i n n i n g of c o n s t r u c t i o n t h e road f i l l c o n s i s t e d of p e a t ( d u g from s i d e d i t c h e s , e t c . ) , a l s o , t h a t owing t o t h e weakness o f t h e road s h o u l d e r i n p e a t a r e a s , t h e m i n e r z l s o i l f i l l w a s pushed

I t i s c l e a r from t h e f i g u r e s t h a t t h e o r i g i n a l base under t h e road h a s s e t t l e d more i n t h e middle of t h e road and l e s s under t h e shoulder. I t can a l s o be observed t h a t t h i s tendency i s more pro- nounced on h i g h e r c l a s s r o a d s w i t h a g r e a t e r amount of t r a - f f l c .

For r e f e r e n c e , p h y s i c a l p r o p e r t i e s , p a r t i c u l a r l y t h e g r a i n s i z e of c o n s t r u c t i o n m a t e r i a l s are shown i n Table 1.4 and F i g . 1.5.

S o l 1 d i s t r i b u t i o n

P e a t a r e a s e x i s t extensive1.y i n t h e downstream a r e a of t h e I s h i k a r i River. However, 1 i t t l e i n f o r m a t i o n i s a v a i l a b l e on t h e s o i l d i s t r i b u t i o n a t lower d e p t h s and n o t h i n g d e f i n i t e i s Itnown, However, it may n o t be t o o f a r wrong t o c o n s i d e r t h e t e s t h o l e l o g s of t h e s i t e of t h e '.diusan Bridge (shown i n F i g . 1 . 6 ) and of t h e

s i t e of t h e T s u k l g a t a Bridge (shown i n F i g . 1 . 7 ) a s t y p i c a l of t h e s o i l p r o f i l e ( b o t h have been s u p p l i e d by t h e I s h i k a r i R i v e r Flood C o n t r o l O f f i c e of t h e Kokkaido Development Bureau). T h e r e f o r e , a t y p i c a l example g e n e r a l l y c o n s i s t s of a p e a t l a y e r o v e r 4

-

6 metres i n d e p t h , u n d e r l a i n by a deep, weak c l a y l a y e r ( i n some i n s t a n c e s measuring o v e r 20 rn). I n some c a s e s , sandy loam o r a sand l a y e r i s

found between t h e p e a t and c l a y l a y e r s ; i n o t h e r s , t h i n l a y e r s of p e a t o r sand a r e found i n s e v e r a l p l a c e s w i t k i n t h e c l a y l a y e r ,

t h e r e b y p r e s e n t i n g a r a t h e r complicated s t r a t i f i c a t i o n , Furthermore, a c c o r d i n g t o a n o t h e r s o u r c e ( 6 ) , a sedimentary f o r m a t i o n , which

c o n s i s t s mainly of sand o r sand and g r a v e l l a y e r s , e x t e n d s over 100 rn under t h i s c l a y l a y e r , and c l a y l a y e r s o r sandy c l a y l a y e r s of 5

-

15 m a r e found sandwiched i n i t . There i s no i n f o r m a t i o n on t h e d e g r e e of compaction,

O c c a s i o n a l l y a c o n s i d e r a b l e amount of c l a y e y sand o r sandy c l a y i s found mixed with t h e s u r f a c e l a y e r of p e a t t o a d e p t h of 1 0

-

30 cm. T h i s depends upon d r a i n a g e , t h e d e p t h t o t h e ground w a t e r l e v e l and f l o o d i n g from a d j a c e n t r i v e r s . However, g e n e r a l l y

t h e p e a t l a y e r i s a n accumulation o f v e g e t a b l e m a t t e r ; o n l y a

minute q u a n t i t y of c l a y e y s o i l s i s found i n i t ,

It a p p e a r s t h a t t h e depth t o t h e ground w a t e r l e v e l i s g e n e r a l l y 1 0

-

70 cm i n n a t u r a l

D e t a l l s of g e o t c c h n l c a l p r o p e r t i e s of t h e p e a t l a y e r w i l l be d i s c u s s e d l a t e r ; however, i t might be mentioned h e r e t h a t a n

i n c r e a s e i n s t r e n g t h w i t h d e p t h o r u n i l a t e r a l changes i n p r o p e r t i e s ( a s i s o f t e n observed i n an a l l u v i a l c l a y l a y e r ) , r a r e l y occur. When they do o c c u r , t h e y a r e observed t o be extremely rnlnute. T h i s i s q u i t e n a t u r a l i n a d e p o s i t c o n s i s t i n g mainly of t h e remains of v e g e t a b l e m a t t e r w i t h a s m a l l s p e c i f i c g r a v i t y . G e n e r a l l y speaking, t h e r e f o r e , t h e f a c t o r s which c o n t r o l g e o t e c h n i c a l p r o p e r t i e s of p e a t a r e thought t o be t h e q u a n t i t y of mineral m a t t e r i t c o n t a i n s and i t s d e n s i t y ( i n c l u d i n g a r t i f i c i a l compaction). Consequently, t h e r e are c a s e s , depending on t h e type of d e p o s i t , t h e q u a n t i t y of c l a y and d e n s i t y , i n which extremely weak i n t e r m e d i a t e l a y e r s a r e sandwiched. Furthermore, depending upon t h e p r o c e s s o f f o r m a t i o n , t h e r e i s a p o s s i b i l i t y of a c o n s i d e r a b l e d e g r e e of s u r f a c e v a r i a t i o n .

The c l a y l a y e r , which u n d e r l i e s t h e p e a t l a y e r , i s n o t a con- t i n u o u s c l a y l a y e r , a s was noted above. I n i t s upper l a y e r

e s p e c i a l l y i t h a s i n t e r s p e r s e d s e v e r a l l a y e r s of p e a t and e x t e n d s t o a sandy l a y e r w i t h v o l c a n i c a s h a t a depth of 20

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2 5 m. There i s a l s o a l a c k of i n f o r m a t i o n on t h e g e o t e c h n i c a l p r o p e r t i e s of t h i s c l a y l a y e r .

That p o r t i o n of t h e road which comprises t h e f o u n d a t i o n , t h e p e a t , i s c l e a r l y compressed and t h a t p o r t i o n of t h e o v e r l y i n g road

i s depressed. T h i s i s b e t t e r understood by examining Fig. 1.4, t h e c r o s s - s e c t i o n d i a p a m , and t h e d i s t r i b u t i o n of g e o t e c h n i c a l proper- t i e s a g a i n s t d e p t h , which w i l l be d e a l t w i t h l a t e r . ' d i t h i n t h e

scope of t h e e x t e n t and composition Of r o a d s which were i n v e s t i g a t e d h e r e , one may t h i n k of t h e a f f e c t i v e range t o be w i t h i n t h e range of t h e p e a t l a y e r . However, t h i s must be r e c o n s i d e r e d s e p a r a t e l y with r e s p e c t t o f u t u r e t r a f f i c c o n d i t i o n s , t o t h e c o r r e s p o n d i n g con-

s t r u c t i o n , and t o t h e n e c e s s a r y maintenance and o p e r a t i o n . D i s t r i b u t i o n of ~ e o t e - ~ k n _ i c a l ~ q o m i e s a,z%inst d e 9 1

From t h e d a t a obtainocl a t t h e s i t e s of g e n e r a l i n v e s t i g a t i o n s , t h e s o i l p r o f i l e , t h e d e p t h . t o ground water l e v e l , p e n e t r a t i o n

a r e summarlzed and shown In P I g. 1.9.

These w i l l i n d i c a t e t h e p r o p e r t i e s of t h e p e a t l a y e r i n t h i s d i s t r i c t . For i n s t a n c e , t h e vane s h e a r values, g e n e r a l l y speaking,

a r e 0.05

-

0.25 kg/cm2 i n a p e a t a r e a such a s Ohuokakusan. Values l i e mainly i n t h e neighbourhood of 0.1 kg/cm2. Even i n t h e c a s e of t h e Kitamura Land Improvement Area, which i s l o c a t e d a d j a c e n t t o t h e main stream of t h e I s h i k a r i River and i s i n a r e l a t i v e l y b e t t e r

c o n d i t i o n , t h e v a l u e s measure 0.2

-

0.3 kg/cm2. It h a r d l y needs t o be ss.id t h a t i n p l a c e s where p e a t i s compressed by dykes and r o a d s , o r where m i n e r a l m a t t e r i s found i n g r e a t q u a n t i t y , t h e value

i n c r e a s e s .

Since i t c o n s i s t - s rnainly of v e g e t a b l e m a t t e r , p e a t d e n s i t y i s extremely low

-

t h e v a l u e b e i n g approximately 1 g-/cm3. The water c o n t e n t i s e x t r e ~ n e l y h i g h , with t h e water c o n t e n t r a t l o b e i n g approximately 3

-

10. The d r y d e n s i t y ranges between 0.08 t o 0.25 g/cm3. G e n e r a l l y , we may r e g a r d it t o be 0 . 1

-

0.2 g/cm3.

The value i s i n f l u e n c e d by t h e m i n e r a l c o n t e n t . Thus, measurements were made w i t h t h e e x p e c t a t i o n t h a t i n a p e a t l a y e r t h e i g n i t i o n l o s s o r t h e i g n i t i o n r e s i d u e would f u r n i s h a means of a s s e s s i n g i t s p r o p e r t i e s . The v a l u e s were 50

-

95%; and i t was r e a l i z e d t h a t p e a t was e x t r a o r d i n a r i l y d i f f e r e n t frorrl o r d i n a r y s o i l .

I n p e a t , c o n s i s t i n g mainly of decomposed o r g a n i c m a t t e r , which i s s o f t , t h e r e must be c l o s e c o r r e l a t i o n between such f a c t o r s a s d e n s i t y , w a t e r c o n t e n t , amount of o r g a n i c matter, and s h e a r s t r e n g t h . These r e l a t i o n s h i p s and s p e c i a l c h a r a c t e r i s t i c s have a l r e a d y been p u b l i s h e d i n p a r t i n a p r e v i o u s r e p o r t ' ' ) . I t i s planned t h a t a f u r t h e r r e p o r t on t h i s s u b j e c t w i l l be forthcoming.

G e n e r a l l y i t i s assumed t h a t t h e r e l a t i o n s h i p between t h e p e n e t r a t i o n index ( F ) by cone penetrometer and t h e vane s h e a r ( s ) c a n be e x p r e s s e d a s I?

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10 S. To determine t h e a p p l i c a b i l i t y of t h i s r e l a t i o n s h i p i n t h e c a s e of a p e a t l a y e r , t h e v a l u e s of t h e p e n e t r a t i o n i n d i c e s and t h o s e of t h e vane s h e a r , were o b t a i n e d from t h e d e p t h d i s t r i b u t i o n i n Fig. 1 . 8 and Ivere recorc?ed t o g e t h e r i n P i g . 1 . 9 . An examination of t h e f i g u r e shows t h a t t h e r e l a t i o n s h i p

i s approximately t r u e . The r e s u l t s of i n v e s t i g a t i o n s on many v a l u e s observed by t h e a u t h o r and o t h e r s (') s u p p o r t t h e a p p l i c a b i l i t y of t h i s r e l a t i o n s h i p . T h i s s u b j e c t w i l l a l s o be d i s c u s s e d i n a l a t e r r e p o r t . I n o r d e r t o study t h e i n f l u e n c e of e x i s t i n g r o a d s on t h e geo- t e c h n i c a l p r o p e r t i e s of t h e p e a t f o u n d a t i o n , d a t a from t h e c e n t r e o f t h e road and n a t u r a l ground R - 2 1 . 8 rn Chuokakusan were e x t r a c t e d

from Fig. 1.8.1 and sketched i n Fig. 1.10. A s t u d y o f t h e f i g u r e shows marked v a r i a t i o n s i n t h e p e n e t r a t i o n i n d e x and t h e vane s h e a r f o r a c o n s i d e r a b l e depth. On t h e o t h e r hand, i t a p p e a r s t h a t t h e r e a r e d i f f e r e n c e s i n t h e q u a l i t y of t h e p e a t b a s e l a y e r as observed from t h e i g n i t i o n l o s s . Thus, i t i s impossible t o a t t r i b u t e t h e s t r e n g t h v a r i a t i o n s t o t h e e f f e c t of t h e r o a d , from t h i s evidence a l o n e . It i s d i f f i c u l t t o make q u a n t i t a t i v e a n a l y s e s a t o t h e r s i t e s . I n o r d e r t o confirm t h i s , i t . w o u l d be n e c e s s a r y t o make continuous o b s e r v a t i o n s on t h e q u a n t i t y and t h e q u a l i t y o f s e t t l e m e n t and t h e d i s t r i b u t i o n through d e p t h even p r i o r t o c o n s t r u c t i o n of t h e road

t o s t u d y changes i n c h a r a c t e r i s t i c s of c o n s t r u c t i o n m a t e r i a l s by l a b o r a t o r y t e s t s on u n d i s t u r b e d samples, and t o a n a l y z e t h e c o r r e l a - t i o n between t h e two.

( 5 ) C o e f f i c i e n t of b e a r i n g c a p a c i t x

When a r o a d , e x p e c i a l l y a paved r o a d , i s b u i l t on a weak f o u n d a t i o n such as p e a t , i n a d d i t i o n t o t h e amount and r a t e of

s e t t l e m e n t , t h e f u n c t i o n a l behaviour of t h e body of t h e road

-

which i s a s u p p o r t i n g s t r u c t u r e f o r dynamic t r a f f i c l o a d s

-

on a p e a t

l a y e r must be determined as a m a t t e r of fundamental importance. I n view of t h e c h a r a c t e r i s t i c s of t h e p e a t f o u n d a t i o n , and i n accord- ance w i t h t h e t r a f f i c l o a d s , t h e q u a l i t y and t h e s i z e of t h e road s t r u c t u r e must be determined.

The problem of s e t t l e m e n t can be regarded as similar t o t h e problems encountered i n o t h e r s t r u c t u r e s such a s r i v e r dykes. However, dynamic p r o p e r t i e s of a road must be i n v e s t i g a t e d

thoroughly and s e p a r a t e l y a l o n g w i t h i n v e s t i g a t i o n s of such m a t t e r s as t h e q u a l i t y and t h e s t r u c t u r e of t h e pavement.

A s a pYeliminary measure i n o b t a i n i n g a n answer t o t h e s e problems, p l a t e b e a r i n g t e s t s were conducted. These were c a r r i e d o u t a t f o u r p l a c e s (No. 6

-

9 ) near Tobetsu-Machi on t h e Sapporo- Numata r o u t e , a s h a s been e x p l a i n e d i n t h e s e c t i o n d e a l i n g with "Routes and s i t e s of i n v e s t i g a t i o n " , S e c t i o n 1 ( I ) , i n a d d i t i o n

t o

!'General i n v e s t i ~ a t i o n s i t e s No. 1

-

5 " , which have been t h e l o c a t i o n s o f t h e I n v e s t i g a t i o n s t h u s far.

The method used was explained i n S e c t i o n 1 ( 2 ) . Measurements were made n o t o n l y a t t h e road s u r f a c e b u t a l s o a t each c o n s t i t u e n t l a y e r . Thus i t would be p o s s i b l e t o o b t a i n some measure a t l e a s t of t h e s t a t i c b e a r i n g c a p a c i t y of each l a y e r which c o n s t i t u t e s t h e road s t r u c t u r e .

Fig. 1.11 shows diagramatically t h e r e s u l t s of t h e s e measure- ments, t o g e t h e r with r e l a t e d data. I n o r d e r t o o b t a i n t h e r e l a t i o n - s h i p between t h e load ( q ) , t h e s e t t l e m e n t (w), and t h e b e a r i n g

c a p a c i t y c o e f f i c i e n t , t h e r e l a t i o n s h i p s between q/w and w and q

were drawn up. This i s shown i n F i g . 1.12.

E v a l u a t i o n of t h e b e a r i n g c h a r a c t e r i s t i c s of a road by t h e so- c a l l e d K-value i n v o l v e s t o o many problems; i t i s f e l t t h a t i t i s i r r a t i o n a l t o depend upon t h e o r d i n a r y K-value method, e s p e c i a l l y i n t h e c a s e of a weak l a y e r such as p e a t , An examination of

measured v a l u e s does n o t i n d i c a t e a l i n e a r r e l a t i o n s h i p between q

and w except i n t h e s u r f a c e of t h e g r a v e l l a y e r . T h e r e f o r e , i n t h e p r e s e n t s t u d y i t was decided t o e x p r e s s t h e K-value as an e x t r a - p o l a t e d value of q/w a t w ( o r q ) = 0 from t h e r e l a t i o n q / w

-

w

( o r q ) , The d i s t r i b u t i o n of K-value a g a i n s t t h e depth of each l a y e r

t h u s determined i s sulnmarized i n Table 1.5 and Fig. 1.13. Since t h e r e i s a s l i g h t displacement h o r i z o n t a l l y between t h e s i t e of t h e p r e s e n t i n v e s t i g a t i o n and t h e s i t e of t h e road d e s c r i b e d i n S e c t i o n

2 ( 2 ) (where t h e i n v e s t i g a t i o n on t h e road composition w a s made), t h e r e are minor d i f f e r e n c e s i n d e t a i l i n t h e composition of t h e l a y e r s . I n t h e p r e s e n t investigation, f o r convenience of t e s t l o a d i n g , i n many c a s e s t h e l o a d i n g p l a t e of @ = 3 0 cm was used f o r

L i t t l e i s known r e g a r d i n g t h e r e l a t i o n s h i p o f K-value t o t h e d i f f e r e n c e i n p l a t e d i a m e t e r used f o r e a c h l a y e r

-

one example, however, b e i n g t h a t made i n f r o n t

of

t h e Kitamura Land Improvement O f f i c e . T h e r e f o r e , t h e K,,

t o

K,, c o n v e r s i o n c o e f f i c i e n t was

c o n s i d e r e d

t o

be 30/50 = 0.6; t h o s e v a l u e s c o r r e s p o n d i n g t o

4

= 30 c m were c o n v e r t e d t o $ = 50

cm.

These are t h e v a l u e s which are shown. The r a n g e o f K-values f o r e a c h l a y e r w i l l be known from t h e s e

f i g u r e s . (It i s n e c e s s a r y t o r e a l i z e t h a t t h e method o f d e t e r m i n i n g t h e amount

of

s e t t l e m e n t i n t h e c a l c u l a t i o n o f K-values i s d i f f e r e n t from t h e o r d i n a r y method.)

The r e s u l t s ( 3 ) o f similar t e s t s , which h a v e been conducted o n p e a t i n t h e v i c i n i t y of Miuta and i n d e p e n d e n t l y

of

t h e p r e s e n t

i n v e s t i g a t i o n s , were t r e a t e d i n t h e same way as d e s c r i b e d above. These are shown i n F i g . 1.14. These i n v e s t i g a t i o n s i n d i c a t e t h a t

t h e K-values d e t e r m i n e d by t h i s method a r e a p p r o x i m a t e l y 0.15 k&em3 w i t h t h e $ = 50 c m p l a t e . I n t h e case o f a 20 c q sand l a y e r on t o p o f t h e p e a t , t h e K-value i s a p p r o x i m a t e l y 0.45 kg/cm3. A s t h e r e i s n o i n f o r m a t i o n on t h e t y p e and t h e c o n d i t i o n o f t h e p e a t l a y e r i n t h i s s i t e , d i r e c t comparison may n o t be v a l i d . However, d a t a a r e a d e q u a t e

t o

i n d i c a t e t h a t t h e p e a t l a y e r u n d e r t h e e x i s t i n g r o a d i s w e l l c o n s o l i d a t e d . L e t u s assume t h a t B u r m i s t e r t s t h e o r y ( 4 ) c o n c e r n i n g a d o u b l e - l z y e r e d e l a s t i c body a p p l i e s t o t h e p r e s e n t c a s e . By c a l c u l a t i n g t h e v a l u e s c o r r e s p o n d i n g t o t h e modulus o f e l a s t i c i t y ( E ) o f t h e u p p e r l a y e r on t h e basis o f such f a c t o r s a s i t s t h i c k n e s s , t h e c o e f f i c i e n t o f b e a r i n g c a p a c i t y a t t h e s u r f a c e o f t h e u p p e r l a y e r , and t h e s i z e

of

t h e l o a d i n g p l a t e , t a k i n g t h e measured v a l u e s o f t h e c o e f f i c i e n t of b e a r i n g c a p a c i t y a t e a c h l a y e r as t h e c o e f f i c i e n t o f b e a r i n g c a p a c i t y a g a i n s t t h e lower l a y e r s , w e o b t a i n t h e v a l u e s shown i n t h e l a s t column o f T a b l e 1.5. An e x a m i n a t i o n o f t h e v a l u e s i n d i c a t e s t h a t t h e E-value (Irg/cm2) o f a p e a t l a y e r v a r i e s w i t h such f a c t o r s a s t h e c o m p o s i t i c n and t h e d e g r e e of c o n s o l i d a t i o n of p e a t . I n t h e p r e s e n t i n v e s t i g a t i o n s , v a l u e s r a n g i n g from 9 t o 680 kg/cm2 were o b t a i n e d . A s t h e v a l u e s f o r t h e lovcer p e a t l a y e r

e s p e c i a l l y i n d i c a t e ,

E

becomes 13

-

36 kg/cm2 a.t 20

-

30 cm below t h e upper s u r f a c e of t h e p e a t l a y e r , which i s compressed by t h e e x i s t i n g r o a d , e x h i b i t i n g a s h a r p d e c l i n e w i t h i n c r e a s e i n depth. These v a l u e s a r e observed t o be much lower than i n g r a v e l o r compressed m i n e r a l s o i l l a y e r s .

It would be convenient i f t h e c o e f f i c i e n t o f b e a r i n g c a p a c i t y

( K

= (q/wIw = ) could be e s t i m a t e d from t e c h n i c a l c h a r a c t e r i s t i c s which could be o b t a i n e d by a s i m p l e r method. T h e r e f o r e , d a t a were r e a r r a n g e d i n F i g . 1.15 t o exarnlve t h e r e l a t i o n s h i p between t h e p e n e t r a t i o n index and t h e vane s h e a r , I n t h e f i g u r e , t h e r e l a t i o n -

s h i p &tween t h e K-value f o r p e a t l a y e r s i n each p l a c e shown i n Table 1,15 and t h e average value a t each d e p t h f o r t h e p e n e t r a t i o n index ( P ) o r t h e vane s h e a r ( V ) a t 50 cm and 100 cm below t h e

s u r f a c e of t h e l a y e r i s i n d i c a t e d . The d i s t i n c t i o n between t h e upper and t h e lower l a y e r s r e f e r r e d t o h e r e correspond t o t h o s e

shown i n t h e column on " s o i l type" i n Table 1,15.

The f i g u r e does n o t i n d i c a t e a c l e a r r e l a t i o n s h i p between t h e two, The K-values ( w i t h t h e e x c e p t i o n of t h a t f o r t h e f r o n t of t h e Kitamura Land Improvement Area No. 4 s i t e ) l i e i n a r e l a t i v e l y

narrow range

-

C.6

-

1 kg/cm3 i n t h e upper l a y e r and 0.4

-

0 , 5 kg/cm3 i n t h e lower l a y e r . It would appear t h a t t h e p a r t i c u l a r l y l a r g e value f o r t h e Kitamura s i t e i s due t o t h e l a r g e amount of min e r a 1 s o i l . Although t h e p e n e t r a t i o n i n d i c e s vary only s l i g h t l y between t h e upper and t h e lower l a y e r s a t each s i t e , t h e r e are

d i f f e r e n c e s i n t h e K-values, This i n d i c a t e s t h a t a l t h o u g h t h e r e i s n o t much d i f f e r e n c e i n t h e d e s t r u c t i v e c o n d i t i o n s compared w i t h t h o s e f o r t h e cone penetrometer when viewed i n t h e l l g h t of t h e r e l a t i o n s h i p with t h e amount of i n i t i a l s e t t l e m e n t , movement c h a r a c t e r i s t i c s become c o n s i d e r a b l y d i f f e r e n t . I n t h e p r e s e n t

i n s t a n c e , f o r d e p t h s of 50 c a and 100 cm t h e r e i s l i t t l e d i f f e r e n c e i n v a l u e s of P and V. T h i s i n d l c a t e s t h a t i n t h e c o n t e x t of t h e experimental vethod t h e y a r e approximately t h e same,

T h i s d e s c r i p t i o n h a s been merely a c o n s o l i d a t i o n of t h e

t h e b e a r i n g c a p a c i t y of each l a y e r can be determined, However, t h e a u t h o r wishes t o d e f e r t h i s u n t i l t h e r e s u l t s o f o t h e r s e p a r a t e l y conducted i n v e s t i g a t i o n s a r e made known. I n any c a s e , t h e a u t h o r b e l i e v e s t h a t a f u l l i n v e s t i g a t i o n needs t o be made o f t h e dynamic p r o p e r t i e s o f a p e a t l a y e r t o r e s i s t dynamic t i k f f i c l o a d s , . as w e l l as of t h e road s t r u c t u r e . Conclusions As was e x p l a i n e d a t t h e o u t s e t , t h e p r e s e n t i n v e s t i g a t i o n s were c a r r i e d o u t a s a f i r s t s t e p i n t h e s o l u t i o n ' o f problems on r o a d s i n p e a t a r e a s . It can be s a i d t k a t t h e s e i n v e s t i g a t i o n s have c o n s i d e r a b l y c l a r i f i e d t h e g e o t e c h n i c a l c o n d i t i o n s i n r o a d s and f o u n d a t i o n s i n p e a t a r e a s ; f u r t h e r , t h e y have given r i s e t o s e v e r a l new problems.

I n o r d e r t o study t h e mechanism of compression of t h e f o u n d a t i o n under t h e road s t r u c t u r e , a n a l y s e s were attempted on d e n s i t y

d i s t r i b u t i o n , t a k i n g i n t o account t h e composition of t h e foundation. No d e f i n i t e c o n c l u s i o n could be drawn. The main r e a s o n f o r t h i s can be a t t r i b u t e d t o t h e l a c k of d a t a on i n i t i a l c o n d i t i o n s . I t can be

s a i d t h a t very l i t t l e i s known concerning t h e mechanism of s u p p o r t a g a i n s t dynamic l o a d s , It w i l l be n e c e s s a r y t o i n i t i a t e new

i n v e s t i g a t i o n s i n t o t h i s s u b j e c t .

I t h a s been p o s s i b l e i n t h e p a s t t o o b t a i n g e o t e c h n i c a l d a t a on t h e p e a t l a y e r i n connection with such p r o j e c t s as r i v e r dykes. However, t h e a u t h o r ' s knowledge of t h e methods o f g e o t e c h n i c a l i n v e s t i g a t i o n of p e a t a r e a s and t h e p r o p e r t i e s o f p e a t a r e a s has been widened c o n s i d e r a b l y a s t h e r e s u l t of t h e p r e s e n t i n v e s t i g a - tions. T h i s h a s been one of t h e major o b j e c t i v e s of t h e i n v e s t i g a - t i o n . F u r t h e r o b s e r v a t i o n s w i l l be p u b l i s h e d i n a l a t e r r e p o r t .

The p r e s e n t study owes much t o s u g g e s t i o n s and a d v i c e of Prof. Sanai of Hoku-Dai, M r . Takahashi, D i r e c t o r o f t h e C o n s t r u c t i o n D i v i s i o n of t h e Development Bureau, and M r . Ifukube, t h e D i r e c t o r of t h e C i v i l Engineering Research I n s t i t u t e . I n a d d i t i o n , i n t h e a c t u a l i n v e s t i g a t i o n s , c o o p e r a t i o n h a s been g i v e n by M r . Ohira

t

members of the Dyke Research Institute. In addition a part of the investigation, such as the plate loading test, was carried out with the assistance of sta.ff members of the Road Research Institute. We would also like to express our appreciation for the assistance

1. Miyakawa, Lsamu. G e o t e c h n i c a l i n v e s t i g a t i o n s of r i v e r dykes i n p e z t a r e a s . I n t e r m e d i a t e r e p o r t , 1 0 t h Meeting of t h e T e c h n i c a l Research Group i n t h e K i n i s t r y of C o n s t r u c t i o n . Nov. 1956. C i v i l E n g i n e e r i n g Research I n s t i t u t e L a b o r a t o r i e s , Holckaido Developnient Bureau. G e o t e c h n i c a l i n v e s t i g a t i o n of p e a t a r e a s (Development and I n v e s t i g a t i o n Branch, FIokkaido Development Bureau, March 1957).

M i yakawa, Iscarnu. On s o i l c l l a r a c t e r i s t i c s of p e a t a r e a s . Monthly R e p o r t , C i v i l E n g i n e e r i n g Research I n s t i t u t e , Hokkaido Development Bureau. J u l y , 1957.

2. O h i r a , Shitoku. hxarnples of i n v e s t i g a t i o n s on e x i s t i n g r o a d s i n p e a t a r e a s and c a r e on h a n d l i n g of p e n e t r z t i o n t e s t equipment. F i r s t T e c h n i c a l Study Group PIeeting, Hol-:kaido Development Bureau. Feb. 2 8 , 1956.

3 . Development and I n v e s t i g a t i o n Branch, Iio!.rkaido Development Bureau. S t e e l Ma.t Road T e s t . Ma-rch, 1955.

4. B u r m i s t e r , P.M. The t h e o r y of s t r e s s e s and d i s p l a c e m e n t s i n l a y e r e d systems and a p p l i c a t i o n s t o t h e d e s i p of a i r p o r t runways. Froc. Highway Res. Board, ;.*/ashington, 2 3 : 126-

1 4 1 , 1943.

5. Dyke Study I n s t i t u t e , C i v i l E n g i n e e r i n g Research I n s t i t u t e , Hokkaido Cevelopment Bureau. Isamu lL!l yakawa and H i r o s h i Yarnaga. I n v e s t i g a t i o n s and t e s t s on fouridat.ion of new waterway of Kyu Toyohirz. 3 i v e r dyke ( i n t e r m e d i a t e r e p o r t ) . 3 u b l i s h e d by I s h i l ~ a r i Hiver Conservation O f f i c e , March, 1954.

A s above: Geotechnica.1 i n v e s t i g a t i o n s of r i v e r dykes i n p e a t a r e a s . 9 t h Meeting of T e c h n i c a l Research Group i n t h e M i n i s t r y of C o n s t r u c t i o n , J u l y 1955, and Report No.14, Oct. 1955.

Ibqiyakawa, Isamu and O h i r a , Shltoku. S t a b i l i t y of dykes i n p e a t a r e a s and o t h e r problems. C i v i l Z n c i n e e r i n g S c c i e t y 1 1 t h meeting, May, 1955.

6. For i n s t a n c e : Miyalcawa, I'itagawa, Abe

,

and Matsurnoto. S t a b i l i t y of road mound i n weak p e a t a r e a s . C i v i l Xngineering Research I n s t i t u t e , Eokkaido Development Bureau, 1957.

Table 1.1 S i t e s and r o u t e s of i n v e s t i g a t i o n S i t e s of g e n e r a l i n v e s t l g s t i o n s S i t e s of p l a t e b e a r i n g t e s t No 1 2 3 4 5 6 7 8 9 Names of s i t e s V i c i n i t y of Chuokakusan ( p o i n t of i n t e r - s e c t l o n of new c a n a l with Kyu Toychira River)

V i c i n i t y of Daihaisui ( p o i n t of i n t e r - s e c t i o n of Shinotsu Canal)

Near Shinot su Canal Off i c e , Sapporo 3evelopment and Construction Div., Development Bureau

I n f r o n t of Kltamura Land Improveaent D i s t r i c t O f f i c e

Near i n t e r s e c t i o n of Shinotsu Canal

Setwsen r o u t e KO. 27 and 28, Ebstsu-

Machi ( 7 m towards Ebetsu from t h e

puxping s t a t i o n )

I s h i k a r i Tobet su-Yachi r o u t e No. 5

( 4 8 m towards Zbetsu)

I s h i k a r i Tobetsu-?iachi, Nishiura (160 rn towards Zbetsu from the f i r e - b e l l )

I n t e r s e c t i o n of Kanazawa S t a t i o n S t r e e t ( 9 m towards Tobetsu) Route type Primary l o c a l road I I P r e f e c t u r a l road I I T o ~ m - v i l l a g e road Primary l o c a l road I I I I I I Kame of r o u t e Sapporo-?Jumata r o u t e I I Tobetsu-Kamihorornui S t a t i o n 2oute I I Tobetsu-Machi r o u t e

NO. 32, south NO. 5

Sappcro-Nunata r o u t e

I I

I I

T a b l e 1.2

An example o f r e s u l t s of i n v e s t i s t i o n o f amount o f t r a f f i c

on

Sapporo-Kumata r o u t e , a p r i m a r y l o c a l r o a d

Date: Average o f S e p t . 27 and 2 8 , 1 9 5 5

From 7 a.m. t o 7 p.m.

-

12 h o u r s S i

t e

_{v e h i c l e} Slow Nsebo r a i l w a y c r o s s i n g L e f t bznk o f K a r i k i b a s h i Z n t r a n c e

t o

Tobe t su-Xachi Shack i n Tobetsu-?lachi S t r e e t o f Urausu-Xura S p e c i a l v e h i c l e Kotor car 3 , 9 3 1 254 734 2 1 1 581 A 1

-

-

-

-

S u b - + , o t a l 1 , 6 7 3 463 6 4 5 246 389 P a s s e n g e r v e h i c l e 300 9 5 72 1 9 9 6 Trucgs 1 , 3 7 3 368 5 7 3 227 2 9 3

T a b l e 1.4 C h a r a c t e r i s t i c s o f m a t e r i a l c o m p r i s i n g g r a v e l r o a d s

No.

d e n s i t y Dry ( g/cm3

1

1 , E O 1 . 5 1 1 , 2 3 1.69 1 , @ 4 P l a c e M o i s t u r e

content

($1

6 , 4 27 4 3 1 5 59 1 C o n s i s t e n c y L o e a t i o n o f s a m p l e s Chuokakusan

-

L.L G r a n u l a r c o m p o s i t i o n (

$1

S l a c e C e n t r e II II n n rr 24 32 1.26 I G r a v e l 38 8 5 5 Oepth 0- 8 8-20 20-32 32-64 64-82 82-113 56 1 9 2 3 5 1 27 49 6 0 1 9 4 1 2 3 31 25 t P.L 0-16 16-28 28-39 2 2 , 2 9 5 9 P . 1 Sand 28 27 7 0 1 2 37 1 7 12

1

I

29 50 4 0 3 0 3 0 36 52 8 1 6 29 34 2 5 I 3 4 5 D a i h a i s u i 1 4 22 49 7 0 S i l t 22 47 13 6 6 6 6 5 Centre II 11 3 5 48 2.09 1.52 1.38 C l a y 1 2 26 9 22 2 18 6 6 34 5 2 37 4 46 50 2 5 2 1 2 7 I I n f r o n t o f t h e C a n a l O f f i c e 56 49 I 7 24 26 1 4 1 7 26 1 6 8 8 3 46 34 2 3 1 4 2 3 I 9 -18 I C e n t r e II n 3 0 3 0

I

s o u t h NO. 5

,

l o E 9 1.78 1.38 0-25 25-33 3,739 26 1 9 I 2 1 18 2 1 I 0- 6 6- 18 24-38 O w l 0 0 - 9

t

i

I n f r o n t o f Kitarnura Land I m 7 r o v e r e n t C f f i c e Tobe t su-l-:achi town r o u t e No. 32, Centre tl II Centre L 1 8 m I1

T a b l e 1.5 R e s u l t s o f p l ~ t e b e a r i n g t e s t

-

NO. -. 1 -. 2 -. 3 -. 4 P l a c e Chuokakusan D a i h a i s u l I n f r o n t o f C a n a l O f f i c e I n f r o n t o f X i ta-iqura L a n ~ Improvemel:', Off i c e D e p t h (cm) S o i l t y p e U n s c r e e n e d g r a v e l l a y e r C l a y l a y e r G r a v e l l y c l a y l a y e r C l a y l a y e r P e a t l a y e r U n s c r e e n e d g r a v e l l a y e r C l a y l a y e r P e a t ( u p p e r l a y e r ) P e a t ( l o w e r l a y e r ) U n s c r e e n e d p a v e 1 l a y e r C l a y m i x e d w i t h f i n e p a v e 1 l a y e r P e a t ( u p p e r l a y e r ) F e a t ( l o w e r l a y e r ) U n s c r e e n e d g r a v e l l a y e r P e a t ( u p p e r l a y e r r e n t ( l o w e r l i i y e r ) S t r a t i f i c a t i o n o f l a y e r s b e l o w t h e t e s t s u r f a . c e G r a v e l 8 cm. C l a y 1 2 cm. Send 1 2 cm. C l a y 3 2 cm. G r n v e l l l y c l a y 18 cm. C1.ay 31 cm. Peat; 5 m l o a d i n g C o n s i s t s o f l a y e r s b e l o w c p a v e l l y c l a y i n t h e f i r s t s e c t i o n

I

C o n s l s t s o f l a y e r s b e l o w t h e s e c o n d c l a y l a y e r ( s h o w n b y - l i n e i n t h e f i r s t c o l u m n ) C l a y 31 om. Perit 5 cm

1

5 0 5 0 P e a t 6 6 cm. V o l c a n i c a s h 3 cm. F e a t l a y e r b e l o w Grtrvel 1 9 cm. C l a y 2 0 cm.

Sandy loam mixed w i t h f i n e &ravel 6 cm. P e a t 4 cm C o n s i s t s o f l a y e r s b s l o w c l a y l a y e r shown i n t h e f i r s t s e c t i o n a b o v e G r a v e l l y p e a t 13 cm. I V o l c a n i c a s h 4 cm. P e a t 4 m P e a t l a y e r

1

50 G r a v e l 26 cm. C l a y mixed w i t h f i n e , u r a v e l 24 cm. C l a y mixed w i t h f i n e r ~ r a v e l 24 cm. P e a t 4 m 1 P e a t 4 m

1

50 F e a t l a y e r

1

50 G r a v e l 1 0 c a . C l a y 1 0 cm. G r a v e l l y c l a y 5 cm. C l a y 1 0 cm. P e a t 2 0 cm. V o l c a n i c a s h 3 cm. P e a t P e a t 20 cm. V o l c a n i c a s h 3 cm. F e a t 5 . 7 m

T a b l e 1 . 5

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C o n t i n u e d P l a c e D e p t h Tobetsu-Mach1 0 5 r o u t e No. 3 2 , s o u t h No. 5 2 3 I s h l k a r i i: ;: i: ui :: :; i

1

;:

6 o f Kannzawa S t a t i o n S t r e e t

1

64 E b e t su-Machi b e t w e e n r o u t e s 2 7 a n d 2 8 8

-

2 1 cm. V o l c a n i c cm. P e a t 3.6 m 3 0 2.4 2 8 0 7 0 P e a t ( u p p e r l a y e r ) P e a t 3.6 rn

_-

1

3 0

)

0 . 3 1 0.09

_-

I s h l k a r i Tobetsu-Machi, N i s h i u r a 0 4 6 P e a t ( u p p e r l a y s r )

I

p e a t l a y e r

1

50

1

0.51 U n s c r e e n e d g r a v e l 3 3 cm. C l a y e y s a n d 1 6 cm. C l s y e y U n s c r e e n e d G r a v e l 2 0 cm. C l a y 1 7 cm.

1

30

1

9.4 g r a v e l l a y e r Humus 3 3 cm. F e a t l a y e r Unscrsened layer l a y e r layer C o n s i s t s o f i t e m s b e l o w c l a y i n t h e f i r s t s e c t i o n

1

50

(

1.3 l o r n 7 cm. Hurnus 11 cm. V o l c a n l c a s h 3 cm. C l a y 44 cm. P e a t l a y e r below C l a y 4 4 cm a n d ? e a t l a y e r below P e a t l a y e r P e n t l a y e r C l a y l a y e r ! c l a y l a y e r 5 0 2 - 8 -

--

3 0 50 Unscreened layer 5 0 G r a v e l 34 cm. G r a v e l l y c l a y 6 cm. Humus 6 cm. C l a y l a y e r below

I

3 0

/

9.8

I

C l a y 33 cm. P e a t l a y e r c l a y l a y e r below

1

50

1

6.0 8 . 6 , 9.6 1.3 0.36 Unscreened gravel layer P e a t ( u p p e r l a y e r 1

I

P e a t l a y e r

1

50

/

1.3 7 . 7 1.1 U n s c r e e n e d , ~ a v e l 2 0 cm. C l a y e y g r a v e l 5 cm. C l a y

1

3 0

/

8.3 3 3 cm. P e a t l a y e r F o o t n o t e s : 1. B e a r i n g c a p a c i t y l n d e x q/w was c o n v e r t e d t o l o a d l n g p l a t e d i a m e t e r o f 50 cm. 2. The numbers c o r r e s p o n d t o t h o s e o f T a b l e 1.1.

EL

l a y e r ) P e a t l a y e r

I

5 0 1 0 . 5 8

F i g . 1.1 Roads and p l a c e s i n v e s t i g a t e d I s h i k a r i Bay To t h e C i t y o f O t a r u T o y o h i r a R i v e r Kyu I s h i k a r i R i v e r S a s s h o r o u t e Hiroshima-Mura ( v i l l a g e ) S e n z a i R i v e r S h i n o t s u Canal E b e t s u R i v e r I s h i k a r i R i v e r C i t y o f Iwamizawa Horonai r o u t e Town o f Hayama Y u h a r i R i v e r Ilakodate main r o u t e C i t y of Sapporo T e i z a n k e i Railway I s h i k a r i R i v e r Iiakodate main r o u t e S e n z a i r o u t e Town o f T o b e t s u C i t y o f E b e t s u Y u h a r i Railway IIakodate main r o u t e To C i t y o f Miuta Manji r o u t e Y u h a r i r o u t e Muroran main r o u t e

G e n e r a l conditri.on and i t e m s investigated

a t s i t e s o f g e n e r a l i n v e s t i g a t i o n

No. 1 Main r o a d , Sapporo-Numata r o u t e , i n t h e v i c i n i t y o f new c a n a l a t Chuokakusan D r a i n a g e pr, D r a i n a g e m

s

~ 3 1 . 8 ~ ~ 7 . 0 ~ ~ 3 . 6 ~ ~ 2 . 3 ~

. . .

! ~ 2 . ~ ~ ~ 4 . 1 ~ R 5 . 3 ~ ~ 8 . n n

.

~ 1 1 . 3 "

.

~18.0" R2$.8"

. . .

.

.

D o D C O D 0 0 I 1 I I I I - ... - 3 1;---;.

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.. . . . . .+. -. . . . . ,"",,, " - 8 , ' I i . I I , I c f 8 - P.5. 0 6 - 3 5 . I I I 4 ' 3. 2 . 1 . 0. P e a t 0 0 / # I / I I I I I * . 1 1 , - .----~. I I ... - - f . i ~. ... ~~'...' , Y l l l $ 8 , ! -.,.. ...-... _{t-- I "} ' . . ~ 1 i I I I I 1 1 I I i i I ! I P e a t ___--- -- - - -. Clay %Vane t e s t A P e n e t r a t i o n t e s t - I - I Clay Vane t e s t P e n e t r a t i o n t e s t 0 Water l e v e l mea.surement h o l e ----Ground water l e v e l 0 Ground w a t e r l e v e l measurement h o l e ---- Ground w a t e r l e v e l ---Volcanic a s h ( s a n d )

Fig.

1.3

-

continued

No.

I x

Vane test

'lay A

penetration test

o

Ground water level measurement hole

-.--

Ground water level

---Volcanic ash (sand)

No.

3

Main road, Tobetsu-Kamihoromui Station route,

I n

front of Shinotsu Canal Office

I

I

--- . --

Peat

Clay

x

Vane

__f_

test

A

Penetration test

o

Ground water level measurement hole

....-

Ground water level

---Volcanic ash (sand)

4

Prefectural road, Tobetsu-Kamihoromui Station, in front of

F i g .

1.3

-

c o n t i n u e d

No.

5

Town and v i l l a g e r o a d , town o f T o b e t s u , r o u t e

No.

32, s o u t h No.

5

( n e a r i n t e r s e c t i o n o f c a n a l ) M l-' h CD C _{L:'ti.:{\ I* 1 . 1 6 6 ~ L L ~ . ~ U l ~ * u . ~ ~ ~ . n m ~ , 3 . b ~ ~ . ~ m} I _{If:l.hlm ~6.0- Rlll.5"} % I I

.

.

F i g .

1 . 4

p. I l l 0 9 rr l; i m l ' - 5 . 4 . I Composition o f r o a d s t r u c t u r e , a . m - o a e e 0

.

I I l l I ! ( i . -. -. -. -. . . - - ? + . - - . . . I I , I i P e a t 1 I I I

i

!

i

f % E l e v a t i o n \-'

-

nGrave1 o Sand =Sandy c l a y -Clay = P e a t mVolcanic a s h

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Ground vrater l . e v e l C 1. aY

_vane

I _{t e s t} P e n e t r a t i o n t e s t Ground w a t e r l e v e l measurcmcnt h o l e --.-Ground w a t e r l e v e l