monitoring a criblock retaining wall

7/26/2019 Monitoring a Criblock Retaining Wall

1/27

Report No

CDOH DTP R 90 6

MONITORING

CRIBLOCK

RET INING

Majid Derakhshandeh

Colorado Department of Highways

4201 East Arkansas Avenue

Denver. Colorado

80222

Final

Report

December 199

Prepared in cooperation with

the

U S Department of Transportation

o Federal

Highway

Administration

W LL


2/27

Technical Report

Documentation

Pa

I . A.,o ,'

No.

CDOH-DH-R-90-6

4. Ti,l . o d 5 . Io'i,l.

5.

. , .

c

Monitoring a Criblock Retaining Wall

-

1 q q n

6. P.,Io ,,,,,, O . i

i Cod.

HPR-1567D/74.50

I : ; ~ ~ : ~ ______________________

- 8.

Po,fo,,,,i,.,

O,go i

io Ro,o,r

N

.

I

. A ,horl.)

Majid Derakhshandeh

9.

P. O , ,

O on iu , io N_.

and Add,

Color ado Department

of

Highways

4201 East Arkansas Avenue

CDOH-DH-R-90-6

10. Work U,.i, N (TRAIS)

II.

CO OCI or G,O ' No.

HPR

1567D

-:D:-::e:-n_v:-e_r..;.,_C_O__ ;;0 ;;2; ;;2_2____ _ _ . j 13. Typ.

of

R.port o d

P.,iod C.n, .d

12. Spon i , A,Oftey

N. ,.

oncl Add,

Colorado

Department of

Highways

4201

East

Arkansas Avenue

Denver, co 80222

15. S ppl. ,. ,

.

. N.,

Final Report

Prepared in

cooperation with the U. S.

Department

of Transportat ion,

Federal Highway Administration

16. Ab.troct

Two

cr iblock retaining

walls were

constructed

on

both

ends of a

bridge

on

project BRO

0057(2)

on County Road 17

in Pi tkin

County

in western

Colorado.

This

study was

in i t ia ted

to evaluate the

post-construction

performance of t h i s

propr ie tary

retaining

wall

system. The

walls were

completed

during

March

1989, and

the i r movements were

monitored

through

July 1990.

The

resu l t s of

the

monitoring

program

indicated that

the

wall

movements

were

l imited

to

l ess

than 3/4 of an inch during

the

17 months

monitoring

period, and the walls

appear to be in

satisfactory

working condit ion.

The appearance

of the cr iblock

re ta in ing walls as

well

as

the i r

durabil i ty can make th i s re ta in ing wall system

competit ive with the

other

re ta ining wall

systems

when

applicable.

Implementation

This

repor t

wil l be dis t r ibuted in ternal ly to allow the s taf f bridge

design

group, as

well as

otherbranches in the Highway

Department,

to make the i r own determinations

based on the observations

of th is study.

17. 1C0y

w.

Criblock, Retaining Wall

Monitoring

19. Socurity CI I. lof Ift i . ropo,t)

Unclassified

FDrm DOT ~ O O 7 1-72)

No

Restr ict ions:

This

repor t i s

available to

the public

through the

National Information Service

springfield, Virginia 22161

20. Socu,ity Cluei ' . or 'hie POlO)

21.N Po, 22. P, iu

Unclassified

27

ReprocluctiOft of campletocl pa t . euth.riaocl

i i


3/27

TABLE OF CONTENTS

SECTION TITLE

PAGE NO

I

I n t r o d u c t i o n

1

I I

Background 1

A Mechanics of a concrete cr ib

lock

re ta ining wall 1

B

History of cr ib lock re ta in ing

walls.

I I I

Project locat ion

and

geo logy

4

IV.

Con s t r u c t i o n 7

V.

Monitoring

and

data

ana l y s i s 17

VI.

Con c l u s i o n s 19

Vii

Implementat ion.

21

Bibliography.

4

References

5


4/27

I . INTRODUCTION

The Project

BRO 0057(2)

consisted of a bridge

replacement and

two

re ta in ing

walls

constructed

on

a

county road

in Pi tkin

County,

Colorado

.

This project

was

designed by

a consultant , Integrated

Engineering

Consultants , for Pitkin County.

The consultant proposed and designed the

two

concrete cribwalls ut i l iz ing a criblock system

a t

each end of

the

bridge. This type of

retaining

wall was requested by

Pi tk in

County for

th i s

projec t

due to the fact tha t the

criblock

design would be

more

compatible

with the aesthet ics

of

the project s i t e .

Due

to the proprietary

nature of

the

concrete cr iblock

re ta ining

wall system, and

the requirements

of the FHW

concerning

propr ie tary

retaining walls, t was proposed to

consider

the cr iblock

walls

as

experimental features during

th i s

project . Therefore,

th i s

research

study

was in i t ia ted to monitor the ins ta l la t ion and the long-term

performanmce

of

the cr ib ock retaining

walls for future references.

I I .

B CKGROUND

A. Mechanics of a Concrete Criblock Retaining Wall

A criblock

retaining

wall

i s

basical ly

a gravity-type

re ta ining

structure with

a face

consist ing

of a grid

of precast reinforced

concrete

members,

as shown in Figure 1. The face i s general ly inclined

a t

a slope of

four ver t ica l to one horizontal (unless otherwise

spec i f ied .

Horizontal

members of such a grid

are termed

f ront s t rechers . Where non-standard


5/27

6 ~ r 6'--1

I I

lO L --j r

9.5

0

-r;

FRONT STRECTHER

f

F LSE

HE DER

6 -I r

3'-9'

J c = ~

lO lr-'

3'

-1

c:=::J

f

B CK

STRECHER

10 l.t-

4' -6 I

C ::J

T

4' -6 HE DER

T3

HE DER

1

..,

j t- 2'-7.5

..L_ C]

t CLOSED

F CE

P NEL

Figure l .a

Components of

a criblock retaining wall

......... B CK STRETCHER

Figure l .b Partial structure

of

a cribwall

Figure 1. Il lustration

of

components and formation

of

a cribwa

ll

2


6/27

s t re tcher lengths are required to complete the end of

a

wall ,

they

are

termed closers . The face

members

are connected

by

t ransverse

members

termed headers to a

simi lar

grid

of back

s tre tchers paral le l to the face

and

located

so

tha t

the

overal l

thickness

of the

wall

is

not

less

than

three

fee t . o

complete

the wall,

some

addit ional spacers, termed fa lse headers,

may also be

used

i f the system

requires

i t . Headers are to be

perpendicular

to

the

face

of

the wall .

B

History of

Criblock Retaining Walls

The

cr iblock

re ta ining s t ructures were introduced to the United s ta tes

over a

decade ago. Europe has

played a

bigger ro le

in developing th i s

technology,

but

the f i r s t documented

case his tory goes back to

1966

1

in

Austral ia .

The

l i t e r a tu re obtained on th i s case his tory indicated t ha t the

f i r s t wall was bui l t

in Aust ral ia

and i t consisted

of concrete

panels

to

complete the wall.

During the

past two

decades, the criblock idea has been used to

bui ld

various re ta ining s t ructures ut i l iz ing various elements such as concrete

panels, t reated

wood

members, or used t i res . The American

Wood Preservers

Ins t i tu te reports

of

another project

2

which consisted

of

building

a 22

foot

high

re ta ining

s tructure

with

t reated wood members

bol ted together and

f i l l ed

with

rock

or other

sui table

material .

The

Ins t i tu te

of

Civi l

Engineers also reports

of

a case his t

ory

3 where used t i r e s

were

used to

bui ld

a

cr ib wall 40

M long

and

3.7 M high

to

form a

f l a t parking area.

The unusual const ruct ion deta i l of the wall concerns the

use

of

some

4,000

used

t i r e s ,

which

were

l a id by f ive

men

and two mechanics a t

a

ra te

of

up to

3


7/27

360 t i res

per

8

hour day. Firs t

a

layer of

t i res was

placed to give

maximum

in ter lock with the previous layer,

using l ink bars where

necessary.

Then,

a crawler

loader

placed

shale and s i l t s tone

f i l l over the t i r e s and

workers

shovelled

the

f i l l

in to the

t i res .

Finally,

a Bomag vibrat ing

ro l ler

compacted

and leveled the

f i l l .

The

sequence

was

then

repeated

for

each

layer of

t i res .

The

use

of cr iblock

retaining

walls

using

concrete

panels

has become

more popular, and

t

has

found

many

commercial

applications.

Some

of these

commercial applications

include:

a.

Highway

Applications

b. Slot-cut Walls

c. Sound Barrier

d.

Multiple Depth

construct ion/and

e.

Landscaping.

I I I . PROJECT LOC TION ND

GEOLOGY

The Project

BRO 0057 2)

was located on

county

Road

17, in Pi tk in

County, as

shown

in Figure 2. Construction during

th i s project

consisted o f

replacing the Gerbiz bridge across the Roaring

Fork

River, northwest

of

Woody

Creek.

The

new

bridge replaced

the

old bridge about

20

fee t

upstream, as

shown in Figure

3.

Chen

and Associates

was

selected to perform the geological

study

of

the s i t e

and

make

recommendations

on

the types of

foundations appropriate


8/27

STATE DEPARTMENT OF HI

GHWAYS

DIVISION OF HIGHWAYS STATE OF COLORADO

PLAN AND PROFILE OF PROPOSED

FEDERAL

AID PROJECT NO BROQO?1 1)

COUNTY RO D

NO.\l

PITKIN COUNTY

I tAc.n , Cltog

11 1 20

MGII .

::::

I: = : ~

UfIIC _ . . . . .

.

8JIOwIt

AI GAoI IW., . . . . . . .

'1111

STA o.QO

igure

2. geological location

of

project BRO 0057(2)

5


9/27

OUNTY

RO D

16

PROPOSE ) \

\

l OF NEW

BRIDGE \

FLOW

/

RO RING

FORK

RIVER

.

\

' \

( = 20

\

Figure 3

Skematic of the location of the new bridge

relative to the old one

6


10/27

for th i s project .

The

resu l ts

of the geological study indicated that the subsurface

condit ions

encountered

a t

the

s i t e

consisted

of

a

variable

depth

of

man

placed

f i l l

overlying natural gravels

and cobbles at

the east

abutment

boring and

sandstone bedrock a t the west abutment boring. Ground

water

was

encountered a t

the

r iver elevat ion in

the boring near

the east

abutment.

Based on the laboratory tes t ings and the f ie ld

observations, t

was

recommended to use spread footing foundations for both abutments to support

the

bridge

s tructure . I t was

also calculated

that the spread

footings

may

undergo a to ta l

settlement

of one inch or less which was

categorized

as

being

acceptable.

Based

on the

above f ie ld

investigation

and

the

request of the

county,

t

was decided to

bui ld

two cr iblock re ta ining

walls

to

re ta in

the

so i l

on

both

ends

of

the bridge

and provide an aesthetically desirable look for the

environment.

IV. ONSTRU TION

For th i s project the two cr iblock re ta ining

walls

were designed by

re ten t ion

engineering

and

they

were

constructed using

the pre-cast

reinforced concrete cr ib members as shown in

Figure

4.

The wall on the east end of the r iver was

designed

to be 9 feet long

and 10

feet high. The

segment

on

the west end of

the r iver was much smaller


11/27

component Detai ls

D I E ~ I O ~ l in I

UNIT

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:III

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.

eo

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1- - - - - - - -

.

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I

S7 .

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120

PILLa

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~ I - - - - - - - - - - - - - I

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-

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1111

:s :z

So

'1

82

142

.

84

1:110

7 .

Figure

4. details

of the

pre-cast

reinforced concrete

crib

members

8


12/27

in

length,

but

was

designed

to be a few feet higher compared to the

one

on

the

opposite side.

Figure 5 shows the detai ls of the cribwa11s for th i s

project .

The

construction

of a cribwa11

i s

basical ly

an

easy

process.

The

originators

of cribwa1ls would l ike

to

think of

th i s

process as a one man

one

block

operat ion. The most

important

c r i t e r i a

to

consider is the

preparat ion of

the cribwa1l

base. o

special

concrete

slabs

are required,

but

the base

needs to be cleaned and

perfect ly

leveled

to

the required

grade

so that the f i r s t

cribwall

components are placed

on

the

top

of

a uniform

and

firm base providing

an

adequate

foundation

for

the re s t

of

the wall.

To

begin the wall

construction,

an appropriate amount of

excavation

was performed

on

both

ends

of

the bridge for

placement

of

the

crib10ck

components. Excavation on the west

end of

the r iver was carried

out

with

an

extreme

amount of di f f icu l ty due to the

presence

of

sandstone

near

th is

end

of the bridge.

The

base of the

walls was

cleaned

and compacted using

vibratory hand

compactors as

shown

in

Figure

6. Addit ional soi l gravel, or

a

mixture was

placed and compacted to

create the

four ver t ica l to one

horizontal

slope a t

the

wall base. During

t h i s project , four to f ive inches of sandy

gravel

was

used as base

material

at

the

bottom

of

the

walls

due

to

the

high

ground

water elevat ion encountered

a t

the r iver level . Figure 7 shows the

s ~ d y

gravel

blanket prior

to

construction of

the walls.

Once the

base

preparat ion was

completed, the r es t

of

the

wall was

9


13/27

LlyATION

..

.ll.A.IL

i i .

J

~ : 1 :

u ~ .

t t

. REVATION t

Figure

5.

a

DRAWINGS

NOT TO

SCALE

_

......

--r

~

' - ~ ' : ....

......

.

I . ~ r _

-

T :=.= ....

r ..... - '

. .

. u ~

~

...............- .... .......

..

: .:::.

: ::.

:.=.::.:.. :::=

== = 1

~ ~

.......................

-

_...... ..

_ M I _

UIYD

Details of the cribwa l ls in project RO 0057(2)

10


14/27

Figure 6

Figure 7

'.,

.I

.

J

',.

..

.

. 1

.

./

oundation preparation for the e st wall

Placement of granular

soil

t the base of the

wall

11


15/27

erected

without

much

di f f icu l ty

The

cribwall

members

were handled

by the

laborers

present

a t

the s i t e by simply stacking

them

on top

of

one

another

and

making

sure the

alignment

and the required

grade

were preserved.

The f i r s t

course of cribwall

units was the

f ront

and

back s tre tchers

or

closers) . This step

was careful ly

done

to

ensure firm bedding against

the

base

so i l s

Figure

shows the placement of front and back s tre tchers

at

the

east end

of the

large

cribwall .

The cribwall

cel ls

were placed

in

horizontal l i f t s

and

they were

backfi l led af ter placement

of

maximum three l i f t s The backf i l l so i l s

consisted

of granular soi ls with

a large

percentage of gravel and free from

organic

material .

The

backfi l l ing

was accomplished by a f ront loader

slowly

pouring

the backf i l l

so i l in to

the completed cr ibwal l ce l l s

The next

s tep was

to compact the backf il l so i l

contained

in

the

ce l l s

This

was done

by

using a special hand-held vibrator small enough

to

be

placed inside

the

cel ls

and

provide

85 percent or higher

of

AASHTO

T-99

compaction

a t

optimum moisture

content .

The compaction

ef for t was performed

for each

foot of

backf i l l so i l which was poured

in to

the

cribwall cel ls

Figures 9

to

16 show the progress of the cribwall construction on

the east

end of the r iver

The construction of the cribwalls

followed

a simple

procedure

and

required no

heavy

equipment for completion of the walls . The cr ib members

consis ted of

precast ,

reinforced concrete elements

l igh t

enough

to be

handled by one man The

base

of the walls required no special treatment

2


16/27

Figure 8.

Figure 9.

. .

.

: : ' .

' ...

11+

,

monitoring a criblock retaining wall

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