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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
7/26/2019 Monitoring a Criblock Retaining Wall
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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
7/26/2019 Monitoring a Criblock Retaining Wall
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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
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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
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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
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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
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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
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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
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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
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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
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component Detai ls
D I E ~ I O ~ l in I
UNIT
z
:Z0
- :II
H
":II
:III
.
4
'.
.
eo
PH
ITMTCKK /
C L a n
t
A
I
C
4.'
Sea
eo
1- - - - - - - -
.
- - -
I
S7 .
1'.
,.
120
PILLa
I A I
~ I - - - - - - - - - - - - - I
P
u\
2 . .:. .,_1 roinforca_nc I . ha . . 1 :1 In. mlnln ...
n
_ r
:; :1,2 0
mIni .......
It =40 ,000 , I f t . ,
.m
.
"
C
D
0
0
7
14
2
1
22
22
:M
-
41
WT
1111
:s :z
So
'1
82
142
.
84
1:110
7 .
Figure
4. details
of the
pre-cast
reinforced concrete
crib
members
8
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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
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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
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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
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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
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Figure 8.
Figure 9.
. .
.
: : ' .
' ...
11+
,