Microsoft Word - Chap.4 Lateral Earth Pressure and Retaining Wall 01 for student _p.160~171_.doc160
1) General
Influence factors
1)
2)
3)
depending on wall movements (or deformation modes of soil elements).
2) Lateral Earth Pressure


''
Brooker and Ireland,
161
h'
h
0
OCR))(sin-(1
OCR)(
φ=
or
'sin'
For dense sands,
Geotechnical Engineering
162
* Rankine Approach
* Coulomb Approach
a) Rankine
Wall movement for active state Failure plane for active state
Wall movement for passive state
Failure plane for passive state
γ, Ko (<1)
163
(Active state) (Passive state)
PA = γ'ztan 2(45-φ’/2) - 2c’tan(45-φ’/2)
= γ'zKa - 2c aK
PP = γ'ztan 2(45+φ’/2) + 2c’tan(45+φ’/2)
= γ'zKp + 2c pK
164
(1) φ’, c=0
Pw =γwz = z → Water pressure,
PA << Pw → Water loads are very important.
(2) c, φ=0
H
Z
H/3
EA
R
165
backfill
Based on assumption that the resultant force, EA R, is parallel to slope of
backfill, Rankine’s active pressure and resultant force can be obtained as
below
R
R
where
φββ
166
C
AE is a function of (a) geometry of wedge (H, β, ω, θ)
and (b) soil properties (c, φ’, δ, cα,γ)
Known : a)
failure surface
shear force (friction only)
167
(i) Assume θ
(ii) Calculate C
WWWW
RRRR
168
AE (θ) and pick max. value.
This max. value is active earth pressure resultant.
* Analytical Solution for Coulomb’s Method (c=0, φ φ φ φ soils)
Active earth pressure resultant
+ω+δω
ω−φ =
−ω−δω
ω+φ =
169
(1)
(2)
(3)
tan
r0
r
α
170
3) Movements to mobilize limit state (i.e. active or passive failure state)
US army corps No.4, Fig 3-2.
Relationship of Earth Pressures to Wall Movements
(after Department of the Navy 1982)
Geotechnical Engineering
171
DM7 USAC Das Coduto
Dense Cohesionless
Loose Cohesionless
Stiff Cohesive
Soft Cohesive
Movements