Civil Engineering Reference
In-Depth Information
Gravity loads are generated in the manner described in Chapter 5 (5.7) and applied to the
slope in a single increment. A trial strength reduction factor loop gradually weakens the soil
until the algorithm fails to converge. Each entry of this loop implements a different strength
reduction factor
SRF
. The factored soil strength parameters that go into the elasto-plastic
analysis are obtained from,
φ
f
=
arctan
(
tan
φ/
SRF
)
c
f
=
c/
SRF
(6.39)
Several (usually increasing) values of the
SRF
factor are attempted until the algorithm
fails to converge, at which point SRF is then interpreted as the factor of safety
FS
. For a
detailed description of the algorithm, the reader is referred to Griffiths and Lane (1999)
Subroutines new to this program include
emb
2d geom
and
emb 2d bc
. These sub-
routines generate the mesh and boundary conditions for a standard slope cross-section of
the type shown in Figure 6.15, with dimensions and mesh density controlled through the
units in m and kPa
w
2=20.0
nx2=10
w1=20.0
nx1=20
s1=20.0
2
f
°
c=15
g
=20
h1 = 10.0
ny1=10
1
=20
8-node quadrilaterals
h2 = 5.0
ny2=5
fixed
Element numbering goes from left to right
starting at the top left corner
w1 s1 w2 h1 h2
20.0 20.0 20.0 10.0 5.0
nx1 nx2 ny1 ny2
20 10 10 5
np_types
1
prop(phi,c,psi,gamma,e,v)
20.0 15.0 0.0 20.0 1.0e5 0.3
etype(not needed)
tol limit
0.0001 500
nsrf,(srf(i),i=1,nsrf)
6
1.0 1.2 1.4 1.5 1.55 1.6
Figure 6.15
Mesh and data for Program 6.3 example
