671017.pdf

Table 1: Summary of material parameters.

Initial conditions Elastic properties Shear strength Hydraulic properties

CDG fill soil

훾푑= 1.41kg/m^3 ,

푒 0 = 0.86,

푀푐0= 14.9%

휇 = 0.05

휅 = 0.011

푐耠=2kPa,

휙耠=32∘

휓=5∘

k-Figure 4

SWCC-Figure 4

Soil nails — 퐸 = 2.5 × 10

(^4) MPa,
휇 = 0.2 ——
In situ ground — 퐸=35MPa,휇 = 0.25 ——
No-fines concrete — 퐸=1×10
(^4) MPa,
휇 = 0.2 — 푘 = 1.0 × 10
−4m/s
Soil-nail interface — 퐸=10휇 = 0.2MPa, 푐
耠= 10.6kPa,
휙耠= 35.8∘ —
E,휇,휅,푀푐0,훾푑,e 0 ,k,푐耠,and휙耠are Young’s modulus, Poisson’s ratio, the slope of the unloading-reloading line on the]−ln푝耠diagram, initial moisture content,
dry density, initial void ratio, permeability coefficient, cohesion intercept, and internal friction angle, respectively, and the subscript “0” denotes the initial value.
0
10
20
30
40
50
60
70
80
1 3 5 7 9 11 13 15 17 19
Surcharge
pressure
(kPa)
Day
Stage 2
Stage 3
Stage 4
Stage 1
Figure 2: The applied surcharge process during the field test.
allows only one half of the slope to be modeled. The finite
element mesh is set up according to the actual geometry of the
slope and the soil nails. As shown inFigure 3,theslopefills
and the ground soil are modeled using a finite element mesh
consisting of 114815 8-node linear solid elements. Each node
has four degrees of freedom, one for pore water pressure and
three for displacements. Since a layer of asphalt was applied
above the natural ground surface as a watertight measure in
thefieldtest,itisassumedinthisstudythatredistributionof
water content is negligible within the in situ ground. Hence
only displacements are taken as the field variables for the
ground soil in the model. The drainage layer (i.e., no-fines
concrete layer) is also simulated as a deformable porous
medium by solid finite elements with coupled nodal variables.
Regarding the soil nails, each steel bar and surrounding grout
are idealized as a cylindrical bar of the same diameter and are
represented by solid elements with only displacement vari-
ables (see the inset ofFigure 3).
The displacement boundary conditions of the numerical
model are taken as vertical rollers on the left cutting edge and
therightsideofthetestslopeandfullfixityatthebaseandthe
constrained region at the concrete apron near the toe. Since
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Soil elem ent
Interface elem ent
Nail elem ent
Slope lls
No-nes
concrete
In-situ soil
Z
Y
X
Figure 3: Finite element model of the nailed test slope (the inset
figure shows the detailed modeling of soil-nail interaction).
no water could flow out from the unsaturated slope during the
surcharge process, no-flow conditions are assumed along the
outer boundary of the entire model. Moreover, the interfaces
between the no-fines concrete layer and the surrounding soils
areassumedtobecontinuouswithnoslippageallowedasa
deep-seated failure mechanism along the interfaces was not
observed in the field test.
The average void ratio and degree of saturation of the soil
measured prior to the field test have been adopted as the ini-
tial conditions for the analyses (Ta b l e 1). The initial distribu-
tions of internal stresses and pore water pressures within the
slope under the gravity loads are then obtained by initial equi-
librium calculations before surcharge loading is imposed on
the slope. The surcharge is simplified as a uniformly distrib-
uted pressure applied to the crest of the slope, as prescribed
by the covering area of the concrete blocks during the field
test.
3.3. Soil Models and Parameters.As in previous plane strain
study [ 13 ], the fill soils are modeled by the Mohr-Coulomb
plasticity model with a nonassociated flow rule. To represent
the stress-dependent stiffness property of typical residual