Geotechnical Design: Simulation of a Real-World Scenario

Geotechnical design 1
GEOTECHNICAL DESIGN
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Geotechnical design 2
Introduction
The case study is about simulation of a geotechnical scenario of the real world. This
simulation is stress-deformation case. With the help of basic knowledge of soil mechanic, finite
element analysis (FEA) and numerical analysis, to perform the simulation. The effect of
surcharge and preference of water table is considered during the analysis.
The insitu site conditions are soft clay and below it is plastic marl. The water table is 6m
below the ground surface. On the first day of construction, involves stabilization of the soil by
added a granular fill and compacted to a depth of 1m (Barnes, 2016). On the next day, it involves
the construction of foundation which is made of flexible steel. Then on day three, assembly of
the water tank is done. After the assembly, water is filled uniformly for 7 days to 70% of the
tank.
The software specified for the analysis is GeoStudio. The help of finite element and
numerical analyses is used to perform the analysis. The study problem is a stress deformation
situation, then the SIGMA/W is preferred feature for a stress deformation of an earth structure.
Problem statement
The problem involves applying circumferential stress by a cylindrical tank to a soil which
is symmetrical about a vertical axis. This is a three-dimensional case, therefore due to line of
symmetry at the centre of the circle it can be analyzed as a two-dimension.
Objectives
 To visualize the settlement of the soil
 To determine the changes in vertical stresses

Geotechnical design 3
 To determine the excess pore water pressure on both short-term and long-term basis
Literature review
The analysis of stress-deformation is performed in consideration of the water table effects
and surcharge on a multi-layered soil. The basics of soil mechanics is key to perform this
analysis.
Elastic analysis
In elastic analysis the assumption is that the soil is isotropic linear elastic material. The
stress uses the linear stress-strain relationship due to the applied load (Chehade & Shahrour,
2008). To obtain stresses at a particular area needs integration from the point solutions loads.
The vertical displacement under the area carrying, a uniform pressure on the surface of soil with
linear stress-strain relationship can be express as
si= qB
E ( 1−v2 ) I s
Where
siis vertical displacement
I s is the influence factor depending on the shape of loaded area
B is width or diameter
E is modulus
v is poisson’s ratio
q is applied force

Geotechnical design 4
Non-linear elastic analysis
The soil considered is not isotropic
The total vertical stress(σ v)
With the knowledge of stress being force acting on an area. For soils, the weight acting at
point below the ground surface due to everything above it (Indraratna, et al., 2015). Its
parameters are the density of soil and the depth. Any change of vertical stress(∆ σv ), can result in
the horizontal stress (∆ σh )at the same point. This does not mean that the change in vertical stress
is equal to change in horizontal stress.
σ v=γz
Pore-water pressure (u)
It is the pressure of the void space due to the presences of water. It is affected by the
seepage flow conditions. It is express as
u=γ w z
Effective stress (σ ')
It is the stress transmitted on the soil skeleton only.it is also the difference between the
total stress and the pore-water pressure.
σ '=γz−γ w z