Introduction to Modeling
Tuesday, August 21, 2012
12:43 PM
Numerical Techniques Covered in this Course
Finite Difference Method (FDM)
Finite Element Method (FEM) (Introduction)
Commercially Available Software Packages
FLAC (Fast Lagrangian Analysis of Continua) (General FDM)
ABAQUS (FEM) (General FEM with some geotechnical relations)
ANSYS (FEM) (Mechanical/Structural)
PLAXIS (FEM) (Geotechnical)
SIGMA/W (FEM) (Geotechnical)
SEEP/W (FEM) (Seepage Analysis)
MODFLOW (FEM) (Groundwater Modeling)
FLAC and PLAXIS are the most commonly used by advanced
geotechnical consultants
Common Applications of Modeling in Geotechnical Engineering
Numerical approximation for various types of differential
equations commonly encountered in geotechnical engineering
LaPlace's Equation (governing equation for 3D steady-state
flow)
Steven F. Bartlett, 2010
L1 - Intro Page 1
Common Applications (continued)
Tuesday, August 21, 2012
8:41 AM
Groundwater Flow Equation (3D transient flow)
= k/Ss = hydraulic conductivity / Specific Storage
G = source/sink term
Equation of motion for forced damped vibration system
The behavior of the spring mass damper model when we add a
harmonic force takes the form below. A force of this type could,
for example, be generated by a rotating imbalance.
If we again sum the forces on the mass we get the following
ordinary differential equation:
See next page for solution for homogeneous material; however
heterogeneous materials require numerical methods.
Steven F. Bartlett, 2010
L1 - Intro Page 2
Common Applications (continued)
Thursday, March 11, 2010
11:43 AM
Wave equation for solid materials
The wave equation is an important second-order linear partial
differential equation of waves, such as sound waves, light waves
and water waves. It arises in fields such as acoustics,
electromagnetics, and fluid dynamics (from Wikipedia).
Steven F. Bartlett, 2010
L1 - Intro Page 3
Common Applications (continued)
Thursday, March 11, 2010
11:43 AM
Deformation Analysis of Slopes
In deformation analysis we seek to estimate how much the
slope will move or deform. This is much more of an involved
process than simply calculating the factor of safety against
failure from pseudo-static techniques.
Deformation Analysis of Tunnels
Steven F. Bartlett, 2010
L1 - Intro Page 4
Common Applications (continued)
Thursday, March 11, 2010
11:43 AM
Dynamic Analyses
Rocking analysis of a geofoam embankment undergoing earthquake
excitation.
Steven F. Bartlett, 2010
L1 - Intro Page 5
Reading
Tuesday, August 21, 2012
12:43 PM
FLAC v. 5.0 User's Guide, Section 1: Introduction
FLAC v. 5.0 User's Guide, Section 2 (p. 2-1 to 2-12)
Applied Soil Mechanics, Ch. 1 Properties of Soils
Steven F. Bartlett, 2010
L1 - Intro Page 6
Assignment 1
Tuesday, August 21, 2012
12:43 PM
Assigned Reading
Install FLAC v 5.0 software on your computer
Run the following code to check the model (see FLAC manual
Example 4.8 Slip in a bin-flow problem)
config
grid 7 10
model mohr i=1,5
model elastic i=7
gen 0,0 0,5 5,5 3,0 i=1,6 j=1,6
gen 3,0 5,5 6,5 6,0 i=7,8 j=1,6
gen 5,5 5,10 6,10 6,5 i=7,8 j=6,11
fix x y i=7,8
fix x i=1
prop dens=2000 shear=1e8 bulk=2e8 fric=30 i=1,5
prop dens=2000 shear=1e8 bulk=2e8 i=7
int 1 Aside from 6,1 to 6,11 Bside from 7,1 to 7,11
int 1 ks=2e9 kn=2e9 fric=15
set large, grav=10
step 3000
ret
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Thursday, March 11, 2010
11:43 AM
Steven F. Bartlett, 2010
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