Home
Introduction
Theoretical_Background
Method of Slices
Bishop
Spencer
Morgenstern & Price
Use of Limit Equilibrium
Choice of Geometry
Strengths & Pressures
Long Term Problems
Short Term Problems
Summary
References
Input Instructions
Geometry
Boundary Forces
Pore Pressures
Strength Parameters
Earthquake Loading
Iteration Control
M-P Method
Convergence
Examples
Example 1
Example 2
Example 3i
Example 3ii
Example 4
Previous
|
Next
|
Strength parameters for TSLOPE are specified at the base of each slice. This allows the user to base his choice of strength parameters on soil type, stress conditions, direction of slip surface or other factors. The user may specify a curved Mohr-Coulomb strength envelope if desired. The relationship between shear strength and normal stress becomes:
 |
(20) |
s = shear strength
c = cohesion
= normal stress on base of slice
1 = friction angle at atmospheric pressure
= reduction in friction angle per 10-fold increase in
Pa = atmospheric pressure
A straight failure envelope may be specified by simply setting = 0.
For effective stress analyses, the parameters c', ', and ' should be specified in order that the shear strength be computed as a function of the effective normal stress at the base of the slice.
For undrained analyses, the friction angle will normally be set equal to zero and the cohesion term will be set equal to the undrained shear strength, the undrained shear strength being determined as a function of the consolidation stress conditions, the direction of the slip surface and so on. However, the undrained shear strengths can also be computed as a function of the normal stresses at the base of each slice by using the parameters c, and to define a total stress strength envelope or to define the relationship between 
ff and 
fc that is established by laboratory tests (see Johnson, 1974, for a discussion of the difference between these two ways of describing the variation of undrained strength with confining pressure).
TSLOPE allows the undrained shear strength to be determined automatically as a function of the vertical effective stress. An Su/'vc ratio is entered in which Su is the undrained shear strength and 'vc is the vertical effective stress at the base of the slice.
The program calculates 'vc and multiplies by Su/'vc to determine Su.
Combined S-R strength envelopes can be prescribed by using the option to specify a second set of values for c and , the second set being the drained values. The primary set of values of c, and should be used to specify the undrained strength envelope as this is more likely to be curved. In any event, the program chooses the lower set of strength parameters for the normal force on the base of that slice.
Top of Page
|
Previous
|
Next
|