Soil Behaviour and Geotechnical Modelling 8

Authors Avatar

CSE-538 Soil Behaviour and Geotechnical Modelling

Assignments 8

Treds Chan

1050285G

10Dec 2010

 

Assignment 8 (Lecture 8 – 1-D elastic visco-plastic models):

8.1

(a) Explain why clays or clayey soils can creep (the mechanisms).  

Creep is the gradual deformation or displacement occurring in response to an applied stress. It is due to viscous adsorbed water (double layers) on clay particles; viscous deformation of clay plate; and viscous re-arrangement/sliding/deformation of the group of clay plates that called skeleton, like frames. (Figure 8.1)

Figure 8.1 Mechanisms of absorbed water and creep of clays or clayey soils

(b) What are the definitions of creep, relaxation, strain rate effects and time effects?

Creep: Creep is the gradual deformation or displacement occurring in response to an applied stress. Soil gets into the creep stage after its primary consolidation. In the stage the effective stress is invariable, whereas the deformation still grows at a low rate with time.

Join now!

Relaxation: Stress relaxation describes how materials relieve stress under constant strain. Its  nonlinearity is described by both stress relaxation and creep.

Strain rate effects: When creep happen under the undrained normal-consolidation condition and drained over-consolidation condition, the creep strength decreases along with the

decreasing of the strain rate.

Time effect: When creep happens under the undrained normal-consolidation condition and drained over-consolidation condition, the creep strength Su decreases with the extending of loaded time.

(c) Explain the concept of “equivalent time” for creep.    

“Equivalent time” for creep is the time of creep down from the reference time line ...

This is a preview of the whole essay