Soil mechanics--Triaxial test

wkh023002

1. The problem statement, all variables and given/known data

Generally, the triaxial tests can be classified as three types, i.e., UU, CU, and CD tests. The type of test to be adopted depends on how best we can simulate the field conditions. In other words, the purpose of carrying out a particular test is to simulate field conditions as far as possible. For example, because of the high permeability of sand, consolidation occurs relatively rapidly and is usually completed during the application of the load. Shear strength parameters from CD tests are therefore generally used in design. Consider the following two cases:
a) In what situations, results from CD tests for a clay soil can be used in design.
b) A earth dam is to be constructed. The soil on the site is clay. The initial water level is at the ground surface. During the construction, the water level has to be lowered in a short time, so that construction can proceed. This condition is commonly known as “sudden drawdown”. What type of triaxial tests would you recommend to carry out, and why?


2. Relevant equations



3. The attempt at a solution
I dont know why Consolidated Drained test can be used to test clay. Clay is impermeable and drainage can take very long time to complete. Any situation would allow this happen?

As for b), i think CD test should be used. Since it drainage allows fast drawdown.
but im not sure if it is correct.

Actually, I am poor at soil mechanics. I would like to seek your help on this question
I am always confused with the abstract concepts!
Thanks!