Earthwork: Vincent Chu Answers

In determining the effective stress parameters of a soil sample, which test is preferable, consolidated undrained test or consolidated drained test?

The effective stress parameters of a soil sample can be obtained from both consolidated undrained test and consolidated drained test.

However, consolidated undrained test is normally selected because of the following reasons:

(i) Time taken for consolidated undrained test is lesser than that of consolidated drained test.

It is because consolidated drained test requires the full dissipation of excess pore water pressure of the soil during testing and it takes long time when soils of low permeability are tested.

(ii) Useful information can be obtained from the stress path of consolidated undrained test.

(iii) Failure occurs in lower stress level when compared with consolidated drained test.