CEEN 341 - Lecture 15 - Elastic Settlement and Primary Consolidation Settlement

This lecture introduces the idea of predicting elastic (or immediate) settlements in coarse-grained soil, and primary consolidation settlements in fine-grained soils. The governing mechanisms that contribute to each type of settlement is introduced and discussed. The Standard Penetration Test (SPT) is briefly introduced and explained. Consolidation tests are introduced, and the various components of a consolidation curve are explained. Definitions are provided for overconsolidated soil, normally consolidated soil, and overconsolidation ratio. Some reasons for why soil becomes overconsolidated are given. The graphical method to estimate the preconsolidation pressure is demonstrated and explained. A method to perform a field correction to consolidation curves is presented.

Critical Questions to Consider:
1) What is the difference between immediate settlement and primary consolidation settlement?

2) Why does it take so long for primary consolidation settlement to occur sometimes? Which factors affect how long it will take for the settlement to occur?

3) Why is it important to minimize disturbance to soil samples that are going to undergo consolidation testing? Why would it be important to obtain an accurate estimate of the preconsolidation stress?