TABLE OF CONTENTS As the name implies, the undrained shear strength s u refers to a shear condition where water does not enter or leave the cohesive soil during the shearing process.
In essence, the water content of the soil must remain constant during the shearing process. There are many projects where the undrained shear strength is used in the design analysis. In general, these field situations must involve loading or unloading of the cohesive soil at a rate that is much faster than the shear-induced pore water pressures can dissipate.
During rapid loading of saturated cohesive soils, the shear-induced pore water pressures can only dissipate by the flow of water into (negative shear-induced pore water pressures) or out of (positive shear-induced pore water pressures) the soil. But as will be discussed in Chap. 12, cohesive soil has a low permeability, and if the load is applied quickly enough, there will not be enough time for water to enter or leave the cohesive soil. For such a quick loading condition of a saturated cohesive soil, the undrained shear strength s u should be used in the analysis.
The unconfined compression test is a very simple type of test that consists of applying a vertical compressive pressure to a cylinder of laterally unconfined cohesive soil. The unconfined compression test is also known as a simple compression test.
The unconfined compression test is most frequently performed on cohesive soils that...
