TABLE OF CONTENTS As indicated in Table 5.2, soil can be classified as being either nonplastic or plastic (ISBP soil classification system). The shear strength of nonplastic soils, also known as cohesionless soils or granular soils, has been discussed in Chap. 8. Typical types of cohesionless soils are sands and gravels.
This chapter deals with the shear strength of plastic soils, also known as cohesive soils. Cohesive soils have fines, which are silt and clay size particles that give the soil a plasticity or ability to be molded and rolled. As indicated in Table 5.2, typical types of cohesive soils are silts and clays. The shear strength of cohesive soil is much more complicated than the shear strength of cohesionless soils. Also, in general the shear strengths of cohesive soils tend to be lower than the shear strengths of cohesionless soils. As a result, more shear-induced failures occur in cohesive soils, such as clays, than in cohesionless soils.
The shear strength of cohesive soil can generally be divided into three broad groups:
Undrained shear strength (Secs. 9.3 and 9.4). This is also known as the shear strength based on a total stress analysis.
The purpose of these laboratory tests is to obtain either the undrained shear strength s u of the soil or the failure envelope in terms of total stresses (total cohesion c and total friction angle ?). These types of shear strength tests are often referred to as undrained shear strength tests because...
