Shear strength

To appreciate the ways in which stresses and strains in soils can be represented. To understand the mechanisms that can produce failure in soils including the effects of pore water pressures and drainage conditions. To appreciate the factors affecting the shear strength of sands and clays and the test procedures adopted. To introduce the theory of critical state soil mechanics. In soils failure occurs as a result of mobilising the maximum shear stress the soil can sustain, therefore an understanding of shear strength is fundamental to the behaviour of a soil mass. The shear strength of the soil, allied with a particular method of analysis, will determine the maximum or ultimate (failure) load. In limit state design the shear strength of the soil is used to determine the resistance to failure such as in foundation loading or slope instability. By using characteristic values of strength and applying partial factors to these strengths a design value of resistance is obtained, usually from a calculation method.