Investigation of K(o) Testing in Cohesionless Soils

The ratio of horizontal to vertical effective stress when lateral yielding is prevented is known as the coefficient of earth pressure at rest and is denoted by the symbol Ko. Ko values and the stress-strain response of soils under conditions of lateral restraint are important engineering quantities for problems involving settlement of large fills, lateral pressures on retaining structures, and yielding around excavations. In this report, four laboratory techniques and devices for experimentally determining Ko values and the stress-strain relationships of Reid-Bedford sand are examined. These methods are the linear variable displacement transducer LVDT clamp, the Ko belt, swinging arms lateral strain sensors, and an indirect volume change method using a burette. The tests were conducted at three relative densities, 25, 75, and 100 percent, using modified triaxial compression chambers.