Stress-strain behaviour of granular soils under monotonic and cyclic loading conditions
The stress-strain behaviour of granular soils under monotonic and cyclic loading conditions and small lateral strains was studied in this work. A simple cubic triaxial apparatus (SCTA), originally developed at Leeds University for monotonic stress-strain studies of sand under controlled and small lateral strains, was used in this investigation. The three principal stresses and strains can be independentLy controlled and measured in this apparatus. The SCTA was modified and further developed to allow cyclic stress-strain studies of granular soils-to be performed. To increase the stress-strain data available on granular soils similar tests to those previously carried out on the medium sand, were performed on fine and coarse sands under monotonic loading conditions. The samples tested were cubic of 150 mm side length and prepared with ranges of initial porosities in a dry condition. To study the cyclic stress-strain behaviour of sand at small strains, a series of new tests on similar cubic samples of the medium sand were performed under cyclic loading conditions. Cyclic loads with different frequencies, amplitudes and number of cycles were applied and the samples were prepared dry at the loosest and densest conditions. Values of the coefficients of active pressure, earth pressure at rest, constrained secant modulus, Young's modulus and Poisson's ratio for the fine, medium and coarse sands were obtained and compared for different conditions. The relationships between vertical and lateral stresses are found and the volume change behaviour of sands in different conditions are studied. Finally some comparisons are made between the results obtained from monotonic and cyclic loading conditions.