抄録
Low amplitude repeated loading can cause soil particles to rearrange into a denser and more stable state. When the number of load cycles exceeds the threshold, it results in overstressed soils. This results in accumulation of plastic strains and reduction in shear strength. In some cases, failure planes begin to develop within the soils. Magnitude, duration and the type of loading, all affect strain accumulation and, this needs to be well understood. This paper investigates the effect of multiple loading cycles followed by drainage. This step was repeated a few times before testing the sample up to critical state. In this setup, 100 mm diameter and 200 mm long cylindrical soil samples were arranged on the cyclic triaxial frame. Thousands to a million of sinusoidal loading and unloading cycles were then imposed on the samples. In each case, liquefaction failure was prevented by maintaining low amplitude cyclic stress ratios. In some cases, the samples were allowed to drain in between the cycles e.g. to simulate rail and road embankments. This enabled dissipation of pore pressures from the sample to reach a new state before repeating the cyclic loading. In each case, the rate-of-accumulation of pore pressures and axial-strains reduced with the increase in the number of cycles. The samples were then subjected to undrained shearing at 100 kPa effective stress to investigate the change in strength with the number of load and drainage cycles. The results show that there was a remarkable increase in the stress-strain response of the samples when subjected to recompression. This change was dependent on the number of cycles and cyclic stress amplitude.
