Post-cyclic loading settlement of saturated clean sand

Saturated sand deposits may experience significant settlement or reconsolidation with the dissipation of excess pore pressure in the post-cyclic loading phase even if liquefaction has not occurred. This paper presents results from an extensive and systematic experimental study on the factors governing the post-cyclic loading settlement of saturated clean sand. Strain-controlled, undrained, triaxial tests were performed on reconstituted specimens of Ottawa (C-109) sand. Effects of excess pore pressure, induced shear strain, consolidation stress, number of loading cycles, and relative density on post-loading settlement were investigated. It was found that the settlement potential during the post-loading phase is strongly correlated to the excess pore pressure; the larger the excess pore pressure the greater the settlement. The potential to develop excess pore pressure, however, decreases considerably with increasing consolidation effective stress in the range between 100 kPa and 400 kPa. Additionally, the level of induced shear strain and the number of loading cycles were confirmed to be important factors in the development of excess pore pressure and post-loading settlement. The results revealed a unique relationship between initial liquefaction and post-loading settlement. Specimens that were loaded up to initial liquefaction were found to experience about the same volumetric strain in the post-loading phase, irrespective of the induced shear strain.