ABSTRACT
Behavior of sand during secondary liquefaction, liquefaction caused by propagation of excess porewater from the liquefied layer, is investigated. Six Toyoura sand specimens with 50% relative density are tested. Two of them are loaded monotonically under the initial confining stress σ’ c =100 kPa and 0 kPa, respectively. The rest are loaded cyclically up to excess porewater ratio becomes 20, 40, 60, and 100kPa starting with 100kPa initial confining stress at first. Then the confining pressure is set zero by increasing the back pressure, and loaded monotonically. Stress-strain curves can be classified into three groups; that of monotonic loading with σ’ c =100kPa, that of initially liquefied case, and those with secondary liquefied cases. This indicates that behavior of soil during secondary liquefaction can be represented by the monotonically loaded case with σ’ c =0kPa unless soil structure is disturbed during cyclic loading. Disturbance of soil skeleton occurs when cyclic mobility behavior appears.
