可液化地基土三维地震响应分析

Three dimension earthquake response analysis of liquefaction foundations

编制完全耦合的三维排水有效应力动力反应分析程序,对可液化地基进行三维地震响应分析,探讨了不同土性参数、不同土层构成和不同附加压重等因素对可液化地基抗液化性能的影响。结果表明:在地震荷载作用下,天然饱和砂土地基中的超孔隙水压力随深度的增大而增大;在不同深度处,超孔压峰值到达的时刻比地震加速度峰值到达的时刻要晚;随输入地震加速度的减弱,深层处的超孔压开始消散或基本保持不变,浅层处的超孔压保持不变或略有上升,这一现象与土性参数、输入地震荷载的情况等因素有关;土性参数对土体本身的抗液化性能有重要影响,初始孔隙比越小,相对密度越大,土体的抗液化能力越强;附加压重有利于地基抗液化能力的提高;随着附加压重的增大,超孔压比减小;附加压重对地基中超孔隙水压力的增长有明显的抑制作用。

The fully coupled three-dimension effective-stress dynamic analysis procedure is developed and liquefaction foundations are analyzed. The influence of different soil parameter, different soil layer and different additive pressure on anti-liquefaction nature of the liquefaction foundation is discussed. The research shows that the excess pore water pressure of natural saturated sand foundation increases as depth. In different depth, the arriving time of the peak value of pore pressure is later than that of the peak value of earthquake acceleration. With decreasing of input earthquake acceleration, the excess pore pressure starts to dissipate or keeps constant in deep layer, and it keeps constant or has little rise in shallow layer. This phenomenon is related to soil parameters and earthquake loading etc. The soil parameters have much influence on the anti-liquefaction nature of sands ,for the littler initial void ratio and the bigger relative density , the anti-liquefaction capability of sands is more strong. Additive pressure is useful for improving the anti-liquefaction capability of the foundation; with the additive pressure increasing, the pore pressure ratio decreases. Additive pressure can restrain the effect of excess pore water pressure.