珊瑚礁砂与标准砂场地液化特征动力离心试验研究

Dynamic centrifuge model test study on liquefaction characteristics of coral sand and standard sand

珊瑚礁砂场地液化特性与抗液化处理措施是热带港口建设的关键问题之一。基于动力离心模型平行试验,从超静孔压、场地放大效应、地表沉降及反演分析剪切模量和阻尼比等方面,对比珊瑚礁砂和标准砂自由场地的地震液化特征。结果表明:相同条件下,珊瑚礁砂场地触发液化的荷载强度要显著高于标准砂场地,而液化深度明显小于标准砂场地。在0.2 g和0.3 g正弦波输入荷载下,珊瑚礁砂场地的加速度放大系数明显小于标准砂场地。0.05 g~0.3 g序列输入荷载下,珊瑚礁砂场地的累计地表沉降约为标准砂场地的2/3。场地液化后,珊瑚礁砂场地的剪应变要高于标准砂场地而剪应力小于标准砂场地。非液化土层,在0.2 g和0.3 g正弦波等强输入荷载下,珊瑚礁砂场地的剪应力和剪应变均小于标准砂。相同条件下,珊瑚礁砂场地的剪切模量随剪应变的衰减速率要快于标准砂场地。0.05 g~0.3 g序列输入荷载下,珊瑚礁砂场地的阻尼比均略小于标准砂场地。研究成果为认识珊瑚礁砂场地的液化特征和港口工程抗液化性态设计,提供了重要指导依据和丰富数据。

The liquefaction characteristics and anti-liquefaction treatment measures of coral sand sites are one of the key issues in the construction of tropical ports.Based on the dynamic centrifuge model parallel test,the seismic liquefaction characteristics of coral sand and standard sand in free fields are analyzed from the aspects of excess pore water pressure ratio,site amplification effect,surface subsidence,shear modulus and damping ratio.The results show that the load intensity triggering liquefaction of coral sand site is significantly higher than that of standard sand site,and the liquefaction depth is significantly lower than that of standard sand site under the same conditions.The acceleration amplification coefficient of coral sand site is obviously smaller than that of standard sand under the loads of 0.2 g and 0.3 g sine wave.The cumulative surface subsidence of coral sand site is about 2/3 of that of standard sand site under 0.05 g–0.3 g sequence loads.In liquefied soil layer,the shear strain of coral sand site is higher than that of standard sand site and the shear stress is lower than that of standard sand site.In the non-liquefied soil layer,under the strong loads of 0.2 g and 0.3 g sine wave,the shear stress and shear strain of coral sand site are smaller than that of standard sand.The attenuation rate of shear modulus of coral sand site with shear strain is faster than that of standard sand site under the same conditions.The damping ratio of coral sand site is slightly smaller than that of standard sand site under 0.05 g–0.3 g sequence loads.The research results provide important guidance basis and rich data for understanding the liquefaction characteristics of coral sites and designing the anti-liquefaction behavior of port engineering.