循环荷载作用下钙质砂液化及体变特性

Liquefaction characteristics and volume change of calcareous sand under cyclic loading

钙质砂是岛礁建设的重要材料之一,具有颗粒形状不规则与易破碎特性,钙质砂在动荷载下性质与石英砂有所区别,对钙质砂的液化特性及体变规律进行探究,能够更好地揭示钙质砂液化沉降规律。采用动三轴试验对饱和钙质砂进行了一系列不排水循环剪切试验。孔隙水压力的上升速率会影响钙质砂的抗液化性,实验结果表明:钙质砂孔隙水压力的上升速率受密实度、有效围压等因素影响。在动荷载作用下,试样上下孔隙水压力存在少量差值,同一试样上下孔隙水压力差受试样密实度、围压以及循环应力比影响。钙质砂在循环荷载作用下体变的主要影响因素是密实度,密实度越大,体变率也会越小,级配和围压对体变率的影响较小,且体变率较石英砂更低。

Calcareous sand is one of the important materials for the construction of island reefs,with irregular particle shape and easy to break,calcareous sand under dynamic load properties are different from quartz sand,the liquefaction characteristics and body change law of calcareous sand can be explored to better reveal the liquefaction settlement law of calcareous sand.A series of undrained cyclic shear tests were carried out on saturated calcareous sand by dynamic triaxial test.The rise rate of pore water pressure affects the liquefaction resistance of calcareous sand,and the experimental results show that the rise rate of pore water pressure of calcareous sand is affected by factors such as compactness and effective confining pressure.Under the cyclic loading,there is a small difference in the pore water pressure above and below the specimen.The pore water pressure above and below the same specimen is influenced by the specimen density,the effective confining pressure and the cyclic stress ratio.The main influencing factor of the volume change of calcareous sand under the cyclic loading is density,the greater the density,the smaller the volume change rate;the smaller the effect of grade and effective confining pressure on volume change,and the lower the volume change rate is lower than quartz sand.