钙质砂剪切特性试验研究

 对取自南沙群岛永暑礁附近海域的钙质砂进行了不同围压下的三轴排水剪切试验，试验结果表明，钙质砂在三轴剪切试验中的应力–应变关系随围压而发生变化，在低压时与普通陆源砂相近，而在中、高围压时表现出陆源砂高围压时的力学性质。在剪切过程中由于颗粒破碎导致封闭的内孔隙释放，体积应变要比石英砂大得多，剪切过程中发生的变形几乎全为不可恢复的塑性变形，其剪胀性与峰值应力比与围压密切相关，峰值应力比与剪胀性随着围压的升高而下降。

EXPERIMENTAL RESEARCH ON SHEAR BEHAVIOR OF CALCAREOUS SAND

The results of drained shear tests carried out on calcareous sand sample from the South China Sea were presented. The tests reveal that the relation between the stress and strain changes when the confining pressures are changed. Under low pressure，it is similar to the terrigenous sand；and under the medium confining pressure，the mechanical property of the calcareous sand is just analogous with that of the terrigenous sand under high stress level. The particle breakage results in liberation of the close interspace. Thus the volume of strain is much larger than that of quartz sand，which makes almost all the deformation irreversibly plastic during shear process. And the results also indicate that the dilatancy and ratio of stress are closely related to the confining pressures，they decrease as the confining pressures increase.