含碳酸盐混合砂的三轴剪切试验研究

Carbonate-containing mixed sand, as a special geotechnical material, is mainly distributed in tropical coastal areas. Its unique origin and structure endow it with geotechnical engineering properties different from those of terrigenous sand. For the mixed sand prepared according to different mass percentages from coral sand taken from the South China Sea of China and quartz sand taken from the Yangtze River Basin, triaxial consolidated drained shear tests under different confining pressures were carried out to study the shear characteristics of the mixed sand with different calcium carbonate contents. The results show that: (1) The peak strength of the mixed sand increases approximately linearly with the increase of the effective confining pressure and the calcium carbonate content; (2) The confining pressure and the carbonate content are the main parameters affecting the dilatancy characteristics of the mixed sand. With the increase of the carbonate content, the dilation-shrinkage conversion point and its corresponding axial strain increase; (3) With the increase of the carbonate content, the cohesion of the mixed sand shows a linear increasing trend, and the peak internal friction angle φf increases slowly; (4) The relative breakage rate Br of the mixed sand increases with the increase of the calcium carbonate content and the confining pressure.

含碳酸盐混合砂作为一种特殊的岩土材料主要分布于热带沿海地区,独特的成因和组构使得其具有不同于陆源砂的岩土工程特性。针对取自我国南海的珊瑚砂与取自长江流域石英砂按不同质量百分比配制而成的混合砂,开展不同围压下的三轴固结排水剪切试验,研究不同碳酸钙含量混合砂的剪切特性。结果表明:(1)混合砂峰值强度随有效围压和碳酸钙含量的增加呈近似线性增长;(2)围压及碳酸含量是影响混合砂剪胀特性的主要参数,随着碳酸盐含量的增加,胀缩转换点及其对应的轴向应变量增大;(3)随着碳酸盐含量的增加,混合砂的黏聚力呈线性增加趋势,峰值内摩擦角j f缓慢增长;(4)混合砂的相对破碎率Br随碳酸钙含量及围压的增加而增加。