含碳酸盐混合砂的三轴剪切试验研究

Experimental study of triaxial shear characteristics of carbonate mixed sand

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?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。

Mixed sand containing carbonate,as a special geo-material,is mainly distributed in tropical coastal areas.Its unique genesis and composite structure result in different geotechnical engineering characteristics compared to terrigenous sand.Triaxial tests were carried out on the mixed sand with different contents of calcium carbonate under different confining pressures.The testing materials were prepared with coral sand from the South China Sea and silicon sand from the Changjiang River with different mass percentages.The results show that:1)the peak strength increases approximately linearly with the increase of effective confining pressure and calcium carbonate content;2)confining pressure and carbonate content are the main parameters influencing the dilatancy characteristics of the mixed sand.The increase of carbonate content results in the transition point between dilation and contraction response and its corresponding axial strain to increase;3)with the increase of carbonate content,the peak value of cohesion increases linearly and the internal friction angle increase slightly;4)the relative crushing rate of mixed sand increases with the increase of the calcium carbonate content and confining pressure.