水合物形成对含水合物砂土强度影响

采用非饱和成样法（A法）和饱和试样气体扩散制样法（B法）两种试验室方法，合成了含CO₂水合物的砂土试样，并采用改造过的三轴剪切试验仪完成了相应的三轴剪切试验。实验结果表明：A法制得试样强度和刚度随水合物饱和度增大而增大，且相当敏感；而B法制得试样在水合物饱和度为19.44%与纯砂土的力学特征差别很小，在较高饱和度（26.73%）时，含水合物砂土的强度和刚度就有了较为明显提高；由此可以得出含水合物砂土的强度特征是水合物含量和水合物于砂土中赋存状态联合决定的；同时也发现随着水合物饱和度的增大，试样的剪胀性越来越明显。最后，通过对A法制得试样的强度参数分析表明：含水合物砂土的黏聚力随饱和度的增大而提高，而摩擦角基本不变。

Effect of hydrate formation on mechanical strength of hydrate-bearing sand

In order to evaluate the effect of hydrate formation on the mechanical strength of hydrate-bearing sand, a series of triaxial compression tests are conducted on the samples prepared by means of two different methods, namely, the partial water saturation method (A method) and the dissolved gas method (B method). The experimental results show that the strength and stiffness of the samples formed by A method increase sensitively with the saturation of hydrate, whereas those prepared by B method keep almost constant when the saturation of hydrate is less than 19%, and then increase significantly when the saturation of hydrate is higher than 27%. The results imply that the mechanical behaviors of the hydrate-bearing sand depend upon both the content and the distribution of hydrate in the pores. The hydrate-bearing samples tend to dilate when the saturation of hydrate increases. In addition, an analysis of experimental results of the samples prepared by the A method shows that the cohesion of the samples increases with the saturation of hydrate, while the frictional angle keeps practically constant.