密实度对含水合物土体力学特性的影响

利用项目团队搭建的含天然气水合物土水–力特性联合测试装置,通过富气法制备含天然气水合物沉积物试样,采用三轴压缩试验研究了密实度对含水合物土体的力学特性的影响规律。试验结果表明,密实度对含水合物土体的应力–应变曲线、刚度和强度存在显著影响;在低净围压下,高密实度含水合物土会出现应变软化现象,而中、低密实度含水合物土出现应变硬化现象,并且剪缩程度随着密实度的增加而降低;含水合物土体的刚度会随着密实度的增大而增强,这种增强效应会随着净围压的增加逐渐减弱;在密实度越高的情况下,胶结赋存模式的水合物越多,但剪切行为也会破碎更多的水合物,这两者行为共同影响了含水合物土体的强度。因此,含水合物土体在中密实度情况下的强度最高。

EFFECT OF COMPACTNESS ON THE MECHANICAL BEHAVIOR OF HYDRATE-BEARING SOIL

Using the joint testing device of soil-water-force characteristics of natural gas hydrate built by the project team, the sediment samples of natural gas hydrate were prepared by gas-rich method, and the effect of compactness on the mechanical properties of hydrate-bearing soil was studied by triaxial compression test. The test results show that the compactness has a significant effect on the stress-strain curve, stiffness and strength of hydrate-bearing soil, and strain softening occurs in high-density hydrate-bearing soil under low net confining pressure. on the other hand, the hydrate soil with medium or low density appears strain hardening, and the degree of shear thinning decreases with the increase of compactness. The stiffness of hydrate-bearing soil will increase with the increase of compactness, and this enhancement effect will gradually decrease with the increase of net confining pressure; in the case of higher density, more hydrate exhists in the cementation mode, however shearing tends to break more hydrate. Both affect the strength of hydrate-bearing soil. Therefore, the strength of hydrate-bearing soil is the highest in the case of medium density.