围压对含水合物沉积物力学特性的影响

Effect of confining pressure on mechanical behavior of methane hydrate-bearing sediments

将实验室人工合成天然气水合物与高岭土混合制成岩心样以模拟海底含水合物沉积层,在不同围压条件下,对不同高岭土体积含量的含水合物沉积物进行三轴压缩试验。试验结果表明,当围压较低时,含水合物沉积物试样破坏强度随围压的增大而增大;而随着围压的进一步增加,试样强度有平缓下降的趋势。围压对含水合物沉积物试样的初始弹性模量影响很小,而割线模量受围压的影响较大,割线模量先随着围压的增大而增大,达到峰值后逐渐降低。高岭土含量对含水合物沉积物的内摩擦角影响不大,但对黏聚力有一定影响,随高岭土含量的增加,沉积物强度增大。

Synthesized gas hydrate in lab was mixed with kaoline to form core samples,so as to simulate the hydrate-bearing sedimentary layers in the seabed.Under conditions of different confining pressure,triaxial compressive tests were conducted on hydrate-bearing sediments with different volume content of kaoline.The results show that：（1） The failure strength of gas hydrate-bearing sediments increases with the confining pressure at a low-pressure stage.The strength tends to decline gently with further increases of confining pressure.（2） The modulus of elasticity E0 keeps unchanged under various confining pressures.But the secant modulus E50 presents a great dependency on the confining pressure.Secant modulus increases to the peak and then decreases with the increase of confining pressure;（3） The internal friction angles of gas hydrate-bearing sediments are not sensitive to the volume ratio of kaoline,but its cohesion depends on the volume ratio of kaoline.The sediment strength increases with the increase of kaoline content.