Experimental Study on Consolidation Properties of Hydrate-Bearing Fine-Grained Sediments Collected from the Shenhu Area of the Northern South China Sea

Mechanical properties of hydrate-bearing fine-grained sediments are crucial to effectively mitigate environmental risks caused by artificial and natural decomposition of natural gas hydrates, and the decomposition can induce laterally confined deformation. To explore the effect of natural gas hydrates on laterally confined compression properties, consolidation tests are conducted on remolded hydrate-free and hydrate-bearing samples by using natural fine-grained sediments collected from the northern South China Sea as the host sediments, and empirical equations are developed based on the analyses of consolidation characteristics. The results show that vertical loading induces a reduction in void ratio, and the reduction increases with decreasing hydrate saturation when samples are subjected to the same vertical stress change. The compression index of samples is about 0.53 whether there is hydrate or not, but the yield stress of samples increases sharply with increasing hydrate saturation once beyond the critical value. The coefficient of volume compression and the coefficient of consolidation of hydrate-bearing samples both increase firstly and then decrease to a relative stable level with increasing vertical stress, and the transition occurs at 200 kPa. The average consolidation degree with elapsed time increases rapidly under low vertical stresses, slowly under median vertical stresses, and under high vertical stresses, the consolidation increases a little faster but still slower than those under low vertical stresses.