Experimental Study On the Effect of Hydrate Filling On the Mechanical Properties of Marine Sediments in the Shenhu Area, South China Sea

Abstract

The basic physical properties of marine sediments are analyzed by in situ sampling of marine sediments in the Shenhu area of the South China Sea. Marine sediment samples containing hydrates were prepared, and triaxial mechanical experiments were carried out under different conditions to analyze the evolution characteristics of the stress, strain, and porosity of the samples during loading. The results show that the marine sediment is characterized by weak cementation and a high mud content. The main components of the marine sediment are quartz, clay minerals, and calcite. The stress–strain curves of HBS samples show nonlinear deformation characteristics of weak elasticity and strong plasticity. Under the conditions of a low initial pore ratio, low effective confining pressure, and high hydrate saturation, strain softening and volume dilatancy characteristics are evident in the late loading stage. When the pores are filled with hydrate, the loading process is accompanied by fragmentation and detachment of hydrate crystals, resulting in a higher hydrate saturation, more severe shear dilatancy and strain softening of the sample, and more difficulty reaching the critical state of the sediment. With increasing effective confining pressure and hydrate saturation, the initial tangential modulus of the HBS samples shows a linear increase and the peak strength of the HBS sample increases nonlinearly. With increasing hydrate saturation, the cohesion values of the samples show a linear increase and the internal friction angles show an exponential increase. With the increase in the average normal stress, the critical differential stress shows a nearly linear increase and the critical void ratio shows a nearly linear decrease.