Analysis Of The Influence Of Gas Hydrate Exploitation On Slope Stability Of Gas Hydrate Bearing Sediments

Under the background of increasingly severe energy crisis,countries all over the world are actively developing new energy.As a clean and efficient new energy,natural gas hydrate has been paid more and more attention.Natural gas hydrate mostly occurs in deep-sea seabed sediments or permafrost on the continental plateau,and the hydrate is very sensitive to its occurrence environment.Once the environment is disturbed,it is easy to cause large-scale decomposition,resulting in deterioration of the soil and a series of natural disasters such as submarine landslides.Due to the complexity of Hydrate Occurrence environment,the cost of trial and error mining is expensive.According to the actual geological conditions,the finite element model is established for numerical simulation,which provides a certain basis and reference for the safe and efficient exploitation of hydrate and the stability of deep-sea energy soil slope and related structures.Therefore,the following work has been completed in this paper:(1)The basic principle of strength reduction method is introduced,and the selection principle of instability criterion is determined.Based on ABAQUS software,the numerical implementation process of finite element strength reduction method is studied and verified by a slope example.(2)Based on the calculation model of excess pore water pressure proposed by Grozic,the formula for calculating excess pore water pressure according to the decomposition degree of hydrate is derived.In ABAQUS,the degradation of soil material properties caused by hydrate decomposition and the resulting excess pore water pressure are established.The theoretical analysis model of the submarine energy soil slope is used,and the effect of hydrate decomposition on the stability of the submarine slope is analyzed through the calculation results.(3)According to the different locations where natural gas hydrates occur on the submarine slopes,three different models were established to simulate the occurrence of hydrates on the top of the slope,the toe and the bottom of the slope.The effect of hydrate decomposition on the stability of submarine slopes when the storage location changes.(4)Simulate the hydrate mining in different areas of the slope by a single vertical well and the joint mining of multiple vertical wells.The mining range of the actual mining well is taken into account.The influence of single vertical well located in the front,middle and back area of the slope on the stability of the slope is analyzed through the calculation results,and the results are compared with the calculation results of multiple vertical wells,which provides a reference for the selection of hydrate mining area and the number of wells.