Stability Analysis And Landslide Prediction Of Submarine Slopes Containing Natural Gas Hydrates

Hydrate decomposition can induce submarine slope instability and damage submarine engineering facilities.The instability of gas-bearing hydrate formation is one of the potential conditions for triggering deep water engineering disaster.The evaluation of slope stability considering hydrate decomposition is an important problem in marine geology disaster research.At present,the research on the stability analysis of submarine slope mainly considers the weakening of reservoir strength caused by hydrate decomposition and the uneven distribution of soil layer strength separately.And there is less research on the potential disaster area of undersea landslide in hydrate rich area.According to the engineering geological characteristics of hydrate rich area in shenhu sea area of the south china sea,this paper takes into account the variation of non-drainage shear strength along the depth of superjacent layer,carries out the stability evaluation of submarine slopes with hydrates layer and makes the prediction of potential landslide after sliding.The main research results are as follows:The most dangerous sliding surfaces of the submarine slopes with hydrate layers in the study area are mainly presented in two ways,one is located at the upper lamination and the other is on the top boundary of hydration layers.When hydrate decomposition is not considered,the stability of the submarine slope is mainly controlled by the slope gradient and soil mass strength,and it mainly manifests as shallow landslide.When considering the decomposition of hydrates,the weakening of the hydrate reservoir leads to an impact on the overall slope stability,however,the position of the most dangerous sliding surface under the same condition is greatly affected by the depth of hydrate layer,and there is a critical depth controlled by topography geometry and overlay strength.Hydrate decomposition has little effect on slope stability when buried depth is greater than critical burial depth.The most dangerous sliding surface is located in the upper shallow stratum,which shows shallow surface failure.Less than the critical burial depth,the most dangerous sliding surface position passes through hydrate layer and manifests as deep landslide.According to the buried depth condition of hydrate layer in the current model,the safety coefficient of deep sliding surface is still higher than that of shallow strata,which means that the impact of the shallow seabed landslide disaster needs to be paid more attentionTaking the acoustic profile of a real submarine slope with hydrate reservoir as an example,BING software is used to simulate the motion state of the calculated potential seabed landslide.The results show that the slip body under remolding has the characteristics of high flow velocity,wide slip distance and low thickness compared with the original slide body.The higher the sensitivity,the greater the initial strength of the landslide,and the thicker the sediments tend to form in flat,low-lying areas or when they climb.The greater the water content,the more fluidity of the landslide,and the larger the velocity and distance between the end and sliding,then the effect of topographic modification and damage of submarine engineering facilities on the maximum velocity of migration will be increased.The results can provide some references for the prediction of potential landslide disaster area and disaster protection in the study area.