Study On Constitutive Model And Static Cone Penetration System Of Natural-Gas-Hydrate Sediments

With the rapid development of science and technology and the continuous progress of human society,the global demand for energy is increasing.As many traditional resources are also becoming exhausted,humanity is now facing a severe energy crisis.In recent years,Natural Gas Hydrates(NGH),as the substitute for traditional energy sources such as petroleum,have drawn the extensive attention of many scholars.However,due to the limitation of storage conditions,the environment and operation accidents caused by hydrate decomposition are easy to be caused during mining.Therefore,it is of great practical significance to study the physical properties and mechanical behavior of hydrate-bearing sediments.On the basis of numerous previous scholars' studies concerning to the mechanical properties of NGH sediments,this paper introduces the concept of Lode Angle and hydrate saturation parameter to establish the ideal elastic-plastic constitutive model of NGH sediments in terms of modified Mohr-Coulomb criterion.From the perspective of completely implicit backward Euler algorithm,the stability and applicability of this UMAT subroutine model was verified by three-units testing experiments proposed in the ABAQUS' user manual after its programming through using Fortran language.According to the secondary development interface provided by ABAQUS software for users,this paper carries out numerical simulation analysis of the static cone penetrating test process by using ABAQUS software as an analysis platform to call the UMAT subroutine of NGH sediments and obtains the curves of cone tip resistance and side friction resistance at different penetration depths.Finally,the author designs a set of static cone penetrating system project,which is through loaded-Underwater Remotely Operated Vehicles(ROV)to detect the deep-sea gas hydrates.This project mainly includes the structural design of sensor probe as well as the program selection of auxiliary system,to obtain optimized project of sensors' measuring via ANSYS Workbench.This paper sets up a testing platform of simulating the NGH sediments' cone penetration testing process by using the laboratory's existing equipment and instruments.The experimtental result shows that the curves of the cone tip resistance and side frictional resistance are basically consistent with the values of finite element analysis,also consistent with the experimental results from the French scholar Kelize.This proves the correctness and effectiveness of the model established in this paper.The work of this paper enriches the material base of ABAQUS software,which has important reference value for the numerical simulation study of NGH sediments in the later stage.