胶结型含可燃冰砂土剪切特性的离散元模拟  

DISCRETE ELEMENT SIMULATION OF THE SHEAR BEHAVIOR OF CEMENTED METHANE HYDRATE-BEARING SANDS

作　　者：王璇 徐明[1] WANG Xuan;XU Ming(Department of Civil Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学土木工程系,北京100084

出　　处：《工程力学》2021年第2期44-51,共8页Engineering Mechanics

基　　金：国家自然科学基金项目(51978382);国家973计划项目(2014CB047003)。

摘　　要：可燃冰是一种新型清洁能源,广泛分布于深海土体和常年冻土中,对其开采需要深入认识含可燃冰土体的力学特性。该文提出了一种胶结型含可燃冰砂土离散元模型建立方法,并利用该模型完成了排水双轴剪切试验的模拟。通过与前人试验数据对比,验证了该离散元模型的准确性,结合该模型分析了剪切过程中含可燃冰砂土的宏细观变化规律。结果表明:砂土抗剪强度、应变软化特性及剪胀性均随可燃冰饱和度的增加而增加;可燃冰胶结断裂数量的演化与偏应力紧密相关,偏应力达到峰值时胶结断裂数量增长速率最快;剪切过程中剪切带内外土体的胶结断裂、颗粒运动、孔隙率变化均表现出明显的差异。通过对模型粘结断裂率、剪切带内外局部孔隙率等细观指标的分析,对土体的偏应力变化、体积变化等宏观现象的机理做出了更进一步的阐释。The methane hydrate is a new type of clean energy,and is widely distributed in deep sea sediments and permafrost.It is necessary to study the mechanical properties of the methane hydrate-bearing sands.In this paper,a method of generating the discrete element model of cemented methane hydrate-bearing sands is proposed.The model is used to simulate a drained biaxial test.The accuracy of the discrete element model is verified by comparing it with previous experimental data.The macro and micro characteristics of the methane hydrate-bearing sands are then analyzed using the model.The results show that the shear strength,strain softening characteristics and dilatancy of the sand increase with the increase of methane saturation,that the evolution of the hydrate fracture number is closely related to the deviator stress,that the hydrate fracture number increases most rapidly when the deviator stress reaches the peak value,and that the hydrate fracture,particle movement and the porosity change inside and outside the shear band during the test are obviously different.Through the analysis of some micro indexes such as the bond breaking ratio and local porosity inside and outside the shear band,the mechanism of the macro behavior such as the deviator stress and volume change of the methane hydrate-bearing sand is further explained.

关 键 词：可燃冰 砂土 离散单元法 剪胀性 剪切带 

分 类 号：TU43[建筑科学—岩土工程]