摘要
基于“颗粒碎片替换法”建立反映颗粒破碎行为的含水合物沉积物基质离散元模型,与不破碎模型开展对比三轴剪切试验,证明颗粒破碎对强度和剪胀特征具有重要影响。进而应用“粒径膨胀法”提高模型对体应变和颗粒破碎程度的模拟效果,通过一系列低-高有效围压下的模拟三轴排水剪切试验,研究高应力范围及剪切过程中细观力学特征的演化。结果表明:随着有效围压逐渐增大,试样强度、刚度和平均法向接触力均增大,力链网络更加密集且由环状演变为以竖向为主,试样顶部与底部沿轴向运动的颗粒数量增加。颗粒破碎主要发生在剪切初期,力学配位数、平均法向接触力随剪切进行逐渐增大,剪切后期出现贯穿试样的强力链结构,颗粒运动逐渐从杂乱无章变为由顶、底两端向内,试样内部逐渐出现近似“X”形的剪切带。
Based on"particle fragmentation replacement method",a discrete element model is developed for hydrate-bearing sediment matrices,which can reflect the behavior of particle breakage.A comparative triaxial shear test is conducted for breakable and nonbreaking models,demonstrating that particle breakage has significantly influence on the strength and shear dilatancy characteristics.In addition,the"particle size expansion method"is applied to improve the simulation effect of the model on the volumetric strain and particle breakage degree.A series of simulated triaxial drainage shear tests are conducted under low and high effective confining pressures to evaluate the meso-mechanical characteristics.The results show that with the increase in the effective confining pressure,the strength,stiffness and average normal contact force of the specimen increase,and the force chain gradually is strengthened.The force chain network becomes denser and changes from annular to vertical,while the particles moving along the axial direction at both ends of the sample increase.The particle breakage primarily occurs during the early shearing.The mechanical coordination number and average normal contact force gradually increase with shearing.At the end of the shearing,A strong chain structure and an"X"shape shear band emerges within the sample,and the particles’motion varies from chaotic to top-and bottom-inward.
作者
徐爽
徐佳琳
许成顺
焦爽
Xu Shuang;Xu Jialin;Xu Chengshun;Jiao Shuang(Key Laboratory of Urban Security and Disaster Engineering,Ministry of Education,Beijing University of Technology,Beijing 100124,China;Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China)
出处
《太阳能学报》
EI
CAS
CSCD
北大核心
2024年第6期680-690,共11页
Acta Energiae Solaris Sinica
基金
国家自然科学基金杰出青年基金(52225807)。
关键词
天然气水合物
数值模拟
力学特性
砂土破碎
粒径膨胀法
natural gas hydrate
numerical simulation
mechanical properties
sand breakage
particle size expansion method
