地震破裂过程的数值模拟通常是假定破裂发生在先存断层上.但是,实际地震过程中,除了沿着先存断层产生自发破裂外,很有可能会产生新的破裂.为此,本文将传统有限元与扩展有限元方法(Extended Finite Element Method,XFEM)相结合,首先利用...地震破裂过程的数值模拟通常是假定破裂发生在先存断层上.但是,实际地震过程中,除了沿着先存断层产生自发破裂外,很有可能会产生新的破裂.为此,本文将传统有限元与扩展有限元方法(Extended Finite Element Method,XFEM)相结合,首先利用传统有限元方法模拟先存断层上的自发破裂过程,随后采用扩展有限元方法模拟不同介质(内摩擦角分别为0°、22.5°和45°)中,由于先存断层破裂造成的断层尖端应力集中导致的新生破裂过程.当内摩擦角为0°时,2条新生破裂与先存断层走向之间的夹角分别为0°和90°;当内摩擦角为22.5°时,该夹角变为11.25°和78.75°;当内摩擦角为45°时,该夹角变为22.5°和67.5°.在这三种情形下,新生的2条破裂,相互垂直,但破裂特征(破裂长度及破裂速度)不同,与先存断层之间的夹角越小的新生破裂,其扩展距离越远,扩展速度也更快(甚至为超剪切破裂).此外,在模拟结果中,岩石强度越低,断层扩展的长度越长,扩展速度也越快.本研究对于地震破裂全过程的数值模拟、深刻认识地震震源过程、断层生长以及地震灾害评估等有着重要的科学意义.展开更多
为研究冻胀荷载对双裂隙岩体裂纹扩展及贯通机制的影响,文章基于扩展有限元法(extended finite element method,XFEM),分析冻胀力作用下不同岩桥参数双裂隙试样的裂纹扩展特征和破坏形式,探究在冻胀力和侧向卸荷共同作用下双裂隙试样的...为研究冻胀荷载对双裂隙岩体裂纹扩展及贯通机制的影响,文章基于扩展有限元法(extended finite element method,XFEM),分析冻胀力作用下不同岩桥参数双裂隙试样的裂纹扩展特征和破坏形式,探究在冻胀力和侧向卸荷共同作用下双裂隙试样的裂纹扩展贯通规律。结果表明:基于XFEM的数值模拟结果与试验中的裂纹扩展路径基本吻合,验证了XFEM能够有效地应用于双裂隙岩体的裂纹扩展模拟;非岩桥区冻胀裂纹的扩展方向与预制裂隙走向相同,而岩桥区裂纹的扩展方向受到冻胀应力的影响,裂纹扩展方向偏向于另一条预制裂隙位置;冻胀裂纹的扩展模式受到围压的影响,随着围压增加,侧向卸荷过程中裂纹扩展模式由拉张模式变成拉剪混合模式,裂纹扩展方向也发生偏转。研究方法和结果可为低温裂隙岩体裂纹扩展相关研究提供参考。展开更多
A unit cell including the matrix, precipitation free zone(PFZ) and grain boundary was prepared, and the crystal plasticity finite element method(CPFEM) and extended finite element method(XFEM) were used to simulate th...A unit cell including the matrix, precipitation free zone(PFZ) and grain boundary was prepared, and the crystal plasticity finite element method(CPFEM) and extended finite element method(XFEM) were used to simulate the propagation of cracks at grain boundary. Simulation results show that the crystallographic orientation of PFZ has significant influence on crack propagation, which includes the crack growth direction and crack growth velocity. The fracture strain of soft orientation is larger than that of hard orientation due to the role of reducing the stress intensity at grain boundary in intergranular brittle fracture. But in intergranular ductile fracture, the fracture strain of soft orientation may be smaller than that of hard orientation due to the roles of deformation localization.展开更多
文摘地震破裂过程的数值模拟通常是假定破裂发生在先存断层上.但是,实际地震过程中,除了沿着先存断层产生自发破裂外,很有可能会产生新的破裂.为此,本文将传统有限元与扩展有限元方法(Extended Finite Element Method,XFEM)相结合,首先利用传统有限元方法模拟先存断层上的自发破裂过程,随后采用扩展有限元方法模拟不同介质(内摩擦角分别为0°、22.5°和45°)中,由于先存断层破裂造成的断层尖端应力集中导致的新生破裂过程.当内摩擦角为0°时,2条新生破裂与先存断层走向之间的夹角分别为0°和90°;当内摩擦角为22.5°时,该夹角变为11.25°和78.75°;当内摩擦角为45°时,该夹角变为22.5°和67.5°.在这三种情形下,新生的2条破裂,相互垂直,但破裂特征(破裂长度及破裂速度)不同,与先存断层之间的夹角越小的新生破裂,其扩展距离越远,扩展速度也更快(甚至为超剪切破裂).此外,在模拟结果中,岩石强度越低,断层扩展的长度越长,扩展速度也越快.本研究对于地震破裂全过程的数值模拟、深刻认识地震震源过程、断层生长以及地震灾害评估等有着重要的科学意义.
文摘为研究冻胀荷载对双裂隙岩体裂纹扩展及贯通机制的影响,文章基于扩展有限元法(extended finite element method,XFEM),分析冻胀力作用下不同岩桥参数双裂隙试样的裂纹扩展特征和破坏形式,探究在冻胀力和侧向卸荷共同作用下双裂隙试样的裂纹扩展贯通规律。结果表明:基于XFEM的数值模拟结果与试验中的裂纹扩展路径基本吻合,验证了XFEM能够有效地应用于双裂隙岩体的裂纹扩展模拟;非岩桥区冻胀裂纹的扩展方向与预制裂隙走向相同,而岩桥区裂纹的扩展方向受到冻胀应力的影响,裂纹扩展方向偏向于另一条预制裂隙位置;冻胀裂纹的扩展模式受到围压的影响,随着围压增加,侧向卸荷过程中裂纹扩展模式由拉张模式变成拉剪混合模式,裂纹扩展方向也发生偏转。研究方法和结果可为低温裂隙岩体裂纹扩展相关研究提供参考。
基金Projects(51475162,51405153)supported by the National Natural Science Foundation of ChinaProject(14JJ5015)supported by the Hunan Provincial Natural Science Foundation,China
文摘A unit cell including the matrix, precipitation free zone(PFZ) and grain boundary was prepared, and the crystal plasticity finite element method(CPFEM) and extended finite element method(XFEM) were used to simulate the propagation of cracks at grain boundary. Simulation results show that the crystallographic orientation of PFZ has significant influence on crack propagation, which includes the crack growth direction and crack growth velocity. The fracture strain of soft orientation is larger than that of hard orientation due to the role of reducing the stress intensity at grain boundary in intergranular brittle fracture. But in intergranular ductile fracture, the fracture strain of soft orientation may be smaller than that of hard orientation due to the roles of deformation localization.
