断层错动引起的上覆土体破裂演化规律研究

李秀菊　李鸿晶

摘要: 断层引起的地面永久大变形是工程特别是生命线工程地震破坏的重要原因之一, 而研究断层错动下上覆土体变形和破裂的发展演化规律, 则是预测地面永久变形状态和分析断层危害性的基础．本文采用有限元方法对垂直断层错动引起的上覆土体破裂演化规律进行了研究, 建立了垂直断层作用下上覆土体模拟的有限元模型, 对断层错动作用下上覆土体的破裂发展过程进行了模拟分析, 并分析了加载速率、土体特性及断层倾角等参数对上覆土体的破裂演化发展过程的影响．结果表明: ① 断层倾角越陡, 地表出现破裂时需要增加的垂直位移越大； ② 由于惯性力的影响, 断层加载速率对地表破裂所需施加位移和土层破裂角产生一定的影响； ③ 断层类型对土层地表破裂角与膨胀角、摩擦角之间的关系有很大影响．该分析结果可为新建工程的抗震设计和已建工程结构的抗震加固等工作提供依据．

关键词:

断层错动　土体破裂演化　数值模拟　有限元模型　参数影响

Abstract: Permanent ground deformation induced by fault movement is one of the main reasons for structural failure during an earthquake, especially for the failure of lifeline structures. Investigation of deformation and rupture propagation in overlying soil subject to fault displacements is the basis for predicting permanent ground displacements and analyzing fault risk. In this paper, rupture propagation in overlying soil under dip-slip fault displacements is investigated with finite element method, and a finite element model is developed for the overlying soil with excitation of the dip-slip fault displacement. The evolution of rupture propagation through overlying soil is simulated, and the effects of some parameters, such as loading rate, soil characteristics, dip angle of the fault, are estimated. The result shows ① the higher the dip angle of fault is, the bigger vertical displacement would be required to cause surface rupture; ② loading rate of the fault have some effects on the vertical displacement required to cause surface rupture and on rupture angle of soil because of inertial force; ③ the type of fault has significant effects on the relation between rupture angle of soil and dilatancy angle, as well as between rupture angle of soil and friction angle. The results presented in this paper could be referenced in earthquake resistant design of new structures and reinforcement of the existing structures.

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