【摘要】 首先验证基于离散元法的数值软件UDEC模拟应力波在岩体中传播的可行性。然后,运用离散元数值模拟技术,对应力波穿越不同产状大型结构面的传播特征进行探讨,并以龙门山地区的3条主要断裂对汶川地震应力波传播规律影响为实例加以说明,确认断裂隔震效应以及断裂上盘效应。研究结果表明:(1)应力波在结构面两侧造成的地表动力响应存在异常,靠近震源一侧的地表响应强烈;(2)结构面倾角对应力波的反射作用表现出随结构面倾角增大先增大后减小的趋势,随着结构面数量的增加,透过结构面的应力波产生的扰动越弱;(3)汶川地震中汶川—茂县断裂和灌县—安县断裂对汶川地震地震波具有明显的阻隔作用,使汶川—茂县断裂上盘靠近断裂的地表垂向加速度峰值比不存在断裂时降低38%,灌县—安县断裂下盘靠近断裂的地表加速度峰值则降低47%;(4)断裂对地震波的反射使得映秀—北川断裂上、下盘地表动力响应异常增强,与不存在断裂情况时相比,该断裂上、下盘两侧岩体的垂向加速度峰值分别升高了41%和32%。本研究结果反映断裂的隔震效应与上盘效应。更多还原

【Abstract】 First of all,the feasibility of using a universal distinct element code(UDEC) to simulate stress waves propagation in rockmass has been validated.Then,the study about the rules of stress waves crossing fractures which have various attitudes has been conducted.The three main fractures in Longmenshan region affecting the stress waves propagation are used as an example to validate the rules of stress waves crossing fractures and illustrate the shock isolation effects and the hanging wall effects of the large-scale fracture.The main research results can be summarized as follows:(1) The dynamic responses of the earth?s surface beside the fractures are anomalous compared with that on the fractures;and the dynamic responses of the earth?s surface on the side of hypocenter will be more seriously than that on the other side.(2) With the increasing of fractures attitudes from 0° to 90°,the shock isolation effects of fractures on stress waves firstly will increase and then will decrease;and the dynamic responses caused by transmitted waves will be weaker with the increasing of the amount of fractures.(3) Wenchuan—Maoxian fault and Guanxian—Anxian fault are not coseismic fault;so they have shown good shock isolation in the process of Wenchuan earthquake.Compared to the condition without faults,the vertical peak ground accelerations of hanging wall surface of Wenchuan—Maoxian fault and foot wall surface of Guanxian—Anxian fault decrease 38% and 47% respectively.(4) Because of the faults reflecting the earthquake waves,the dynamic responses of earth?s surfaces of the hanging wall and footwall of Yingxiu—Beichuan fault are serious compared to the state without faults.The vertical peak ground accelerations of the hanging wall and footwall surface of Yingxiu-Beichuan fault increase 41% and 32% respectively.The above research results reflect the shock isolation effect and hanging wall effect of fractures.更多还原