【作者】 赵宝友；

【导师】 马震岳；

【作者基本信息】 大连理工大学 ， 水利水电工程， 2009， 博士

【摘要】 近年来,随着我国西部大开发战略的深入推进,数十座大型水电站工程在我国西部的地震高烈度聚集区和频发区正在或即将兴建。受地形等条件的限制,这些水电站的引水发电建筑物往往布置在地下岩体中,形成超大型的岩体地下洞室群。由于这种大型的岩体地下洞室群在空间上表现为大跨度、高边墙和长轴线的特点,那么,如何确保这类大型岩体地下洞室群在地震荷载作用下,尤其是强震作用下的动力稳定性,是工程设计中急待解决的关键问题。因此,本文以动力非线性有限元程序ABAQUS为平台,对水电站厂房岩体地下洞室群地震响应的数值模型、计算方法和影响因素进行了系统研究,并在此基础之上,提出了水电站厂房这类大型岩体洞室的减震方法。首先,建立了适合岩体地下洞室群静动力分析的有限元-无限元(FE-IE)耦合计算模型。基于该FE-IE耦合计算模型,通过数值解答与解析解答的对比分析,验证了ABAQUS中隐式和显式两种动力模块求解半空间散射场波动问题的精确性和可行性,进而证明了该耦合计算模型在地下洞室静动力分析研究领域的良好应用前景。之后系统研究了洞室埋深、地应力、岩体强度和断层破碎带这些地质因素对岩体洞室动力响应的影响。计算表明,洞室的埋深、地应力状况、岩体强度和断层破碎带在不同程度上都会影响着岩体洞室的地震响应。其次,从理论分析的角度,通过对损伤塑性模型基本理论及其适用条件的分析,阐明了损伤本构模型用于岩体地下洞室动力特性研究的理论适应性,并将此损伤塑性本构模型用于水电站厂房岩体地下洞室结构地震响应的研究。实例分析表明,损伤塑性模型能考虑地震等循环动荷载作用下岩体刚度退化和应变率的影响,能很好地描述混凝土、岩体等脆性材料的力学损伤行为,适合在岩体地下洞室抗震分析中应用。对于平行并排布置的水电站厂房岩体地下洞室群来说,当洞室群间距小于一倍洞室特征长度时(洞室特征长度定义为洞室群中相邻洞室最大的洞室跨度),洞室间距显著影响着洞室群的稳定性;当洞室群相邻洞室围岩厚度超过临界洞室间距时,洞室群稳定性受洞室间距的影响较小;对于一般工程的岩体来说,当洞室间距超过两倍的洞室特征长度时,结合合理的支护方式和抗震措施,洞室群的稳定性在一定程度上足可以得到满足。再次,考虑到水电站厂房岩体洞室轴线尺寸较长和地震动空间非均匀性的特点,研究了行波激励下这类大型岩体洞室的动力非线性响应。地震动行波激励下,洞室轴向各点的地震响应存在一定的相位差。地震动幅值是造成地下洞室发生破坏的关键因素,对于水电站厂房这类长轴线(轴线长度为300～400 m)的大型岩体地下洞室来说,小幅值地震动的行波效应对地下洞室破坏未产生明显影响,此时可不考虑地震动行波效应;然而,强震的行波效应对地下洞室破坏影响十分显著,此时应考虑强震动行波效应。随后,针对爆炸荷载这一特殊的高频动荷载,研究了水电站厂房岩体洞室的抗爆性能。浅埋深的洞室抗爆性能较差,深埋深的洞室抗爆性能较强。当侧压系数小于1时,随侧压系数的增加,洞室的抗爆性能变化并不明显;当地应力侧压系数大于1后,由于洞室稳定性受水平向地应力影响较大,随侧压系数的增加,洞室的抗爆性能显著降低。由于洞室拱顶效应影响,实际工程应加强对洞室拱肩、拱顶、底脚的加固支护,特别是洞室的拱肩部位。最后,针对水电站厂房这类大型岩体洞室,提出了采用设置柔性隔震垫层、注浆加固层和轴向隔震缝的减震措施,并分别对柔性隔震垫层、注浆加固层和轴向隔震缝的减震效果进行了敏感性分析。研究结果表明,硬岩洞室采用柔性隔震垫层的减震效果比较理想;软岩洞室采用注浆加固层的减震效果最佳;设置轴向隔震缝更有利于提高洞室结构的抗震性能。尽管设置柔性垫层后没有从根本上改变岩体洞室结构的动力特性,但设置一定厚度的柔性隔震垫层后不仅能充分发挥岩体洞室围岩的自承能力,而且还能明显地减小混凝土衬砌的动力反应。注浆加固层在很大程度上能减轻软岩洞室结构的地震反应。相邻机组段之间设置隔震缝不仅能降低施工期间混凝土所产生的干缩裂纹,而且在地震动期间还能显著降低混凝土衬砌的地震应力。本文提出的减震措施为后续类似工程的隔震和减震设计提供了方向。更多还原

【Abstract】 Along with the deeply advancement of the western development drive, a lot of huge hydraulic power plants are being built or will be built in China’s western regions which are seismically active zones with high earthquake intensity. For the reason of the restriction of geological condition, the diversion structures of the plants are mainly constructed in the mountains beside the rivers. Thus, the large rock cavern groups is formed. Its main features of this kind of large rock cavern groups are large span, long axial-length and high side walls. Therefore, how to ensure the safety of rock cavern groups under the action of earthquake, especially under the action of strong earthquake is one of the most important problems that should be solved properly and quickly. Taking the dynamic nonlinearity program ABAQUS as the numerical tool, firstly, the numerical model and other influenced factors are fully studied for the rock cavern groups under the action of seismic motion. Then, a seismic resistance measure is proposed for this large scale rock cavern groups.Firstly, in the precondition of using infinite elements as dynamic boundary condition, the comparison between the numerical solution and analytical solution proved the feasibility that ABAQUS can effectively simulate the wave propagation in half space scattered field. A coupling model of finite element and infinite element for the seismic response analysis of rock cavern groups is presented using the nonlinear finite program ABAQUS. On the basis of the propoed coupling model, the influence of geologic conditions such as embedded depth, geotress, strength of rocks and fracture zone on the seismic response of rock cavern is studied. The simulated results indicate that the geologic conditions motioned above can affect the seismic response of rock cavern groups in certain degree.Secondly, from the view of theoretical analysis, the applicability that the concrete damaged plasticity model could be used to study the dynamic property of surrounding rocks is analyzed. On the basis of this damaged plasticity model, the seismic response of rock cavern in a hydraulic power plant is studied. The numerical results indicate that the damaged plasticity model is suitable for the dynamic analysis of rock cavern subjected to earthquake. The model can also consider the stiffness recovery effects and rate sensitivity during cyclic loading. The results of the influence of cavern spacing on the stability of large cavern groups in a hydraulic power station indicate that the cavern spacing does have some influence on the stability of large cavern groups under the action of earthquake. If the cavern spacing is less than one cavern characteristic length (taken to the biggest width of a cavern in the group), the stabilities of adjacent caverns are significant affected by their spacing. Once the spacing exceeds the critical cavern characteristic length, the spacing hardly influences the stability of rock cavern groups. The stabilities of the cavern groups can be assured if the thickness of rocks between the adjacent caverns exceeds the critical cavern spacing in the conditions of adopting appropriate supporting schemes and effective anti-seismic reinforcement.Then, the dynamic nonlinear response of the rock cavern is studied subjected to seismic motion considering wave passage effect. The research shows that the wave passage effect of earthquake can result in phase difference of seismic response along the axial direction of the rock cavern. The amplitude of earthquake motion is the critical factor for the damage of rock cavern. For the rock cavern with its axial length around 300 m～400 m, the wave passage effect of weak earthquake can hardly influence the damage of rock cavern and the wave passage effect of strong earthquake can dramatically aggravate the damage of rock cavern.After that, the blast resistance of rock cavern is studied under the action of explosion loading. Numerical results indicate that the weak performance of blast resistance for the shallow cavern and the strong performance of blast resistance for the deep embedded cavern. Numerical results also indicate that when the geo-stress lateral pressure coefficientλis less than 1, no obvious variation of the blast resistance performance appears for the cavern. Onceλis great than 1, the blast resistance performance of the cavern is dramatically decreasing along with the increasing ofλ. For the effect of arch crown, the locations of spandrel, arch crown and arch footing should be enforced properly in practical engineering, especially the location of spandrel. The simulated results can be as references to the design of this kind of underground rock cavern in a hydraulic power station.Finally, the seismic resistance measure is proposed that is adopting soft-seismic isolation layer, reforced grouting layer and seismic isolation gap to enhance the seismic resistance performance of rock cavern. Sensitivity analysis of seismic resistance measure is conducted for the rock cavern. Simulated results show that soft-seismic isolation layer is better for the earthquake resistance of hard rock cavern and reforced grouting layer is suitable for the earthquake resistance of soft rock cavern. The seismic isolation gap is benefit for the seismic resistance of rock cavern. However, despite the dynamic features of rock cavern have not been changed essentially by adopting soft-seismic isolation layer, not only the self-supporting performance of surrounding rocks could be realized, but also the seismic response of concrete liner could be reduced in certain degree. Reforced grouting layer can reduce the dynamic response of liner in soft rock cavern. The structural joint not only can decrease the desiccation cracks during the period of concrete shrinkage but also can result in the reduction of seismic response for concrete liner. The seismic resistance measure proposed here can lead a way for the similar projects in the design of earthquake resistance.更多还原