【作者】 刘宁；

【导师】 朱维申；

【作者基本信息】 山东大学 ， 工程力学， 2009， 博士

【摘要】 近年来,随着国民经济的持续稳定增长,国家对地下洞室开发利用的需求日益增加,大量工程都在建设或筹划中,地下工程建设呈现出方兴未艾的局面。仅就西部的水电工程来说,近些年内有相当多的大型水力发电工程和蓄能电站进入兴建与筹划期。其中很多都设计有大型或超大型地下洞室群做主要的水工建筑物,且大多选择为深埋式地下厂房。而西部地区具有全球最强烈的现代地壳运动,活动断裂发育,地质环境极为复杂,加上高山峡谷等地形地貌条件,往往赋存有高地应力场。在此条件下围岩的破裂现象在洞群施工期就会明显的出现,一系列大型洞群的高边墙经常发现有劈裂裂缝,并随着地下厂房规模的增大表现得更加突出。此现象已经引起专家的关注,但对其发生机理及其锚固效应尚未进行深入地分析研究。本文采用理论分析、数值模拟和实验验证相结合的方法,从微观和宏观两个方面系统研究了高地应力条件下围岩劈裂破坏机理及其锚固效应,并将理论分析与工程实践紧密结合,主要完成了以下几个方面的工作:(1)从断裂力学的角度,系统研究了地下工程围岩中的裂纹在各种受力条件下(包括拉剪、压剪两种情况)的起裂、扩展及贯通以致最终形成劈裂裂缝的各个阶段的特征和破坏判据。分析了裂纹之间的贯通机理和极值分布,从理论上揭示了多裂纹之间可能存在的贯通模式与机理。最后以受压岩体中的斜裂纹扩展过程分析为例,模拟了岩体中裂纹逐渐发展成劈裂裂缝的整个过程。(2)在有限元分析软件ANSYS中实现断裂分析的基本过程。通过参数化设计方法APDL编写裂纹扩展模拟的前处理程序,实现了裂纹断裂计算和分析的自动化,证明ANSYS非常适合于模拟含裂纹或缺陷结构,当参数选择合适时,有限元可以很好的模拟裂纹的扩展过程。并分别模拟了裂纹扩展的不同阶段,通过与理论计算结果相对照,进一步完善劈裂裂缝的形成过程和发生机理。(3)基于试验结果,分析研究了岩石的单轴压缩和三轴压缩条件下的变形破坏过程,揭示了这一过程的能量耗散及能量释放特征。通过实验室内的相似模型试验,研究了加锚对岩体断裂能的影响。为了能够定量分析围岩能量释放的程度,基于裂纹扩展是以能量释放为主要特征的破坏现象的认识,定量计算了能量释放率,并将其应用到瀑布沟地下厂房的开挖分析中,分别得到了该地下厂房不同位置处弹性能随开挖步变化曲线以及弹性能密度分布等值线图,可以更直观地分析能量与裂纹扩展的关系。(4)采用滑移裂纹组模型来模拟岩石在轴向压力作用下的劈裂破坏,以考虑裂纹之间的相互作用。基于裂纹扩展过程中的能量平衡原理,分别建立了线弹性条件下和小范围屈服条件下的劈裂判据。并将这两个判据应用到琅琊山抽水蓄能水电站的开挖分析中,分别计算得到了两种情况下劈裂破坏区范围分布图,以定量的概念和直观的图像来把握和判断围岩中不同区域的劈裂破坏程度,为高地应力条件下地下工程开挖过程中出现的劈裂破坏提高更加科学合理的预测判据。(5)对于处在高地应力下脆性围岩中的地下洞室群,开挖时洞室围岩容易出现纵向的劈裂裂缝,导致脆性开裂,形成劈裂性平行大裂缝组,可将其看作叠层薄板。根据柯克霍夫平板理论检验了薄板模型的适用性,在薄板模型的基础上利用能量方法建立了劈裂围岩的临界应力、位移的解析计算公式。以瀑布沟水电站为工程背景,将劈裂判据编成fish语言计算得到围岩的劈裂破损区。在此基础上利用薄板力学模型计算了其临界应力和最大位移。(6)锚喷支护对岩体的加固作用在很大程度上是抑制裂纹的扩展。分别采用理论分析和数值方法对锚喷支护抑制裂纹的扩展进行了分析研究。首先在理论方面利用断裂力学理论分别分析了混凝土喷层和锚杆对应力强度因子的影响,并计算得到了锚杆的最佳安装角。然后利用ANSYS数值模拟了锚杆对裂纹的止裂作用,分析了不同因素对应力强度因子的影响。(7)通过分别计算外力所做功,锚杆吸收的能量,塑性能,弹性应变能,裂纹扩展耗散的能量,根据能量守恒定律建立了锚固条件下围岩劈裂破坏判据,并将该判据应用到猴子岩水电站的开挖分析中,通过分别计算三种洞室间距方案、三种开挖顺序以及考虑锚杆作用下洞室围岩的劈裂破坏范围,并与计算的塑性区范围相对比,分析得出在高地应力条件下不能仅仅以塑性区作为评价开挖顺序和洞室布置方案的唯一指标,有时劈裂区更能反映出地应力分布的特征,可以为开挖方案的优化提供更多的参考意见。更多还原

【Abstract】 The demand for the underground caverns is increasing by the persistent national economy increase in recent years. A great deal of engineering is being built or planed. The underground engineering is in the ascendant. For western water-power engineering only, quite a number of large-scale water-power engineering and storage plants has been built and designed. Most of them use large or ultra-large underground caverns as hydraulic architectures and mostly are immerged. The western bears the most strong modern lithosphere movement. The geologic environment is very complicated. Because of the landform and physiognomy such as alp and canyon, there always is high geostress filed. There will be fracture phenomena in constructing under the condition. A series of high side wall were found splitting cracks and standing out by the scale. This phenomenon has attracted the expert’s attention. But the mechanism and anchorage effect has not been gone deep into analyze and research. The theory analysis, numerical simulation and experiment validation were combined in this thesis. The splitting failure mechanism and anchorage effect are systematically studied from both microcosmic and macroscopic aspect. Combine the theory analysis with engineering practice tightly. The main results discussed in this thesis are as follows:(1) Based on fracture mechanics, the characteristics and failure criterions of wall rock cracks including initiation, propagation, and coalescence are analyzed systematically under different conditions. The coalescence mechanism and extremum distribution of cracks are researched. The coalescence mode and mechanism among cracks are revealed in theory. Finally, take the compressed crack propagation analysis as an example, simulate the whole process that the cracks in rock develop into splitting cracks.(2) To realize the basic process of fracture analysis in ansys. The fore treatment program of crack propagation simulation is compiled by parameterization method of apdl. The calculation and analysis is automatic. Ansys is well for simulating the structures which contain cracks and bugs. When the parameters are suitable, the propagation of cracks can be simulated well in ansys. The different phases of crack propagation are simulated. To compare with the results by theory, perfect the formation process and mechanism of splitting cracks.(3) According to the results of experiments, the failure process of rock under uniaxial and triaxial compression is analyzed. The characteristics of energy dissipation and release in the process are revealed. Via the similar experiments in lab, the fracture energy of bolted rock mass is studied. In order to analyze the degree of released energy quantitatively, the ratio of energy release is computed based on the acquaintance to the failure phenomenon which the crack propagation give priority to the energy release. This method is applied into Pubugou power station excavation. Both the curves of elastic energy change in different positions and the contour chart of elastic energy density are received. The relationship between energy and crack propagation can be analyzed straightly.(4) In order to consider the interaction among cracks, adopt the sliding model of multi-cracks to simulate the splitting failure of rock in axial compress. According to the energy balance principle in the process of crack propagation, the splitting criterions under both linear elastic and small range yield are set up. Both of them are put into the excavation of Langyashan pumped storage power station. The distribution charts of splitting failure range are obtained. The splitting failure degree in different positions can be grasped and judged by quantificational concepts and intuitionistic images. The method offer more scientific and rational criterion to evaluate the splitting failure of underground engineering in high geostress.(5) When the underground caverns of brittle wall rock that locate in high geostress are being excavated, the longitudinal splitting cracks always present and lead to brittle craze. The splitting cracks will evolve into large parallel splitting crack groups. It can be treated as thin plate. According to G.R.Kirchoff thin plate theory, test the applicability of thin plate. The stress and displacement are resolved by elastic thin plate at the condition of basic hypothesis and geostress. The resolution calculation of critical stress and displacement are settled in theory based on energy method. Set Pubugou power station as engineering background. The criterion is programmed into fish language and the splitting failure range is confirmed. The critical stress and displacement are calculated by the resolution formula in the splitting failure range.(6) The reinforcement of bolts and shotcrete supporting to rock mass can control the cracks propagation well. Adopt both theory analysis and simulation method to study the mechanism of controlling the propagation. Firstly, from the theory aspect analyze the influence of shotcrete and bolts on stress intensity factor based on fracture mechanism theory. The best fixed angle of bolts is calculated. Then use ansys to simulate the crack arrest function of bolt to crack. Analyze the influence of different factors on stress intensity factor.(7) The splitting failure criterion of bolted rock mass is set up depending on energy balance principle including the work by external force, dissipation energy by bolts, plastic energy, elastic strain energy and dissipation energy by cracks propagation. The criterion is also applied into the excavation analysis of Houziyan water power station. The splitting failure range of surrounding rock is calculated, separately considering three separations, three excavation sequences and anchorage. And compare with the plastic range. The results show that the plastic range can not be treated as the only index which evaluates the excavation sequence and caverns layout scheme. The splitting failure may reflect more characters of geostress distribution sometimes and can give more reference opinions to optimization of excavation schemes.更多还原