【作者】 徐奴文；

【导师】 唐春安；

【作者基本信息】 大连理工大学 ， 岩土工程， 2011， 博士

【摘要】 岩质边坡失稳破坏(滑坡)是三大自然灾害之一,严重危及着国家财产和人民生命安全,边坡失稳预测研究是一项世界性的难题,迄今为止,仍然没有形成一套系统、完善和成熟的理论方法体系。岩质边坡失稳监测及预测分析一直是边坡工程稳定性研究的重要课题之一,也是岩石力学与工程领域的热点和难点。近年来,随着我国社会经济的稳健发展和对可再生清洁能源的大力需求,西南地区水电资源开发呈现加速发展的趋势,一大批大型(巨型)水电工程开始进行前期筹建、勘察设计或已经开工建设,这些水电工程都不可避免地面临高陡岩质边坡的安全稳定性问题。岩质高边坡的稳定问题不仅涉及到工程自身的安全,也涉及整体环境的安全。西南地区水利水电工程高陡岩质边坡的稳定控制已成为水电工程建设成败的关键技术问题之一,影响和制约着水力资源开发和水电工程建设。研究表明,岩质边坡失稳与其内部微震活动有着必然联系,微震活动是岩质边坡发生失稳破坏的前兆,失稳边坡内部微破裂演化先于地表位移发生。本文基于此学术思想,引入地震学理论和地球物理学方法,突破传统岩质边坡地表位移监测模式,通过采用微震监测系统实时获取边坡失稳前岩体内部的微震活动信息,建立岩质边坡有限元数值模型,通过大规模科学计算,解读岩质边坡失稳的应力场、微破裂演化规律,研究岩质边坡渐进破裂内部微震活动规律及其失稳机理,分析岩质边坡微破裂演化过程与应力场之间的联系,探索岩质边坡微破裂演化、繁衍对其宏观结构破坏过程中微震活动性的影响,包括边坡岩体破裂过程中的声发射时空分布规律及其失稳的前兆模式,寻求岩质边坡微震活动性、背景应力场演化与施工活动之间的联系,建立以微震现场监测为主、以背景应力场分析为辅的岩质边坡失稳预测方法。研究结果不仅可以揭示岩质边坡失稳本质,还能认清岩质边坡失稳破坏形成和发生的条件,还可为复杂应力条件下岩质边坡动态稳定性研究及其失稳预测提供新的思路和方法,对于减轻或避免岩质边坡失稳灾害、保障水电高陡岩质边坡工程施工与营运安全,具有一定的指导作用和现实意义。完成了以下主要研究内容：(1)成功构建锦屏一级水电站左岸边坡微震监测系统,初步实现左岸边坡稳定性及潜在风险区域的实时监测和分析。通过对左岸边坡地质、物探和施工资料的深入分析和现场踏勘研究,结合微震事件震源定位精度、监测系统灵敏度要求、工程条件以及边坡监测目的,进行了微震传感器的选型以及监测系统站网的优化研究,得到了满足技术经济要求的监测系统方案。(2)通过对岩质边坡不同震动信号的分析研究,提出结合现场踏勘、施工工况信息,综合运用时-频分析技术研究各种震动波形幅频特征的方法,得到了高陡岩质边坡岩石微破裂波形特征。通过人工敲击试验验证了微震传感器的灵敏性和准确性,采用人工定点爆破试验方法确定了左岸边坡等效整体波速模型,测试结果表明锦屏一级水电站左岸边坡微震监测系统定位精度完全满足现场工程要求,并分析了影响震源定位误差的主要因素。(3)通过微震活动性时空分布规律,研究了左岸边坡潜在破坏机理及其特征、施工、灌浆等响应区域,识别和圈定了左岸边坡深部岩体由于施工、爆破开挖和固结灌浆等诱发的损伤区域(断层和活化断层),为后期边坡工程的开挖、加固处理和常规监测加密部位提供参考。(4)利用真实破坏过程分析软件RFPA,研究了二维、三维条件下岩质边坡破坏过程微破裂的萌生、发育、扩展、相互作用和贯通的机理,探索了岩质边坡渐进破坏过程中应力场和微震活动性空间演化基本规律,形成从细观损伤演化过程揭示宏观岩体结构破坏的研究方法,从应力场演化和微震时空分布的层面上研究岩质边坡失稳的孕育和发生过程,再现了岩质边坡失稳灾变孕育过程中的应力积累、应力阴影和应力迁移等丰富现象。另外,将数值模拟得到的岩质边坡渐进破坏过程应力场与微震监测得到的施工扰动、断层和裂隙带等地质构造异常活化信息进行耦合分析,揭示了岩质边坡人工扰动作用引起构造活化和灾变的机制。针对左岸边坡现场出现的实际问题,通过微震监测和数值模拟耦合分析,解释了坝顶平台裂缝形成机制和外观变形与微震活动性之间的关系。(5)将岩石微破裂事件与常规变形观测资料、地质资料、施工状态和数值模拟结果等相结合,建立了微震活动性与岩体松弛变形活动性之间的关系,探讨了岩体及其扰动条件下背景应力场积累、释放、转移的基本规律,建立了背景应力场演化与微震活动性的关系,为预测岩质边坡变形发展趋势提供了新的思路。(6)基于能量耗散原理,探索性地提出考虑微震损伤效应的岩体劣化准则,建立了边坡微震监测区域内三维有限元模型,结合微震监测得到的丰富震源信息,分析微震破坏损失能量与岩体力学参数之间的关系,通过提出的岩体劣化准则修正岩体力学参数,反演到三维有限元模型,进行大规模科学计算反馈研究,再现了考虑微震损伤效应的岩质边坡渐进破坏过程,并对边坡稳定性进行了评价分析。更多还原

【Abstract】 Rock slope instability or landslide is one of the three natural disasters, and it endangers the safety of state property and people’s lives seriously. To study prediction of slope instability is a worldwide challenge. So far, a systematic, refined and mature regime of theory and method has not come into existence. Monitoring and forecasting of rock slope instability are always one of the most significant research topics on rock slope engineering, and it also becomes one of the hottest and most difficult subjects in the field of rock mechanics and rock engineering. In recent years, as sustainable development of society and economy and strong demand of the renewable clean energy in China, the development of hydroelectric resources exploitation in Southwestern China renders an accelerating trend. A large number of large-scale hydroelectric projects begin to make prophase preparations, survey and design, or come into operation. Such hydroelectric projects will inevitably confront the stability problems of high steep rock slope. The stability issue of high rock slope has big impact on not only the projects themselves, but also the overall environmental security. Therefore, the stability and its control of high steep rock slopes in the southwest of China becomes one of the key technical problems, which affect and restrict the exploitation of hydroelectric resources and construction of hydroelectric engineering.There is an inevitable connection between rock slope instability and microseismi activity inside the rock slope. The microseismicity occurs as precursor for the instability failure of rock slopes, and the evolution of microcrackings inside the unstable slope is prior to the occurrence of slope surface deformation. On the basis of this academic thought, the seismological theory and geophysical approach are applied and microseismic monitoring system is used to capture abundant microseismic information inside rock mass before the macroscopic instability of rock slope. The method has broken through the mode of traditional surface deformation monitoring mode of rock slope. Then, numerical models of rock slope are set up using finite element method and the stress field and evolution pattern of microcrackings of rock slope instability have been interpreted through large-scale scientific computing. Moreover, the impact of microcrackings evolution, propagation inside rock mass on microseismicity during the failure processes of microstructures was also probed, including tempo-spatial distribution regularity of AE and its precursor mode of rock slope instability during rock mass failure processes. The relation among microseismicity, stress field evolution and construction activities of the rock slope is also discussed. Consequently, the predictive approach of rock slope instability has been established based on microseismic monitoring and numerical simulation. The research results can not only reveal the essence of rock slope instability, but also contribute to understand the formation of instability failure and its occurrence criterions of rock slope. They also provide new ideas and methods for investigating dynamic stability and forecasting instability of rock slopes under complex stress condition. This study possesses significance and provides a guidance role in alleviating or avoiding the instability disasters of rock slopes, and ensuring the safety of construction and operation of the hydroelectric high steep rock slopes. The six aspects of work done in this thesis are listed as follows:(1) The microseismic monitoring system in the left bank slope of Jinping first stage hydropower station is established successfully, and real-time monitoring and analysis of the left bank slope stability and its potential hazardous regions are realized. Through in-depth investigation with geological data, geophysical prospecting information, construction documents and on-site observation, the option of microseismic sensor and optimization design of monitoring system network have been performed according to the requirements of positioning accuracy of seismic source and monitoring sensitivity, engineering specifications and the aim of slope monitoring. The scheme of monitoring system can satisfy the requirements of technical economy.(2) After investigation with different vibration signals of the rock slope, a comprehensive method integrating on-site observation, construction activity information and time-frequency analysis technique has been put forward to study the amplitude-frequency of different vibration waveforms. The waveform characteristics of rock mass microcrackings are thus obtained. Additionally, manual tap tests are used to calibrate the sensitivity and veracity of microseismic sensors. The artificial fixed blasting tests are employed to determine the equivalent whole wave velocity model. The test results show that the positioning accuracy of microseismic monitoring system at the left bank slope of Jinping I hydropower station completely meet the engineering requirements. The main factors influencing seismic source location error are also discussed.(3) The potential failure mechanism and its characteristics, the response regions of construction and consolidation grouting of the left bank slope are investigated on the basis of tempo-spatial distribution regularity of microseismic activities. The damage zones in deep rock mass of the left bank slope induced by construction, excavation and consolidation grouting are identified and delineated. The results can provide some references for excavation, reinforcement measures and conventional monitoring of the rock slope later on. (4) The initiation, propagation, extension, interaction and run-through mechanisms of microcrackings during the progressive failure processes of rock slope are investigated during 2-D,3-D dimensional conditions using Realistic Failure Process Analysis code (RFPA). The spatial evolution regularity of stress field and microseismic activity of the rock slope during progressive failure processes is probed, and the research method using microscopic damage evolution processes revealing macroscopic rock mass structures failure is thus formed. The gestation and occurrence processes of rock slope instability are studied from stress field evolution and tempo-spatial distribution of microseismicity, and the abundant phenomena such as stress buildup, stress shadow and stress transference during the processes of instability catastrophe gestation of rock slope are replayed. Moreover, the stress field of the progressive failure processes of rock slope obtained by numerical modelling and unusual activated information induced by construction disturbance and geological structures such as faults and fissure zones obtained by microseismic monitoring are coupled for analysis. The results reveal the mechanism of tectonic activization and instability catastrophe of rock slope induced by artificial perturbance. Through the coupling analysis of microseismic monitoring and numerical simulation, the practical problems occurred at the left bank slope are dealt with. The formation mechanism of cracks on the platform of the dam and the correlation between surface deformation and microseismicity are interpretated.(5) On the basis of synthesizing microseismicity, traditional deformation observation data, geological information, construction activities and numerical modelling, the correlation between microseismicity and rock mass relaxation deformation activities is established. The basic regularity of accumulation, release and transference of background stress field under rock mass and its disturbance conditions is discussed. In addition, the relation between background stress field evolution and microseismic activity is also established. The comprehensive approach offers a novel idea for predicting the deformation growing trend of rock slope.(6) Rock mass degradation criterion after taking microseismic damage effect into account is put forward exploratively based on energy dissipation principle. The three dimensional FEM model in the region of microseismic monitoring is set up. The relation between dissipation energy of microseismic damage and mechanical parameters of rock mass is analyzed on the basis of abundant seismic source data attained by microseismic monitoring. Then, the suggested rock mass degradation criterion is used to revise the mechanical parameters of rock mass, and the updated data will be input into the 3D FEM model. Feedback analysis of large-scale scientific computing is thus performed. Finally, the progressive failure processes of rock slope considering microseismic damage effect are replayed and evaluation analysis of slope stability is carried out.更多还原