【作者】 李勇；

【导师】 朱维申；

【作者基本信息】 山东大学 ， 工程力学， 2009， 博士

【摘要】 为了鼓励科技创新,中国政府制定的中长期科技发展计划指出:要重点发展基础科学和前沿科技方面的研究,优先考虑能源、水资源和环境保护等领域。而对于能源和水资源的开发,具体就体现在中国西南地区正在兴建和即将要兴建的几十座世界级的大型水电工程。这些水电工程的发电系统大多采用深埋的大型地下洞室群结构,且地下洞室群工程大多处于高山峡谷的环境条件中。洞址经常处于初始高地应力场之中且地应力场受到地形和山体坡度的强烈影响。在此条件下围岩的脆性破裂现象（如边墙的劈裂裂缝、岩爆等工程事故）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陡倾角的脆性劈裂带或大裂缝,如渔子溪、二滩、拉西瓦以及瀑布沟等工程在母线洞都发现了类似的情况,因此对研究复杂条件下的地下洞群分步开挖过程中的稳定性尤为重要。其次,这些地下洞室群的长期稳定性研究也越来越受到重视,因为许多工程的变形与失稳破坏并不是瞬间就发生的,岩体的流变现象处处可见,如地层在地应力的长期作用下发生蠕滑、断裂,洞室群围岩随时间发生长期变形,有的甚至坍塌、破坏或岩层失稳,岩梁、岩板、岩柱屈曲失稳等。本文将以西部正在建设的两个典型的地下洞室群为研究背景,通过实验室试验,大型地质力学模型试验,数值模拟和理论创新,研究了复杂条件下大型地下洞室群的分步开挖稳定性及流变效应,本文的主要研究内容如下:（1）单轴瞬时力学特性试验及压缩蠕变试验——首先通过山东大学岩土与结构中心自行研制的三轴伺服试验机对从工程现场所取的典型的硬岩（花岗岩和大理岩）进行了单轴压缩瞬时力学特性试验研究,分析了硬岩的全应力—应变曲线的各个阶段及岩样的变形特征、强度特征和破坏规律,得到了硬岩的的基本力学参数,为下一步进行硬岩的蠕变试验和数值计算提供依据。在研究硬岩的单轴压缩蠕变过程中,研制了一套单轴压缩蠕变装置,通过该装置对锦屏一级地下洞群附近所取的大理岩进行了单轴压缩蠕变试验研究（包括干燥试件和饱水试件）,得到了各试件在不同应力水平下的单轴压缩蠕变曲线,特别观察了实验过程中泊松比的变化规律,并在Nishihara模型下进行了模型参数的反演分析,为下一步进行锦屏一级地下洞群的长期稳定性研究提供试验依据。（2）新型岩土相似材料的研制——在进行大型地质力学模型试验之前,必须找到一种相似材料来模拟工程岩体。本文在调研了大量国内外相似材料的基础上,研制出了一种由铁精粉、重晶石粉、石英砂、石膏粉及松香酒精溶液混合压制而成的新型（IBSCM）岩土相似材料。通过实验室的单轴抗压强度试验、假三轴试验、巴西试验等经典力学试验研究了这种新型岩土相似材料在不同配比条件下的力学特性,并成功用于多个大型地质力学模型试验中,其中包括本文所研究的大型地下洞群稳定性地质力学模型试验。（3）大型地下洞群分步开挖稳定性研究——在进行大型地下洞群分步开挖稳定性的研究中,以大渡河流域双江口电站地下洞群为研究背景,开展了准三维大型地质力学模型试验和数值模拟研究。研制了一套具有自主知识产权的用于地下洞群稳定性研究的三维钢结构模型试验台架,并配备了全自动的液压加载系统,在台架的前后（洞室部位）设置了透明的钢化玻璃观察窗,可观察模型表面在加载过程中的裂纹扩展情况。在整个试验的测试过程中,首次将多种先进的变形测试技术用于监测围岩变形,实现了洞室群模型开挖过程中的高精度的实时测量。在锚固模拟技术中,研制了可施加预应力的微型模型锚索以及发明了埋设注浆锚杆的独特锚固技术。通过模型的超载试验,观测了洞室群围岩从产生微裂纹、起裂、扩展直至产生较大范围劈裂破坏的整个变形破坏过程,并深入研究了劈裂破坏中产生的张开位移。同时对开挖过程和超载过程进行了FLAC^3D数值模拟,试验测试结果、数值模拟结果和理论推导结果都进行了对比分析,分析结果对实际工程的施工过程和今后的试验工作起到了一定的指导作用。（4）大型地下洞群长期稳定性研究——在研究地下洞群的长期稳定性研究中,基于现场的节理岩体的地质资料及实验室单轴压缩蠕变的试验结果,建立了节理岩体的非定常损伤流变模型。首先引入一个二阶的损伤张量来描述节理岩体的几何初始损伤,其中,节理面的面积、方向、间距和密度作为影响损伤张量的主要因素;其次,以Nishihara模型作为描述岩体时效特性的基本模型,并通过对应原理将一维形式的Nishihara模型推广到三维形式:然后应用等效应变假设,将二阶的损伤张量引入到流变本构方程中;紧接着用单轴压缩蠕变试验得到的相关流变参数的非线性表达式应用到流变本构方程中;在VC++7.0的环境下,以FLAC^3DVersion 3.0有限差分软件为开发平台,编写了上述本构关系的程序块,实现了节理岩体非定常损伤本构模型的二次开发。最后将此模型同时应用于研究四川大渡河流域双江口地下洞群和四川雅砻江流域的锦屏一级电站地下洞群的长期稳定性研究中,预测了复杂条件下大型地下洞群的长期稳定性,并与弹塑性计算的作了对比分析,为大型地下洞群的长期稳定和安全性提供了合理的评价和建议。更多还原

【Abstract】 To encourage scientific innovation,the Chinese government has formulated a Mid- to Long-Term Plan for Development of Science and Technology（2006-2020）,which highlights research in the basic science and frontier technologies,with priority given to energy,water resources and environmental protection.As for the exploitation of energy and water resources,it is concretely embodied in the several dozens of world-class hydroelectric power stations in southwestern areas of China.The underground cavern groups are mostly adopted in these projects.Moreover,these underground caverns are generally located in the high mountain-canyon areas which give rise to high in-situ stresses in vicinity of the underground cavern groups.The high in-situ stresses are also intensely influenced by the terrains and slope gradients. Under the complicated circumstances,splitting or spalling failures just like falling masses and rockburst frequently appear in the construction process,especially near the side walls of underground caverns in the actual projects just like Yuzixi Hydropower Station,Ertan Hydropower Station,Laxiwa Hydropower Station and Pubugou Hydropower Station.Therefore,it is very significant and necessary to study the stability of surrounding rock masses in the process of stepped excavations. Secondly,the long-term stability of underground cavern groups is also highlighted since the deformation and crippling failures in most projects are not completed in a short time.The rheological phenomena can be found everywhere,for instance, sliding,cracking,even collapse and other failures often occur in the rock masses due to the long-term action of high in-situ stress.In this dissertation,taking two underground cavern groups which are under construction as the engineering background,the laboratory experiments,large-scale geomechanical model test, numerical simulations and theory innovations are comprehensively applied to study the stepped-excavation and long-term stability.In this dissertation,the main investigation work focuses on the following.（1） Using the servo-controlled testing machine developed by Geotechnical & Structural Engineering Research Center of Shandong University,uniaxial compressive experiments are performed on the granite and marble specimens.Each stage of the complete stress-strain curve,deformation characteristics,strength characteristics and failure principles are analyzed.The physico-mechanical parameters of rock masses are also obtained,which provide the accurate parameters for the rheological tests and numerical simulations.During the study on the uniaxial compressive rheological tests of marble specimens,a newly apparatus is developed and the uniaxial compressive rheological tests are performed（including a dry specimen and a water-saturated specimen）.The relationship curves between axial/circumferential strain and stress levels are obtained,and therefore the variation curves of Poisson’s ratio are also obtained.According to the curves,the related rheological parameters are also obtained through inversion analyses on a basis of Nishihara model,which can provide the accurate parameters for long-term stability analyses of the actual projects.（2） Prior to the large-scale geomechanical model test,a newly developed analogous material is developed to simulate most rock masses.After conducting literature reviews on the analogous materials all over the world,a new analogous material called IBSCM is developed.This is made from iron mineral powder,barite powder,quartz powder and alcoholic solution with rosin.Some tests such as uniaxial compressive test,quasi triaxial test and Brazilian test have been performed to obtain the physico-mechanical parameters of the composite material under different proportional mixtures.IBSCM has been successfully applied in several large-scale geomechanical model tests including the one which will be introduced in this dissertation.（3） In the study on the stability of stepped excavation,taking the underground cavern group of Shuangjiangkou（SJK） Hydropower Station as an engineering background,a large-scale quasi-three geomechanical model test and numerical simulations are performed.The developed steel structure can simulate the complicated circumstances just like high in-situ stress and high overburden depth.It also can apply the true 3D loading on six surfaces of the physical model.An automatic hydraulic loading system is also developed.Transparent windows are installed in the steel frame to monitor the cracking extension on the model surfaces. During the whole physical model test,a few advanced deformation monitoring techniques are applied together firstly,which realize the accurate real-time monitoring in the process of excavations.A unique grouting technique and prestressed cables are adopted in the model test.Through the overloading test,the whole process from micro cracks,crack initiation,crack extension to wide-range failures is monitored.The opening displacements induced by splitting failures are further studied through a proposed displacement prediction formula.The results of test,numerical simulation and theoretical derivation are comparatively analyzed and some principles are obtained,which have made certain guiding significance to the actual projects and future geomechanical model test.（4） In the study on the long-term stability of underground cavern groups,a non-constant-parameter damage rheological constitutive model for jointed rock masses is put forward based on the in-situ geological data and uniaxial compressive rheological test results.In this constitutive model,a second-order damage tensor is applied to describe the initial geometry damage of jointed rock masses,thereinto the major influencing factors are joint plane areas,directions,spacing and density.Then, taking the Nishihara model as the basic model to study the time-dependent characteristics of rock masses,its one-dimensional constitutive equations are transformed into three-dimensional forms.The three-dimensional visco-elastic-plastic damage constitutive equations are deduced by introducing the second-order damage tensor into the rheological constitutive equations on a basis of the equivalent strain hypothesis.Next,the related parameters are substituted by the nonlinear expressions of the rheological parameters obtained from the uniaxial compressive rheological tests.Eventually,taking FLAC^3D Version 3.0 as the development platform,the non-constant-parameter damage rheological constitutive model for jointed rock masses are compiled in the environment of VC++7.0,which realize the secondary development of FLAC^3D.Experimental results and this new constitutive model are applied to the engineering practice of rock mass engineering in the study on long-term stability of underground cavern groups in SJK Hydropower Station and Jinping First Stage Hydropower Station.The long-term stability of rock engineering under complicated circumstances is predicted and compared with the elasto-plastic analyses,which brings forward reasonable evaluation and suggestion for long-term stability and safety of rock engineering.更多还原