【作者】 胡夏嵩；

【导师】 杜东菊； 赵法锁；

【作者基本信息】 长安大学 ， 地质工程， 2002， 博士

【摘要】 本文立题“低地应力区地下洞室围岩稳定性研究”，主要研究洞室所在区水平方向应力在远小于垂直方向应力时，即水平方向应力处于低水平状态的地应力场条件下，洞室开挖后的围岩稳定性问题。本文结合实际工程，通过野外实地勘测，室内外岩土物理力学性质综合测试、试验以及室内资料综合分析、整理等基础上，结合论文的主题主要进行了以下几个方面的研究：(1)对研究区内地应力场状态进行了定性和定量等两方面的系统分析与论证；(2)系统性研究了研究区工程地质条件，并通过对区域构造格局及演化历史分析，指出了研究区地应力场存在着转化的特点，并论证了其转化的全部过程；(3)对研究区洞室围岩岩体(石)的物理力学性质、围岩岩体质量分级与评价进行了系统研究；(4)对低地应力区洞室围岩岩体结构、围岩工程地质岩组划分进行了研究；(5)通过对研究区洞室围岩变形破坏地质标志和主要影响因素的分析，对低地应力区洞室围岩变形破坏的基本类型、模式以及机理等进行了二维有限元和二维离散元的仿真模拟研究；(6)对低地应力区洞室围岩稳定性的评价方法进行了系统研究；即采用了本文所提出的评价方法选取了若干典型断面进行了稳定性评价，并采用了二维有限元法进行了围岩稳定性的数值模拟与验证，同时，还对低地应力区初始地应力场、洞室开挖后围岩二次应力场以及洞室开挖后围岩变形破坏等诸方面特征进行了系统性研究；(7)对低地应力区洞室围岩的开挖方式以及开挖后相应支护时间的合理确定等进行了研究。通过以上7个方面的研究，本文取得了以下进展和新认识： (1)通过系统研究，作者首次得出了研究区地应力场为低地应力状态的结论；并结合研究区特征，系统性地总结出了地应力状态的划分方法，提出了从定性到定量两个方面对地应力状态进行划分。前者，通过对区域构造格局及其演化过程的研究认为：秦岭上升渭河下降的过程，始于自始新世的近SN向拉张应力作用下进行的，且这种作用至今仍在进行，其结果致使研究区岩体破碎、应力释放，从而有利于形成低地应力状态；其次，对反映地应力状态的有关地质标志进行了系统研究，总结出了能够反映研究区属于低地应力状态的六个方面的地质标志，这些地质标志基本上符合孙广忠教授提出的低地应力区所具有的地质标志。后者，作者提出了以岩石强度应力比为主要方法，兼以地震波速度、地震CT勘探等方法手段综合起来进行评价。 (2)研究区洞室围岩其基本类型由云母石英片岩、绿泥石片岩以及钙质石英岩等三种类型所组成；按成因结构面类型划分为变质结构面、构造结构面和次生结构面等三种类型。同时，首次对上述各种成因类型的结构面相应进行了结构面级序的划分。此外，洞室围岩结构体的形态可划分出五种基本类型，它们分别为楔形结构体、锥形结构体、菱形结构体、方形结构体以及聚合形结构体等，其中，以楔形结构体类型最为发育。 (3)研究区洞室围岩岩体工程地质岩组的划分，除了以岩性和原生结构面作为主要的划分标志以外，结合低地应力区围岩结构特征，作者将次生结构面如卸荷裂隙等也作为其中的划分标志之一，并相应地提出了低地应力区围岩工程地质岩组划分的基本原则和划分依据。据此，将研究区引水洞、溢洪洞等两洞室围岩划分出7个岩组，泄洪洞围岩划分出6个岩组。 低地应力区地下洞室围岩稳定性研究 (4)采用岩体力学介质属性分级方法(即BQ法)对研究区引水洞、溢洪洞以及泄洪洞进口段围岩进行了岩体质量分级与评价。根据围岩岩体质量分级与评价结果，作者认为BQ法属最为适合于低地应力区围岩岩体质量分级与评价的方法之一。 (5)对研究区洞室围岩岩体结构系统研究的结果，可将低地应力区围岩划分出四种结构类型，即块体状结构、层状结构、碎裂结构以及散体结构等类型，其中以后两种结构类型最具代表性。 (6)低地应力区洞室围岩变形破坏存在着宏观、微观等两方面的地质标志，但根据低地应力区围岩变形破坏特点，以宏观地质标志的研究更为重要，如围岩组成、围岩结构、围岩变形破坏监测位移量及岩层产状的变化等四个方面的研究具有重要的意义。 (7)提出了低地应力区洞室围岩变形破坏的三种基本类型，即掉(落)石块型、拱顶塌落型以及侧壁滑落型等;在此基础上，分别论述了各自在物质组成、结构等方面的特征，并确定了其相应的变形破坏模式。根据低地应力区围岩结构特点，采用小范围内，按2一3组结构面切割围岩所形成的三角形、倒三角形以及四边形等块体的变形破坏规律，分别对上述三种类型的形成机制进行了定性分析，同时，相应进行了二维有限元和二维离散元的动态仿真数值模拟。 (8)作者首次提出了低地应力区洞室围岩稳定性的系统评价方法，即该方法系由块体平衡理论、解析法以及多因素综合法等三种基本方法所组成。其中，解析法是由弹塑性围岩洞周最终位移解析解理论和岩体强度理论两种方法所组成，前者，尚属作者首次提出的一种新的评价方法，并建立了弹塑性洞周最终位移解析式，给出了洞周允许最终位移量的计算公式，并确定了其相应的评价方?更多还原

【Abstract】 In this thesis, the author studies surrounding rockmass stability of the underground excavation in the low rock stress region, in which vertical stress is higher than horizontal stress. Accompany with site investigation and site and laboratory tests in the Heine hydroelectric project of xi’an, the author does his study, which consists of six parts: (1)The quantitatively and qualitatively research of rock stress field in the region; (2)Transit process of rock stress field of research region; (3)Physical-mechanical properties research of surrounding rockmass of the region excavations; (4)Surrounding rockmass structure research, including 3 aspects: discontinuity types, discontinuity integration types and intergration relationship between discontinuities and structural blocks; (5)The research of types, models, mechanisms defonnaton and failure of surrounding rockmass; (6)The research of evaluation method of surrounding rockmass stability and corresponding engineering measures. And then, some advances have been made, they are listed as follows:(1) It is the first time to summarizes the division methods of the rock stress field, though taking research region as an example, and directly point out that it is the best way to qualitatively and quantitatively methods. The author uses five kinds of geological symbols put forward by prof.Sun Guangzhong, as the basis for the qualitatively division method, and uses the stress rate of rockmass strength, with references of the seism wave speed and seism CT, as the basis of quantitatively division method. By the new division methods, the example research shows firstly that the research region lies in low rock stress state.(2)The study of the surrounding rockmass and their structures in the diversion, spill and flood excavation reveals that there are three basical surrounding rockmass types, in the region-mica schist, chlorite schist and calcareous quartzite. Three basical surrounding rockmass structural planes have been approved, they are metamorphic, structural and secondary structural planes. Aaccording to discontinuities rank analysis, 12 of 62 faults in the diversion excavation, 12 of 31 in the spill excavation and 23 of 61 faults in the flood excavation, belong to the rank II. The rest of all the faults belong to the III or IV. There are five kinds of the structural blocks around the excavation region: wedge-form, pyramid-form, diamond-form, panel-form and polymerization-form blocks.(3)It is first time to take secondary structural planes, such as unloading fissures, etc. for the one of symbols of engineering geological petrofabric division, and to put forward the basical principles of engineering geological petrofabric division in the low rock stress region. There are7 petrofabrics existence either in the diversion excavation or in the spill excavation, and 6 petrofabrics in the flood excavation.(4)BQ method is suggested as one of favourable ways for evaluation and classification of rockmass quality in the low rock stress region. And the BQ method is used to evaluate and classify the surrounding rockmass in the excavations.(5)There are 4 types of rockmass structure in the research region according to the rockmass structure division scheme set up by the Geology and Geophysical Institute, Academy of China Science. They are block, beded, cataclastic and scattered structures relatively.(6)The study of geological symbols and influential factors on the surrounding rockmass disformation and failure in the section 0+380, shows that measurement and velocity of displacement at the arch of excavation are much more notable than they are sides.(7)On the basis of above research, three basical deformation and failure types of the surrounding rockmass have been summarized, which are falling, arch collapse and side slide types. For each type, its composition, structure and deformation and failure model has been given; its mechanism and process of deformation and failure have been simulated by 2-D FEM and 2-D DEM.(8)It is first time to generize three evaluation sch更多还原