牙根二级水电站坝基岩体渗流及其对抗滑稳定性影响研究

发布时间：2019-07-01 10:26

【摘要】：拟建牙根二级水电站位于四川省甘孜州雅江县境内的雅砻江干流上，是雅砻江中游规划的第三个梯级电站，设计为混凝土重力坝，最大坝高153m，相应库容2.54亿m3，装机容量990MW。坝基花岗岩体断裂裂隙发育，在库水头的作用下可能出现因坝基渗流而导致水库渗漏以及坝基岩体失稳的问题。因此，研究坝基渗流问题具有重要的工程实用价值。本文在分析坝址区结构面发育规律的基础上，详细分析了坝基平硐和钻孔结构面资料，建立坝基渗流分析的地质概化模型；根据钻孔压水试验和裂隙统计资料综合确定坝基岩体不同部位的渗透系数；利用Visual MODFLOW软件分别对天然状态和蓄水后坝基三维渗流场特征进行模拟；分析渗流对岩体力学性质的影响，利用FLAC3D软件模拟蓄水后渗流对坝基抗滑稳定性的影响。取得了如下主要成果：（1）总结分析了坝基岩体结构面的发育规律，尤其对缓倾角结构面的发育规律进行了重点研究，得出产状为N40~50°W/NE∠20~25°的缓倾角结构面发育具有绝对优势，其产状稳定、平直、延伸长大，，为构造结构面。根据平硐及钻孔资料分析确定该组缓倾角断裂在坝基岩体中共发育11条，其近似等间距发育，与陡倾角断裂相互切割，构成了坝基岩体渗流及抗滑稳定的基本地质模型。（2）将坝基岩体的渗透结构划分为散体状渗透结构、带状渗透结构及网络状渗透结构三种，其中后两种渗透结构对坝基岩体渗流其主要控制性作用。带状渗透结构主要由断层及其影响带组成，为坝基岩体渗流的主要通道；网络状渗透结构主要由岩体内的各种裂隙组成，为坝基岩体渗流的次级通道。（3）通过钻孔压水试验和渗透系数张量计算，得到坝基岩体的渗透性随深度的增加而递减，新鲜岩体内断层对岩体渗透性的增加作用不明显，岩体渗透性主要随卸荷分带变化。将两种方法进行相互结合，综合选取坝基岩体的渗透系数。（4）水库蓄水后，两岸山体内地下水位线呈现先增高后逐渐降低的变化趋势，蓄水五年后地下水位降低速度放缓，水位线趋于稳定；重力坝的设置使两岸山体出现了一定的绕坝渗流现象，右岸绕坝渗流现象明显大于左岸；设置防渗帷幕后，渗流场向深部延伸，渗漏量降低；坝基岩体渗漏量较小，防渗帷幕能起到较好的防渗作用。（5）坝基岩体发育不利于其抗滑稳定的结构面组合；地下水通过潜蚀结构面性状、劈裂结构面宽度、降低岩体围压使岩体的力学性质发生损伤；在不设抗剪齿槽的情况下，蓄水后重力坝会沿fh07和fh09发生2mm的错动，剪应变贯通，稳定性较差；设置抗剪齿槽后能有效控制fh07和fh09的错动，使岩体的稳定性增加。
[Abstract]:The proposed root-level hydropower station is located on the main stream of the Yamen River in Yajiang County, Ganzi Prefecture, Sichuan Province. It is the third step power station planned in the middle reaches of the Yamen River. It is designed as a concrete gravity dam. The maximum dam height is 153m, the corresponding storage capacity is 2.54 billion m3, and the installed capacity is 990MW. The fracture and fracture development of the granite body at the dam foundation may cause the seepage of the reservoir and the instability of the rock mass of the dam foundation due to the seepage of the dam foundation under the effect of the reservoir head. Therefore, it is of great practical value to study the seepage of dam foundation. Based on the analysis of the development of the structure surface of the dam site, this paper analyzes the data of the dam foundation and the surface of the drilling structure in detail, and establishes the geological model of the seepage analysis of the dam foundation. The penetration system of different parts of the dam foundation rock mass is determined according to the drilling water pressure test and the fracture statistics. The characteristics of the three-dimensional seepage field of the dam foundation after water storage are simulated by using Visual MODFLOW software, and the effect of the seepage on the mechanical properties of the rock mass is analyzed, and the anti-sliding stability of the dam foundation is simulated by using the FLAC3D software. In response. The following master has been obtained The results are as follows: (1) The development law of the structural surface of the rock mass of the dam foundation is analyzed and the development law of the surface of the gentle dip angle structure is studied, and the development of the slow-dip structure with the occurrence of N40-50 掳 W/ NE and 20-25 掳 has an absolute advantage. Its occurrence is stable, straight, extended, The structure surface is constructed. According to the analysis of the level and the drilling data, it is determined that the set of gentle dip faults have a total development of 11 in the dam foundation rock mass, the approximate equal-spacing development, and the steep dip angle fracture are mutually cut, so as to form the basis for seepage and anti-sliding stability of the rock mass of the dam foundation and (2) dividing the permeable structure of the dam foundation rock mass into three types of an aqueous dispersion-shaped permeable structure, a strip-shaped permeable structure and a network-shaped permeable structure, wherein the following two permeable structures are used for seepage of the rock mass of the dam foundation The main control effect is that the belt-like penetration structure is mainly composed of the fault and its influence belt, which is the main channel for seepage of the rock mass of the dam foundation; the network-like penetration structure is mainly composed of various fractures in the rock mass, which is the rock mass of the dam foundation (3) The permeability of the rock mass of the dam foundation is decreased with the increase of the depth, and the permeability of the rock mass is not obvious, the permeability of the rock mass is not obvious, and the permeability of the rock mass is not obvious. The two methods are combined with each other, and the comprehensive selection The permeability coefficient of the rock mass of the dam foundation. (4) After the reservoir is impounded, the water table line in the mountain body of both sides of the cross-strait is gradually reduced after the water storage is increased, and the water level decreases after the water storage for five years, and the water level line is stable; and the setting of the gravity dam is to make the mountain of both banks The seepage of the surrounding dam on the right bank is obviously larger than that of the left bank. After the anti-seepage curtain is set, the seepage field is extended to the deep part, and the leakage is reduced; and the leakage of the rock mass of the dam foundation is small, and the seepage resistance is low. (5) The development of the rock mass of the dam foundation is not conducive to the combination of the anti-slip and stable structure surfaces, and the mechanical properties of the rock mass can be damaged by the surface property of the submerged structure, the width of the splitting structure, and the confining pressure of the rock mass. In case of no anti-shear tooth slot, the gravity dam after water storage will be 2 mm in the fh07 and fh09, and the shear strain can pass through and the stability is poor; and the fh07 and fh09 can be effectively controlled after the shear tooth slot is set.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV223.4

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