【作者】 刘维国；

【导师】 沈军辉； 李天斌；

【作者基本信息】 成都理工大学 ， 岩土工程， 2009， 硕士

【摘要】 牙根水电站位于四川省甘孜州雅江县境内的雅砻江干流上,是雅砻江中游规划第二个梯级电站。预可行性阶段勘探揭露坝址区右岸坝前Ⅰ～Ⅴ勘探线一带发育顺河流长约850m,方量约800万方的拉裂松动岩体,表现为不仅顺河裂隙普遍张开,且横河向裂隙也具拉裂变形。查明拉裂松动岩体的边界条件、分布范围、变形破裂特征,分析其成因机制及破坏模式,对预测其在水库正常蓄水后各工况下的稳定性,进而评价其对牙根水电站的影响具有重要意义,同时对高地应力深切峡谷斜坡岩体的变形破坏机制研究具有一定的理论意义。本文深入系统地研究了拉裂松动岩体边坡的岩体结构、变形破裂特征及其赋存的地质环境条件,分析建立了边坡岩体变形破坏的地质力学模式。在此基础上采用岩体结构控制论理论,结合研究区区域地质条件、河谷地貌演化史及花岗岩在卸荷状态下的变形破裂性质,从地质地貌演化角度,综合分析了拉裂松动岩体的成因机制,建立了拉裂松动岩体形成演化机制模式;并运用FLAC3D三维有限差分软件,通过模拟研究区河谷地貌演化过程,再现了拉裂松动岩体的形成演化过程,进而评价了拉裂松动岩体的岩体结构控制效应。具体内容及成果如下:(1)根据研究区区域构造背景、区域地貌及新构造活动,分析了研究区应力场产生的区域背景条件,结合区域应力场及地震震源机制解,得出研究区处于NWW～EW向水平主压应力为主的现代构造应力场中。坝址区实测地应力资料显示,河谷斜坡地应力场最大主应力σ1方向为NEE向,与河谷垂直,倾坡外;垂直埋深122m处的σ1量值已达17.7Mpa,属高构造应力区。(2)对研究区花岗岩的岩体结构特征做了系统调研,分级研究了断裂裂隙发育分布、性状特征及其演化特征。得出坝址区断裂裂隙的发育具有明显的空间差异性,据此对坝址区边坡作了结构分区,其中1号拉裂松动岩体所在部位边坡以发育N40-60°W/SW∠60-75°断层(Ⅲ1级结构面)为特征,边坡岩体总体为陡倾坡内逆向板状结构;并根据缓倾角结构面的发育特征,细分为两个亚区,其中YI-1亚区以发育顺坡缓倾角断层为特征,YI-2亚区以发育缓倾角裂隙为特征。(3)根据边坡变形破裂及岩体拉裂松动特征、地震CT测试成果,结合边坡岩体结构,分析确定了拉裂松动岩体的分布范围及边界条件,分析了拉裂松动岩体(Ⅴ2类)的工程地质性质。(4)根据边坡岩体的变形破裂特征,结合岩体结构及河谷地貌演化史分析,建立了边坡岩体变形破坏及拉裂松动的七种地质力学模式:①夷平剥蚀过程沿缓倾角结构面的逆冲剪胀;②倾倒弯曲拉裂变形;③缓倾角结构面差异回弹错动;④岩体板裂化及剪张破裂;⑤中陡倾角结构面的离面卸荷拉裂;⑥滑移剪张;⑦蠕滑拉裂及滑移压致拉裂。(5)围绕花岗岩的岩体力学特性、谷坡岩体结构特征、高地应力背景条件和河谷地貌演化特征,从岩体结构控制论及地质地貌演化角度,分析了拉裂松动岩体的成因。1号拉裂松动岩体是处于高地应力条件下,具有特殊岩体结构的花岗岩体,在河谷形成演化的剥蚀卸荷过程,随着高地应力的释放、谷坡应力场的调整,而发生受岩体结构控制的变形破裂改造的结果,并建立了拉裂松动岩体两个典型成因模式图。(6)概化选取YI-1区河谷底部的顺坡缓倾角断层(f01-6、f01-1-7和f03-17)和拔河100m高程的顺坡缓倾角断层f03-17,F2、F3、F5三条陡倾坡内断层及F8侧向控制断层为谷坡的先成岩体结构,采用FLAC3D三维有限差分软件,施加构造作用力,对研究区河谷地貌演化分五步开挖进行模拟,再现了拉裂松动岩体的形成演化过程。(7)从受到岩体结构效应控制的稳定性和工程开挖处理措施入手,对拉裂松动岩体岩体结构控制效应进行地质综合评价。更多还原

【Abstract】 Yagen hydropower station is located in the main stream of the Yalong river, Which is the second cascade hydropower stations in the middle reaches. The explorations of Pre-feasibility stage showed that there are Ripping loose rock mass between I and V exploration lines in the front of the dam, it is about 850m along the river and is 808 million cubic meters. There is apparent deformation and failure along the crannies. Surveying its border, distribution and deformation and fracture characteristics, and analyzing its genetic mechanism and the deformation and failure mode, is significant to forecast its stability of every condition in water storage and evaluate the influence to Yagen hydropower station. The paper is meaningful to study the deformation and failure mode of deep canyon in high stress field.The paper worked on the rock structure and deformation and fracture characteristics, also the geo-environmental conditions of ripping loose rock mass thoroughly, to find out its deformation and failure mode of geomechanics. Combined with the regional geological conditions, evolution history of valley landforms and deformation and fracture characteristics of granite in unloading state, the paper analyzed the genetic mechanism and constituted the formation and evolution mechanisms of ripping loose rock mass. The paper used Numerical simulation of finite element to reproduce the process of ripping loose rock mass. Then, the paper evaluated the control effect of rock mass structure of ripping loose rock mass. Details and results are as follows:(1) Based on regional tectonic setting, regional landforms and new formation activity, the paper analyzed the region background conditions giving birth to high stress. Combined of regional stress field and earthquake focal mechanism, the paper founded that the study is in the stress field (NWW～EW) now. Information of surveying stress of dam site showed that Contour of SMin is Vertical towards valley(NEE), the value is 17.7Mpa in the vertical depth of 122m. So, the study area is of high tectonic stress.(2) The paper did systematical research to granite rock structure of study area, and studied the faults and crannies in detail, to find the space diversity and make the structure of district. 1# ripping loose rock mass slope is characterized by faults(N40-60°W/SW∠60-75°), and the slope is plate structure dumping within steep slope. Based on the development features of low-angle structure, 1# ripping loose rock mass slope was divided into two subregions, because YI-1 subregion growed low-angle faults and YI-2 subregion growed low-angle crannies.(3) Based on the deformation and failure characteristics, ripping loose characteristics and test results of Seismic CT, combined of rock mass structure of slope, the paper determined the distribution and boundary of ripping loose rock mass, and analyzed its nature of engineering geology.(4) Based on the deformation and fracture characteristics, combined of rock mass structure and evolution history of Valley landforms, the paper put forwarded 7 kinds of deformation and failure modes: :①thrust-shear dilatation along low-angle structures ;②toppling deformation;③Different rebound along low-angle structures;④Board cracking of the intact rock;⑤Relief cracking along middle-steep-structure;⑥Slippage-cut-crack;⑦Squirm-slipping and slipping-pressed-crack;(5) Through study of granite’s mechanical properties, rock mass structure of slope, high stress field and characteristics of valley landforms, from the angle of control of rock mass structure and evolution of valley landforms, the paper analyzed the causes of ripping loose rock mass. 1# ripping loose rock mass is special granite rock mass under high geo-stress, and its was formed by transformation of deformation and fracture, accompanying relief process, release and adjustment of high stress. Then, the paper established two model of typical causes of ripping loose rock mass.(6) The paper selected low-angle faults (f01-6、f01-1-7 and f03-17), steep-inner faults (F2、F3、F5) and lateral control fault (F8), to establish ancestor slope structure. Imposing structure stress, the paper used Numerical simulation (FLAC3D) of finite element to reproduce the formation of ripping loose rock mass by 5 steps.(7) Based on the stability controlled by rock mass structure and engineering excavation measures, the paper evaluated structure effect of ripping loose rock mass comprehensively.更多还原