【作者】 蔡国军；

【导师】 黄润秋；

【作者基本信息】 成都理工大学 ， 地质工程， 2008， 硕士

【摘要】 澜沧江小湾水电站是我国又一特大型水利水电枢纽工程,最大坝高295m。坝基岩体结构是在建造基础上,经构造改造、浅表生作用以及在开挖卸荷松弛改造作用而逐步形成的。本文在前人研究的基础上,结合一系列的室内试验、大量的野外地质调查、测量和描述,以评价结构面发育机制及其工程地质特征为中心,研究了坝基岩体浅表生改造作用及开挖卸荷松弛特征等,论文取得了以下主要认识:(1)通过一系列室内试验,建立了对坝基岩石强度及变形特性的认识:坝基岩石密度、抗压强度和变形模量都较大,泊松比较小,属于坚硬-极坚硬岩石;其抗拉强度不高;电镜显微下可见晶体发育较多微细的孔洞;坝基岩石受力破坏过程的声发射事件率在不同应力水平的变化很大,开始出现明显声发射的应力量级在6～12Mpa;表明开挖面附近完整岩体初始损伤明显。(2)从微观入手,本文运用扫描电镜(SEM),对坝基岩石在各种受力条件下的岩石破裂断口进行扫描试验,并对现场结构面薄片进行扫描,确定了坝基岩石微观破坏机制分为脆性拉破坏和脆性剪破坏两大类。并得到其典型断口微观形貌图谱。(3)通过现场葱皮现象结构面薄片电镜扫描对比分析,得出其微观断裂机制既有剪破裂(shear failure),也出现了拉破裂特征,且以拉破裂为主,只是部位不同。现场结构面薄片微观形貌对比分析,得出了其呈现出的微观形貌为河流状花样、根状花样等,充分说明缓倾角结构面以脆性拉裂破坏为主体的微观破坏机理。(4)分析了坝基岩体开挖的卸荷松弛现象,包括:沿已有裂隙张开、错动和扩展、葱皮现象、板裂现象、差异回弹和蠕滑以及岩爆现象五种。并根据开挖卸荷松弛程度将小湾坝基岩体分为三个带,即全卸荷松弛带,强卸荷松弛带和弱卸荷松弛带。(5)综合现场调查、物探测试和坝肩槽开挖卸荷松弛数值模拟分析,探讨了小湾坝基岩体的卸荷松弛机理,并阐述了小湾河谷低高程坝基岩体卸荷松弛分带特征。(6)通过大量精细测量和统计分析,确定了拱肩槽及河床部位岩体中缓倾角结构面的特征、发育分布及连通率参数。更多还原

【Abstract】 Xiaowan Hydroelectric Power Station of Lancang River, which arc is 295 meters high, is one of the greatest conservancy and hydropower projects in China. Based on the geotectonic rebuild transformation, the rock mass discontinuities of the dam foundation are gradually formed by the geotectonic rebuilding, the process of epigenetic recreation, and the unloaded and relaxed transformation. This paper combines the massive laboratory experiments with plenty of field geological investigations, the survey and the description on the spot. Taken the genesis and engineering geological characteristics of the rock mass discontinuities as the center, it researches on the base of dam rock mass shallow hypergene transformation process and the unloaded and relaxed characteristics in the excavation. The main achievements are as follows:(1)Through a series of laboratory tests, it has established full developed understanding of the physical mechanics characteristics of the dam foundation rock mass: the density, compressive strength and modulus of deformation are larger, Poisson’s is relatively small, The dam foundation rock mass belongs to hard to extremely hard rock category, its tensile strength is not high. There are lots of small holes in the Crystal Under the Scanning Electron Microscope. The incidence of the AE (the acoustic emission) changes greatly in different stress level during the process of destruction of rock mass. At the beginning of obvious acoustic emission, the magnitude of stress is at the level of 6～12 Mpa. It reveals that the initial damage of the complete rock near the excavation surface is significant.(2) Starting with microscopic, the dissertation uses the scanning electron microscope (SEM) to analyze fractured surface of the dam foundation rock under various stress states and takes the scanning to the samples of discontinuities. It analyzes the microfailure models of the rock mass, which includes tensile failure and shear failure model. It also studies the microfailure mechanisms and obtains the typical fracture morphology maps of the the dam foundation rock mass. (3) By the comparative analysis of mat slice samples of discontinuities, concludes the existing fracture mechanism including shear failure and tensile failure and the tensile failure is the main rupture, just different in locations. The comparative analysis of the morphology of field discontinuities shows that it emerges as the morphology of river-like patterns, root-like pattern, and so on, and the ease dip discontinuities are tensile failure as the main micro-destruction mechanism.(4) analyzes the phenomena of unloading and relaxation, which includes the development along the fissures,the mat slice phenomenon, the board crack phenomenon, the difference rebound and creep and rock burst. the rock mass of dam foundation is divided into three zones by the degree of unloading and relaxation. The three zones are the Completely unloading and relaxation zone, the strong unloading and relaxation zone and the weak unloading and relaxation zone.(5) Integrates the field investigation with analysis of physical prospecting achievements and the numerical simulation of the dam abutment founfation excavation. Discusses the unloaded and relaxed mechanism of rock mass in the dam foundation of Xiaowan hydroelectric power station. And clarifies the zoning characteristics of unloaded and relaxed rock mass in dam foundation at low height of valley.(6) By precise measurements and statistical analyses, it concludes the characteristics distribution and connectivity parameters of the ease dip discontinuities in the dam abutment founfation and the bed river dam foundation.更多还原