【作者】 郭涵宇；

【导师】 邓辉；

【作者基本信息】 成都理工大学 ， 地质工程， 2010， 硕士

【摘要】 拟建的西南某水电站坝址位于云南省德钦县澜沧江上游河段上,是云南省境内澜沧江上游水电规划梯级开发的第一级,属龙头水库,上游与位于西藏昌都地区芒康县盐井乡境内的古学梯级水电站衔接,下游接果念梯级水电站。紧邻上坝址上游左岸部位,分布有一大型冰水堆积体,并且下伏基岩存在强烈的倾倒变形,边坡一旦发生整体失稳破坏将会极大的威胁拟建上坝址的安全和电站正常运行的安全。本文以该边坡为研究对象,在对边坡的区域地质背景、工程地质环境条件,以及对冰水堆积体的结构特征、物理力学性质、倾倒变形体的结构特征的研究基础上,对倾倒变形体成因机制进行了分析;然后,通过对坝前边坡在蓄水后的变形破坏机制的研究,并且运用极限平衡法和数值计算的方法对坝前边坡的稳定性进行了分析评价。论文内容和成果主要有以下几点。(1)整个坝前堆积体由分布于基覆界线部位的局部河流相砂卵石层,冰水堆积体,堆积体前缘的河流相砂卵石层三部分组成。冰水堆积体的物质组成以碎块石为主,局部具弱泥质胶结,几乎未见明显架空现象,颗粒之间有一定的定向排列,和一定的成层现象。(2)倾倒变形体的形成和发展大致可以分为以下三个过程:①第一阶段,澜沧江河谷的快速下切使区内应力场产生显著调整,其结果表现为最大主应力为顺坡向的强烈压应力,最小主应力表现为垂直坡向的拉应力。由于应力条件的改变导致岩层向坡外临空方向挤出和向河谷方向倾倒变形。②第二阶段,在上述应力场的作用下使得断层上方岩体向临空方向产生卸荷回弹(由于各层岩体的性质差异,主要表现为差异回弹),岩体结果变得较为破碎,岩体变形存在明显的扩容现象,同时由于F1断层的压缩-倾倒变形的存在,进一步促使上部岩体产生向下的倾倒变形,倾倒过程中产生的巨大弯矩导致岩层根部产生平行坡面的“V”张裂缝。③后期受风化卸荷作用,应力场的再次调整导致F1断层部位进一步产生压缩-倾倒变形,进而使得上部岩体也随之向下进一步倾倒,从而导致“V”型张裂缝进一步扩展,直至形成折断面,最后在折断面部位形成一定范围的塑性破坏区。(4)采用极限平衡法和数值计算的方法对堆积体在各种工况条件下的稳定性分析表明:①天然状态下和持续暴雨条件下,整个坝前堆积体的稳定性良好,无论是局部还是整体其稳定性系数均能满足工程要求;②蓄水前在暴雨+Ⅶ度地震条件下冰水堆积体中前缘稳定性处于极限平衡状态,将可能出现局部的失稳破坏;冰水堆积体整体稳定性较好;③蓄水状态下,坝前堆积体中的冰水堆积体能够保持稳定性状态,但安全储备较低,整体稳定性良好。④蓄水条件下,倾倒变形体的稳定性良好。但由于倾倒变形体内结构面极为发育,岩体结构极为破碎,因此不排除在不利因素影响下产生局部崩塌形式的失稳破坏。⑤蓄水后在考虑Ⅶ度地震条件下,冰水堆积体中前缘很可能发生局部失稳破坏,整体稳定性较好。⑥泄洪条件下,岸坡可能的失稳范围来看,主要限于水位变动带范围内的岸坡岩土体,岸坡出现整体失稳的可能性较小。综上所述,蓄水以前在不考虑Ⅶ度地震的条件下坝前堆积体无论是局部稳定性还是整体稳定性均较好;若考虑发生Ⅶ度以上地震并同时遭遇持续暴雨这种极端条件,冰水堆积体前缘将将可能产生局部失稳破坏,但其整体稳定性较好。蓄水后在不考虑地震条件下坝前堆积体整体上处于稳定状态,但其中的冰水堆积体前缘局部的稳定性安全储备偏低;在考虑Ⅶ度地震条件下坝前堆积体中的冰水堆积体中前缘将可能出现局部失稳破坏,但整体稳定性较好。计算结果表明区内倾倒变形体能够保持稳定状态。更多还原

【Abstract】 A hydropower station in Yunnan province in southwest of China, locats in North West to Foshan LiuTong village on the upstream of Lancang Jiang River.The hydro-power station is the first stage of cascade development of Yunnan Lancang River Hy-dropower planning, which is the leading reservoir, upstream to the GuXue cascade hydropower stations located in the Tibet Qamdo Markam County area, and down-stream to the GuoNian cascade hydropower stations. Close to the upper reaches of left bank of the dam site location, distribution of a large glaciofluvial deposits, and there is strong deformation in underlying bedrock, the failure of the slope will be a great threat to the safety of the proposed dam site and operantion.This paper based on the complex slope closed to a dam in southwest of China as the research object,investgat the back of regional geology, geological environment, as well as the structural features , physical and mechanical properties of glaciofluvial deposits ,the structural characteristics of toppling deformation rock. Research based on the geological origin analysis combined with numerical methods toppling defor-mation formation mechanism is analyzed; and then, analyzing deformation and failure mechanism of the slope in post-storage, and the use of limiting equilibrium methods and numerical calculation methods are analyzed to the stability of the slope. The mainly thesis and the results are as follows.(1) The deposit closed to the dam is composed with fluvial sand and gravel lay-ers on the bedrock layer, glaciofluvial deposits and fluvial sand and gravel layers on glaciofluvial deposits. The glaciofluvial deposit is mainly composed with gravels, in part of which has weakly clay cementation, and there is almost not obvious gap be-tween the gravels, that have a certain orientation, and some layered phenomenon.(2)The formation and development of toppling deformation rock can be divided into the following three processes:①The first phase of the Lancang River valley to the fast incision make regional stress field adjust significantly, resulted as the maximum principal stress along the slope direction that shows a strong compressive stress, and minimum principal stress situating at right angles to the slope direction that shows tensile stress. As the result of rock stress conditions changing, the terrene is squeezed outside direction to the slope and toppling to the direction of the valley with deformation.②In the second stage, the rock on the faultage unloads and rebound with the rock moving towards the direction of outside the slope (due to differences in the character of rock, mainly for the difference in rebound), as a result, the rock mass be-come broken and there is obvious deformation and expansion in the rock mass. Moreover because of the faultage F1 compressing- toppling deformation, the upper rock mass topples downwards furtherly. During the upper rock mass toppling, the roots of rock parallel to the slope generated "V" fissure was the huge moment gener-ated in the process leading to.③In the last stage weathering and unloading leading to the stress field of the faultage F1 readjusted result in further compression-deformation. And thus make the upper rock mass topple down furtherly, resulting in "V" fissure development until the formation of folding cross section. Finally, the part of the scope of the plastic zone form on the folding surface。Using limit equilibrium method and numerical calculation methods accumulation body under different conditions in the stability analysis shows that:①Under the natural state and the conditions of continuous rain, the entire gla-ciofluvial deposits closed to the dam was stable, whether the part o or overall of the stability of glaciofluvial deposits can meet the engineering requirements;②Before the reservoir storage, in front part of the glaciofluvial deposits is going to be failure for the limit equilibrium stability, under the storm +Ⅶseismic conditions, and the stabil-ity of the whole glaciofluvial deposits is better.③I n front part of the glaciofluvial deposits closed to the dam could maintain stability under the post-storage, but the safety coefficient of the glaciofluvial deposits is small, and the stability of the the the whole glaciofluvial deposits is better.The stability of the toppling deformation rock mass can meet requirement under the post storage condition.However, the discon-tinuous surface in the toppling deformation rock mass, of which the structure is not intact, is concentrated. Therefore, it not excluded under the influence of adverse fac- tors in the form of partial collapse of he toppling deformation rock mass.⑤While post-storage, in front part of the glaciofluvial deposits is going to be failure for the limit equilibrium stability, under theⅦseismic conditions,and the stability of the whole glaciofluvial deposits is better.⑥The range of the slope going to be failure limits mainly to the water level changes within the slope, and the slope that will be failure as a whole is less likely to occur.In summary, either the part or the whole of the glaciofluvial deposits closed to the dam is stable, before the reservoir storage, and theⅦseismic load is not consid-ered in the condition;if theⅦseismic load and rainstorm is considered together, in front part of the glaciofluvial deposits is going to be failure in the extreme condition, but the the overall stability could meet the requirement. The whole of the glaciofluvial deposits closed to the dam is stable, under the post storage not considering theⅦseismic load.But the safety coefficient in front part of the glaciofluvial deposits.is not enough.And considered theⅦseismic load, the part of the glaciofluvial deposits closed to the dam is going to be failure, but the whole of the glaciofluvial deposits is stable as well as the toppling deformation rock mass, under the post storage condition.更多还原