【作者】 白俊光；

【导师】 曹楚生； 练继建；

【作者基本信息】 天津大学 ， 水利水电工程， 2009， 博士

【摘要】 本论文围绕高地应力地区峡谷高坝坝基开挖扰动效应与河床坝基反弧形开挖形式优化问题,以拉西瓦高拱坝坝基开挖设计为应用背景,就高地应力峡谷区复杂地应力场的非线性反演方法、坝基开挖扰动与锚固支护效应、坝基反弧形开挖形式设计优化以及坝基岩体工程力学性状等方面开展了系统研究,并将研究成果应用于工程设计方案。主要内容包括:(1)在对目前几种典型地应力反演方法进行综合分析的基础上,根据“反演正算”原理,基于地应力实测数据的统计分析和确定性数值计算方法,考虑地应力随埋深的非线性分布特征和岩体非线性力学特性,通过综合集成神经网络的自学习功能和遗传算法的全局寻优能力,首先研究并提出了一种高地应力峡谷区复杂地应力场的非线性反演方法;进而以实测资料为依托,开展了拉西瓦工程地应力场的非线性反演,分析了高地应力峡谷区地应力场的分布特征与形成机理。(2)在上述地应力非线性反演结果基础上,通过详细仿真,模拟坝基开挖步序与锚固支护等施工过程,对拉西瓦高地应力峡谷坝基开挖扰动问题开展了深入研究,根据拉西瓦工程坝基岩石真三轴试验结果提出了拉西瓦工程坝基开挖破坏区的确定方法;通过多方案对比分析获得了高地应力峡谷坝基开挖后的应力、变形与屈服破坏等开挖扰动特征;揭示了锚固措施对坝基开挖扰动应力、变形及屈服破坏的加固支护效应;讨论并提出了关于高地应力峡谷坝基开挖扰动与锚固效应的若干重要结论。(3)根据拉西瓦拱坝坝基的地质条件和高地应力环境,确定了拉西瓦高拱坝建基面高程;针对高地应力区狭窄河谷而提出的。首次提出了对高地应力峡谷坝基采用反弧形开挖形式的设计优化理念;进而采用平面和三维非线性有限元方法,针对新提出的反弧形开挖形式和常规的平底开挖形式的卸荷变形、应力分布特征、岩体强度安全度屈服破坏范围以及坝体应力状况等开展了全面的比较研究,论证了拉西瓦坝基采用反弧形开挖形式的合理性和先进性。(4)采用物探手段以及钻孔摄像等多种手段,对施工过程中拉西瓦河床坝基岩体工程性状开展了现场综合测试,实测确定了拉西瓦坝基岩体在开挖锚固下的卸荷松弛带厚度,验证了反弧形开挖与分步开挖锚固能较好解决高地应力峡谷坝基开挖卸荷问题,可更好地适应和满足高地应力峡谷坝基施工与建设的安全要求,从而表明了本文对拉西瓦坝基开挖扰动效应研究以及反弧形开挖形式优化设计的技术思路是成功的。本文的研究成果对类似高地应力峡谷坝基工程具有良好的应用推广价值。更多还原

【Abstract】 Focusing on the Excavation Disturbed Zone (EDZ) and the optimizing ogee excavation scheme of High-geostress Dam Foundation at deep valley region, a new nonlinear back analysis method of geostress field of high-stress valley region, the excavation disturbing and anchoring effects of high-stress dam foundation, the optimization design of ogee excavation scheme, as well as the mechanical properties of the dam foundation rock masses are systematically studied. The results are comprehensively applied to the safety assessment and design optimization of Laxiwa dam foundation on Yellow River. The following contents are included in this thesis: (1) According to the back analysis idea using forward calculation, a new nonlinear back analysis of geostress field is developed based on the integration of numerical computation, artificial neural network (ANN) and genetic algorithm (GA), in which both the nonlinear distribution characteristics of geostress with burial depth and the nonlinear mechanical behavior of rock mass are taken into account. Moreover, the new nonlinear back analysis method is applied to the engineering background of Laxiwa hydropower project located on the upper reach of Yellow River. (2) Based on the results of geostress field and a detailed numerical simulation of excavation and anchoring processes, the excavation disturbing and anchoring effects of high-stress dam foundation of Laxiwa hydropower engineering are systematically studied. The excavation disturbing characteristics of stress, deformation, yielding and failure zones of the dam foundation are derived. The method of determining the failure zone is provided according to the results of true triaxial tests on granite in the dam foundation. The reinforcing effects on the aspects of stress, deformation, yielding and failure zones of the dam foundation are revealed. Furthermore, the excavation disturbing and anchoring problems of the high-stress dam foundation are profoundly discussed and a series of important conclusions are drawn. (3) The elevation of foundation boundary of Laxiwa dam is determined based on the analysis of geological conditions and high geostress. Through the comparison of ogee excavation scheme andflat-bottom excavation scheme, at the first time, the optimization design of ogee excavation scheme is provided for the high-stress arch dam foundation. Then, the unloading deformations, stress distributions, and safety factors of dam foundation and the stress distribution characteristics of the dam body under the different excavation schemes are computed and analysed, using 2D and 3D FEM, respectively. And thereby, the rationality of ogee excavation scheme is verified for the high-stress dam foundation. (4) A large-scale comprehensive tests on the engineering and mechanical properties of dam foundation rock masses are conducted, using seismic reflection method, sonic method and borehole photography, etc. the depths of relaxation zone of dam foundation due to excavation are determined. The results demonstrate that the problems induced by excavation of high-stress dam foundation can be solved by the combination of ogee excavation scheme, step-by-step excavation and reinforcement. The achievements presented in this thesis can be expanded into the other similar dam foundation engineering at high-stress valley region.更多还原