拱坝沿建基面抗滑稳定的体安全系数及其工程应用

对于坝基岩体发育有顺坡向结构面等复杂地质条件的拱坝,通常需要核算大坝沿建基面单滑面或多个平面组成的复合滑裂面的抗滑稳定性,但目前尚无为工程界公认的计算方法,现行拱坝设计规范也未作出明确规定。本文采用非线性有限元与传统的刚体极限平衡法相结合的分析方法,将滑裂面、坝基面、临空面与结构面相互切割、组合形成的潜在滑体作为研究对象,以坝基岩体内部发育的陡倾角结构面为分界面,将滑体离散为多个按串联或并联方式排列的块体,利用各块体的静力平衡条件与相邻块体间的变形协调条件,分析滑体在拱推力等外力作用下的抗滑稳定安全系数,即体安全系数。结合小湾拱坝工程,开展大坝沿坝基岩体发育的浅层卸荷裂隙抗滑稳定性的分析计算,通过实例分析表明本文方法的合理性与工程实用性。

Body safety factor of anti-sliding stability along the dam-foundation surface of arch dams and its engineering application

For high arch dams with complex geological conditions, such as the dam foundation rock developing with a slope-oriented structural plane, it is necessary to evaluate the stability against sliding along single slip surface or composite slip surface composed of multiple planes. However, there is no calculation method recognized by the engineering at present and no clear stipulation in the current design specification for concrete arch dams. In this paper,the nonlinear FEM and the traditional LEM are used,and the potential sliding mass formed by mutual cutting and combination of slip surface, dam-foundation interface, free surface and lateral cut plane is taken as the research object. Taking the steep joints developed in the rock mass of dam foundation as the interfaces, the sliding mass is divided into multiple blocks arranged in series or in parallel. Based on the static equilibrium condition of each block and deformation compatibility condition between adjacent blocks,the body factor of safety,that is the anti-sliding stability factor of safety of sliding mass under the action of arch thrust, is calculated. The method proposed in this paper is applied in Xiaowan high arch dam to analyze the stability along the shallow unloading fracture surfaces developed in the rock mass of dam foundation. The practical application shows the validity and engineering practicability of the method proposed in this paper.