故县水库混凝土大坝平面有限元计算及安全性评估

Evaluation on Plane Finite Element Calculation and safety of Guxian Concrete Dam

通过有限元计算,对故县工程坝基低弹模岩层修筑混凝土高坝的稳定、应力、变形条件进行分析评价,并探讨深层滑动、摩擦系数、允许变位控制指标值等问题。从计算成果看,故县大坝断面由稳定条件控制,坝体应力满足重力坝规范要求,坝基低弹模岩石应力经点抗滑安全系数法评定,基本满足要求;从应方或变位上看,坝基深层滑动稳定均满足要求。但基础低弹模较软弱Ⅳ类岩体各坝段有少量单元超过允许应力界限,进入塑性应力区,基础应力条件并不富余。因此,从稳定、应力和变位诸条件综合分析,结合较软弱Ⅳ类岩体的具体工程条件,摩擦系数由0.7降到0.57～0.60是合适的,起到了扩大坝底断面的作用,保证了工程的安全。

Through finite element calculation,the paper analyses and evaluates the conditions of stabili-ty,stress and deformation for building a high concrete dam on low elastic modulus rock strata ofGuxian dam foundation.It also discusses the issues of deep slide,friction coefficient and control-ling index for allowable displacement.It is shown by the result of calculation that the dam crosssection is controlled by steady condition,the stress of dam body meets the requirements of gravitydam standard and the low elastic modulus rock stress of the dam foundation basically meets therequirements evaluated by the method of point safety factor against sliding and;from stress or dis-placement points of view,the deep slide stability of the dam foundation can satisfy the demands.Moreover,a few elements in each dam section of type Ⅳ weaker rock mass of the foundation withlow elastic modulus have exceeded the boundary of allowable stress and entered into plastic stresszone.Therefore,it is reasonable to decrease the friction coefficient from 0.7 to 0.57～0.6 accord-ing to the comprehensive analysis of stability,stress and displacement and the specific conditionsof type Ⅳ weaker rock mass.This has played the function of enlarging the cross section of dambottom and ensured the safety of the project.