加高重力坝改善坝踵应力及抗滑稳定性的施工措施研究

Research on Construction Measures for Improving Dam Heel Stress and Anti-sliding Stability of Heightened Gravity Dam

大坝加高是实现已建水库扩容增效的主要手段之一,然而原工程相对应的设计标准可能偏低,导致加高后的坝体应力和稳定难以满足设计要求。结合实际工程,运用材料力学理论研究了降低坝踵拉应力的浇筑顺序以及提高坝体抗滑稳定性的新老坝错层浇筑方式,并用有限元软件ABAQUS验证了材料力学法的结论。计算结果表明:分期加高使得老坝坝踵应力恶化,新坝坝踵的竖向拉应力大于一次建坝,对坝踵应力不利。在本工程中,当浇筑至下游侧1/3坝高范围内的混凝土坝块时,会削弱上游坝踵竖向压应力,故该部分混凝土提前浇筑能有效降低坝踵拉应力。采用新老坝错层浇筑的抗滑稳定安全系数比未错层时高2%~5%,优先对加高重力坝前帮错层浇筑能有效提高坝体抗滑稳定性,减少坝体塑性应变。

Dam heightening is one of the main means to realize the capacity expansion and efficiency increase of constructed reservoirs.However,lower design standards of the original project may result in difficulties in meeting the design requirements for the stress and stability of the dam body after heightening.Combined with a actual project,the pouring sequence to reduce the tensile stress of dam heel and the staggered pouring method of the new and old dam body to improve the anti-sliding stability are studied by using the theory of material mechanics,and the conclusions of the material mechanics method are verified by using finite element software ABAQUS.The calculation results show that the staged heightening makes the old dam heel stress deteriorate,and the vertical tensile stress in new dam heel is larger than that of the one-time dam construction,which is unfavorable to dam heel stress.In this project,when the dam concrete block is poured within 1/3 dam height on the downstream side,the vertical compressive stress of the upstream dam heel will be weakened,so early pouring of this part of concrete can effectively reduce the tensile stress of dam heel.The safety factor of anti-sliding stability of the new and old dams with staggered pouring is 2%-5%higher than that without staggered pouring,the preferential use of staggered layer pouring on the front side of the heightened gravity dam can effectively improve the anti-sliding stability of dam body and reduce the plastic strain of dam body.