高水头、大流量作用下反拱水垫塘底板失稳破坏机理研究

Experimental study on failure mechanism of the apron slabs of an inverted arch plunge cushion pool under high water head and large discharge

以国内某一在建高坝工程为参照,对高水头、大流量作用下反拱水垫塘拱圈底板块局部失稳破坏与拱圈整体失稳破坏的机理进行了试验研究。试验考虑了底板锚固失效、止水破坏的极端情况,变量取为水位、流量、底板块缝宽、拱圈可振动的底板块数目、拱端固定与可动的边界条件及其不同组合。研究表明,底板块上举力、运动底板块数目、拱端约束条件、底板缝宽是拱圈失稳的重要因素。拱圈局部破坏是由于拱圈振动底板块数增多,底板缝宽"增加与累加效应",使底板块径向位移增大、轴向约束减小,底板块最终滑出座穴;而拱圈整体破坏则是由于拱座微小位移使拱圈底板失去彼此轴向约束造成。反拱水垫塘运用时,应保持拱座绝对稳定,并控制底板块缝宽,特别是左右缝宽在一定范围。

Experiment was conducted to study the overall and partial failure mechanisms of the apron slabs of an inverted arch plunge pool under high water head and large discharge for the hydraulic design of a high arch dam project under construction.Various factors are tested in this study,such as water head,discharge,the opening of contraction joints between slabs,the number of movable slabs on the arch ring,boundary condition of movable and fixed arch-abutments,and their combinations in the extreme case that all the water seals between slabs are out of function.Results show the three most important factors of great uplift force acting on the apron slabs,constraint conditions on the arch abutments and opening of slab joint.Local instability or slab sliding away from the arch ring is caused by the increasing vibratory displacements of slabs and the decreasing axial restriction between slabs,a result of the widened or accumulatively widened joint openings and the excessive numebr of movable slabs on the ring.The global instability or losing axial restriction of slabs on each other is a consequence of a small displacement of the arch abutment.In a practical design of inverted arch plunge pool,the stability of arch abutments must be totally guaranteed,and the slab joint opening,particularly the right-and-left joints,should be controlled within an appropriate extent.