水垫塘反拱形底板局部稳性分析

A Study on Local Stability of Counter-Arched Slab in Plunge Pool

针对局部脉动随机荷载在某一时刻出现大的数值造成局部板块失稳的可能性,结合某高拱坝水垫塘反拱形底板稳定性的研究,用"随机拱"的概念,建立了基于板块极限失稳的力学模型和与其相应的物理模型,分析了单个板块的局部稳定性,导出了板块局部失稳极限抗力的表达式.力学模型计算和物理模型实验得出的极限抗力结果一致.从板块极限平衡角度得出了反拱形底板优于平底板的量化指标.结果表明,反拱形底板安全系数大于平底板3倍以上.以某高拱坝的工程实例计算了安全系数.

The counter-arched slab in plunge pool keeps its integral stability by the thrust at spandrel when the load of jet-flow acts on it. It has the advantage that the resistance to pressure of concrete can be fully utilized. But the stability of flat slab depends only on the gravity and the anchor force. It is possible that the function of counter-arched slab does not form under specified condition because the construction crack exists along the direction of the arch ring and the non-uniform distribution of the flow load. For this reason, the possibility of the local failure of arch ring exists when a bigger local fluctuating load arises. Based on the concept of 'random arch', the mechanical model and the physical model for the limit stability of slab are set up. The local stability of the individual slab is analyzed and the formula of limit resistance for local stability of slabs is derivate. From limit balance, the quantitative factor of stability for counter-arched slab is obtained. The calculating and testing results indicate that the safety coefficient of local stability for counter-arched slab is three times greater than that of flat slab. Based on the study on stability for counter-arched slab in plunge pool of a high arch dam, the safety coefficient is calculated.