水垫塘波面高度对不利工况下护坡安全的影响

Effect of Wave Surface Elevation in Cushion Pool on the Slope Lining Safety Under Adverse Operating Condition

水垫塘护坡板块破坏的工程事故近年来时有发生,依托乌东德水弹性模型,考虑护坡板块处于排水失效且止水局部破坏的最不利工况,对护坡靠基岩一侧表面(背水面)和靠水垫塘一侧表面(迎水面)的时均及脉动压强差进行试验研究,结果表明板块背水面和迎水面的水位差导致的渗流压力与脉动压力不相关性所产生的瞬时脉压差共同构成了导致护坡破坏的上举力,渗流压力主要受水垫塘内波面高度的影响。因此,对水垫塘内波面高度的空间和概率分布进行试验研究。从空间分布上来说,不同工况下,普遍具有水舌落水点附近波面高度最大,与水舌落水点桩号相近的边坡处波面高度次之,随着桩号向坝下静水区和二道坝方向变化,则波面高度逐渐减小的特点。从概率分布上来说,借鉴海浪统计学的研究,采用Gram-Charlier级数型函数描述其概率分布,通过数据拟合发现,该函数相比正态分布能更好地符合渗流压力(波面高度)的实际概率分布。对于迎、背水面所受的脉动压力,认为其服从正态分布。因此,护坡板块的破坏是一列服从Gram-Charlier级数型分布的随机过程(渗流压力)和两列相互独立的服从正态分布的随机过程(迎、背水面脉动压力)共同作用的结果。考虑护坡板块的受力特点和破坏机理,分析了传统的水垫塘安全监控指标的适用性及可能产生的偏差。

Recently,as the structure damage of slope lining occurred,experimental investigation on the difference between the mean pressures and the fluctuating pressures on the back and front sides of slope lining plate is carried out based on the Wudongde Hydroelastic model.The most ad- verse operating condition is simulated when the water stop and drainage facilities partially and totally invalid,respectively.Results showed that both the seepage pressure and the instantaneous fluctuating pressure contribute to the uplift force which causes the damage of the slope lining plate.The seepage pressure induced by the water level was different between the back and front side of slope lining plate,and it was mainly af- fected by the wave surface elevation in cushion pools： Therefore,we studied the space and probability distribution of the wave surface elevation.Experimental results showed that the wave elevations near the water entry were higher than those near the slope protection with similar reference number as the water entry.Moreover, as the reference number increased （or decreased） from the water entry,the water elevation gradu- ally decreased （or increased）.Inspired by the studies of ocean wave statistics,G-ram-Charlier series distribution was adopted to describe the probab- ility density distribution of the wave surface elevation.According to the data fitting,Gram-Charlier series distribution was more consistent with the actual situation than Normal distribution.It was considered that the fluctuating pressures acting on the front and back sides of the slope lining plateobey the normal distribution.Both the stochastic process in which the random variables obey Gram-Charlier series distribution and two mutually independent Gaussian stochastic processes contributed to the destruction of slope lining plate.Comprehensively considering the load characterist- ics and the failure mechanism,the applicability and the probable error for the traditional safety monitoring index of cushion pool were analyzed.