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受明显的层状结构影响,加之材料参数和动荷载的双重随机性,动力条件下碾压混凝土重力坝的层间抗滑稳定可靠度问题值得关注。考虑地震波频谱特性、峰值加速度、坝体材料参数的随机性,统计概化出地震作用下坝体的潜在滑动失效路径;在特定地震动作用下,基于随机有限元分析结果,采用刚体极限状态判断准则和响应面法构建失效路径的动力抗滑稳定功能函数,进而求得其抗滑稳定可靠指标;接着考虑不同失效路径的相关性,用Ditlevsen窄界限公式估算体系的可靠度;最后,考虑地震动荷载的随机性,采用基于全概率公式的数值拟合积分方法求解大坝抗滑稳定体系的动力可靠度。研究结果表明,动力条件下,当水平地震系数大于0.2时,重力坝层间抗滑体系可靠度不再由建基面失效路径决定,而是由下游折坡处层面的失效路径决定。该方法数学意义明确,实用性强。
Affected by the obvious layered structure, coupled with the double randomness of material parameters and dynamic load, the reliability of anti-sliding stability between layers of RCC gravity dam under dynamic conditions deserves attention. Considering the spectrum characteristics of seismic wave, the peak acceleration and the randomness of the dam material parameters, the potential sliding failure path of the dam under earthquake action is statistically generalized. Based on the results of stochastic finite element analysis and the rigid body limit state Criterion and response surface method to construct the sliding stability function of the dynamic path of the failure path, and then to obtain the reliable index of the anti-sliding stability. Then, considering the correlation of different failure paths, the reliability of the system is estimated by the Ditlevsen narrow bound formula. Finally, The randomness of dynamic loads, the numerical fitting integral method based on total probability formula is used to solve the dynamic reliability of the dam anti-sliding stability system. The results show that when the horizontal seismic coefficient is greater than 0.2 under dynamic conditions, the reliability of the anti-skidding system between gravity dam is no longer determined by the failure path of the foundation, but is determined by the failure path at the downstream slope. The method has clear mathematical meaning and strong practicability.