重力式挡土墙抗滑稳定分析安全判据和标准

Safety criteria and standards for stability analysis of gravity retaining walls

探讨水利、交通等领域挡土墙设计规范中对抗滑稳定安全系数规定的允许值的合理性,认为其相应值与国外相关规定相比偏小。从理论上分析,使用抗力除以土压力的安全系数定义计算土压力相应的强度参数是标准值,而非经分项系数或安全系数折减后的标准值,其允许安全系数宜大于边坡等同类土方构筑物的相应值。认为建立在可靠度理论指导下的分项系数方法可以从根本上摆脱在安全判据方面存在的缺陷。在假定一级建筑物的允许可靠指标为3.7、土的黏聚力和摩擦系数变异系数分别为0.2和0.1的条件下,对一个特定的算例,填土的黏聚力、摩擦系数和基底的摩擦系数分项系数标定值分别为y_c=1.301,y_f=1.209和y_(fo)=1.170,应用提出的相对安全率判据,可以发现上述的分项系数标定值具有普适意义。该成果可以为相关规范的制订提供参考。

The allowable values of the factor of safety in gravity retaining wall design in various Chinese codes are discussed,and it is concluded that these allowable values are generally smaller than those adopted in many foreign country codes.Theoretically,the factor of safety is defined as the resistance divided by earth pressure,where the earth pressure is the one determined by using the non-corrected strength parameters instead of the reduced strength,and thus the resulting allowable factor of safety should be larger than that adopted in the design of the equivalent retaining structure.To resolve this problem,limit state design with partial factors is applied to retaining wall design problem.For Class 1 structures,its target reliability index is 3.7.Assuming the coefficients of variability of 0.2 and 0.1 for cohesion and friction,respectively,the calibrated partial factors are y_c = 1.301,y_f = 1.209 and y_（fo） = 1.170.The calibrated partial factors are validated by the ‘ratio of safety margin＇ theory proposed by the authors＇ research team.The discussion of this paper provides some useful guidelines for code makers.