强度参数统计特性对边坡稳定可靠性的影响

Effect of strength parameters statistical property on slope stability reliability

由于对边坡强度参数统计特性考虑不全面,使得边坡可靠性指标计算值偏小,对应的失效概率偏大,常常超过10%,设计中难以采纳,造成地基可靠度规范的制定和执行进展缓慢。以某高速公路全风化花岗岩土质高边坡为工程背景,在分析土质参数统计特性的基础上,采用极限平衡理论和蒙特卡罗模拟法,系统地分析了土质强度参数的均值不定性、变异性、相关性、区间特性和空间变化性等对边坡稳定可靠性的影响。结果表明:土性参数的各种统计特性对边坡稳定可靠性均具有不同程度的影响。可靠性指标计算值随抽样距离的减小而增加,随c或φ均值的增大而增加,随c和φ的变异系数的增大而减小,随c和φ相关系数绝对值的增大而增加,考虑区间性后可靠性指标计算值也明显变大。即变异性对边坡稳定不利,而相关性、区间性和空间变化性对边坡稳定有利。因此,准确而全面地考虑土质参数的统计特性,尤其是在参数变异性和相关性的基础上加以考虑土性参数空间变化性和区间性会更加符合工程实际,且计算结果趋于安全,有利于地基可靠度规范的推广运用和边坡工程的安全评价。

Without comprehensive consideration of the strength parameters statistical properties,the slope reliability index calculation value become smaller and the failure probability become larger,often more than 10%,which was difficult to adopt in design.Hence,the foundation reliability norm＇s formulate and implement made slow progress.Take a completely weathered granite soil slope of an expressway as engineering background,and based on the analysis of the statistical characteristics of soil parameters,the limit equilibrium theory and monte carlo simulation method were used to systematically analyze the soil strength parameters＇ mean uncertainty,variability,correlation and interval characteristics and spatial variability of impact on the reliability of the slope stability.The resultsshowed that all kinds of statistical features of soil parameters had varying degrees impact on slope stability reliability.The reliability index calculation value increased with the decrease of the sampling distance,increased with the increase of the mean values of c orφ,decreased with the increase of the variation coefficientc andφ,increased with the increase of the correlation coefficient absolute value of candφ,and the reliability index calculation value became obvious bigger when interval characteristics were considered.The findings indicated that variability was adverse to the slope stability and the correlation,interval characteristics and spatial variability were good for the slope stability.Therefore,with accurate and comprehensive consideration of the soil parameters statistical features,especially with the consideration of space variability and interval characteristics on the basis of the consideration of parameters variability and correlation will be more in line with the engineering practice,and the calculation results tend to be more reliable.It is advantageous to the adopt reliability norm and safety evaluation of slope engineering.