参数变异性对围护结构稳定性影响分析

Analysis of influence of parameters variability on retaining structure stability

利用可靠度分析方法代替传统的安全系数法来分析基坑围护结构的整体稳定性,考虑岩土参数的不确定性和空间变异性,对土性参数进行空间折减可显著提高可靠度分析的精度。结合工程实例,分析了参数均值和变异系数对基坑整体稳定性可靠度指标的影响。分析表明,可靠度指标β对土体黏聚力c、内摩擦角φ、地面超载q及支护桩嵌固深度hd的均值变化的敏感性较安全系数K对上述参数的敏感性强;c、φ及hd值的变异性对β值影响较大,地面超载较大时,其变异性对β影响较为显著;采用可靠度指标β评价基坑整体稳定性较安全系数K更加合理。

Considering uncertainties and spatial variability of soil parameters,the reliability analysis method can reflect objectively the real safety character of retaining structure for foundation pit engineering instead of the safety factor method.The reliability index increased and the variability of soil parameters decreased after being reduced by the random field theory.Compiled with project example,this paper provided the detailed analysis of the mean value and the variability of the design parameters which affected the stability of soil foundation pit.The results show that,the sensitivity of the parameters of cohesion c,angle of internal friction φ and the embedded depth hd which affected the reliability index β was much more than those affected the safety factor K.The reliability index β was affected significantly by the coefficients of variation δc,δφ,and δhd.The δq affected the reliability index β obviously when μq was large.It＇s reasonable to appraise the overall stability of retaining structure of foundation pit by reliability analysis method than by the safety factor method.