黏土质隧道围岩抗剪强度参数的概率分布及优化实例

PROBABILITY DISTRIBUTION AND OPTIMIZING EXAMPLE OF SHEAR STRENGTH PARAMETERS OF SURROUNDING ROCK IN COHESIVE SOIL TUNNEL

以长序列隧道浅埋段第四系坡残积黏性土的抗剪强度参数试验数据为基础,运用皮尔逊X2检验方法和有限比较法分析黏性土隧道围岩抗剪强度参数的概率分布类型并计算其所服从概率分布的概率密度函数。结合具体工程实例,运用贝叶斯(Bayes)方法对黏聚力、内摩擦角进行优化,探讨变异系数与概率分布类型选取之间的关系。研究结果表明:黏土质隧道围岩黏聚力和内摩擦角的最优分布概型分别为正态分布、对数正态分布;极值I型分布不适宜作为坡残积黏土质围岩黏聚力、内摩擦角的概率分布;当变异系数较小时,内摩擦角选用对数正态分布概型与正态分布、β分布相差较小;对于黏聚力,建议选择最优概型;黏聚力、内摩擦角经Bayes方法优化后变异系数减小,数据更趋于合理。

Taking a long sequence test data of shear strength of quaternary clinosol and residual cohesive soil in shallow-buried tunnel section as a base,the authors studied the probability distribution of the parameters and fitted their probability density function by X 2 check method and finite contrast method,used Bayes method to optimize cohesion and internal friction angle of a soil tunnel,and discussed the relation of the probability distribution and variation factor.The research results show that optimum probability distribution of the cohesion is normal distribution,but the internal friction angle′s is logarithm normal distribution.Extreme type I isn′t equal to be probability distribution of cohesion and internal friction angle of clinosol and residual cohesive soil surrounding rock.When variation factor is lower,optimum probability distribution,normal and Bata distribution have little influenc on the internal friction angle,but whenever optimum probability distribution is best choice for cohesion.Variation factors of cohesion and internal friction angle minish and the data are more reasonable after they are optimized through Bayes method.