下穿高速双孔并行隧道可靠度分析

针对地下结构可靠度分析中功能函数不能显示表达的特点,提出基于三维有限元的可靠度分析方法。以下穿高速双孔并行隧道为例,根据三维有限元计算结果,分别以DP2与DP3准则作为塑性屈服的判定准则,采用遗传算法选取样本点构建二次响应面模型,通过对Monte Carlo法,基于BP神经网络的Monte Carlo法,中心点法,JC法和遗传算法得出的可靠度指标的比较分析,得出遗传算法的运用可显著提高响应面模型的逼近精度,中心点法计算出的可靠度指标误差较大,Monte Carlo法、BP-Monte Carlo法、JC法及遗传算法求得的可靠度指标精度相近,JC法因操作简便、计算精度高可广泛用于地下结构的可靠度分析。基于遗传算法选取的样本点构建响应面模型,以JC法计算地下结构的可靠度分布,得出在公路线荷载作用下,衬砌上下两侧向内变形,上下两侧围岩应力释放多,可靠度相应增大;衬砌左右两侧向外变形,左右两侧围岩应力增大,可靠度相应减小;并行隧道的相互影响导致邻近另一隧道侧的衬砌可靠度较小。

Reliability Analysis of Two Paralleled Tunnels Crossing Beneath a Highway

Considering the difficulty of setting up the performance function in reliability analysis of underground structure, a method based on the 3D-fi-nite element method for reliability analysis is put forth. Taking two paralleled tunnels crossing beneath a highway as an example, the DP2 and DP3 criteri-a as the norm to judge plastic yield respectively, it builds the quadratic response surface models through the sample points selected by genetic algorithm. Through comparison and analysis of the reliability index calculated by the Monte Carlo, the Monte Carlo based on the BP neural network, center point method, JC method and genetic algorithm, the use of genetic algorithm in selecting sample points can improve the accuracy of the response surface mod-els significantly; the relative error of the reliability indexes calculated by center point method is large; the accuracy of reliability index calculated by Monte Carlo, BP-Monte Carlo, center point method, JC method and genetic algorithm is approximate; JC method can be broadly used in reliability calcu-lation of underground structure for its simple operation and high accuracy. Based on the sample points selected by genetic algorithm to construct response surface models, it draws from the distribution of reliability index of substructure calculated by JC method that under the highway line load the inward de-formations of the upper and lower sides of the lining leading to the decrease of stress result in the increase of reliability index of the corresponding sides of surrounding rock and the outward deformations of the left and right sides of the lining leading to the increase of stress result in the reduction of reliability index of the corresponding sides of surrounding rock; the reliability index of the lining near the other tunnel decreases as a result of interaction of the two paralleled tunnels.