偏压隧道偏压应力比特征分析

Characteristic Analysis on Stress Ratio of Unsymmetrical Load Tunnel

偏压隧道是公路和铁路建设中经常遇到的隧道类型,由于其受力的不对称性及设计、施工的特殊性,一直是隧道施工研究的热点。以往针对偏压隧道的研究主要集中在偏压隧道的成因、围岩稳定性、应力应变分布规律及施工影响等方面,但缺少对偏压隧道偏压应力比以及公路、铁路设计规范给出条件的偏压应力比的研究,而且公路和铁路设计规范中给出的偏压隧道对应的坡面倾角和隧道埋置深度缺少相关理论来支撑。本文针对铁路双线隧道设计规范给出的临界坡度和覆盖层厚度条件,采用数值模拟的方法,求出地形偏压隧道对称位置的应力比值,定量分析了规范给定条件下偏压应力比的特征值。结果表明:在保证安全的前提下,当Ⅲ级围岩拱肩应力比大于7.45、Ⅳ(土)级围岩拱肩应力比大于2.23、Ⅳ(石)级围岩拱肩应力比大于3.34、Ⅴ级围岩拱肩处应力比大于1.06时,可将隧道考虑成偏压隧道,从而为定量判别偏压隧道提供理论依据。

Unsymmetrical load tunnel is a common type encountered in highway and railway construction.Because of its stress features,it is difficult to design and construct unsymmetrical load tunnel.Many researches focus mainly on stress distribution of unsymmetrical load tunnel,the causes of unsymmetrical load tunnel,surrounding rock stability,stress and strain distribution and construction affection etc.Seldom study focus on unsymmetrical load stress ratio and on conditions of unsymmetrical load stress ratio under the condition given of highway and railway design code.In this paper,based on the critical grade and coverage depth corresponding to the condition of the design code of double track railway tunnels,the stress ratios of the symmetrical position of the tunnel were calculated by means of numerical simulation.The results show that:under the premise of safety,when the stress ratio at arch shouldesr of gradeⅢsurrounding rock is greater than 7.45,the stress ratio of gradeⅣ(soil)surrounding rock is greater than 2.23,the stress ratio of gradeⅣ(rock)surrounding rock is greater than 3.34,and the stress ratio of gradeⅤsurrounding rock is greater than 1.06,the tunnel can be considered as an unsymmetrical load tunnel.The quantitative analysis results under the condition of railway tunnel design code provide a theoretical basis for the quantitative identification of the unsymmetrical load tunnel.