基于围岩破坏特征的单洞四车道公路隧道围岩分级修正研究

Study on Correction of Surrounding Rock Classification for Single-tube Four-lane Highway Tunnel Based on the Failure Characteristics of Surrounding Rock

为了对单洞四车道公路隧道围岩分级方法进行研究,首先通过调研对隧道开挖围岩破坏过程进行分析,得出围岩由好到差的3种破坏特征;其次采用数值模拟方法,对不同围岩级别条件下的多种工况进行计算,根据结果对围岩破坏特征进行研究,并据此进行围岩参数分级以及隧道开挖工法判定,最后结合现场测试进行验证。研究结果表明:(1)将围岩塑性区骤增、拱部出现受拉区、承载力不足导致整体失稳3种围岩破坏特征作为Ⅲ级、Ⅳ级、Ⅴ级围岩分级的依据;(2)根据数值计算结果以及结构破坏特征分析,单洞四车道公路隧道Ⅱ级围岩条件适用全断面法开挖,Ⅲ级围岩适用台阶法开挖,Ⅳ级围岩适用CD法开挖,Ⅴ级围岩适用CRD法开挖;(3)根据计算结果分析提出了结合单洞四车道公路隧道围岩破坏特征修正的围岩分级BQ值。

In order to investigate the surrounding rock classification method that takes account of the excavation method for single-tube four-lane highway tunnel,the failure process of surrounding rock in the tunnel excavation process is analyzed after a field survey,to identify 3 types of failure characteristics of surrounding rock ranked from good to poor.Then several cases under different surrounding rock classes are calculated by using the numerical simu⁃lation method.The failure characteristics of surrounding rock are investigated according to the calculation results.On this basis,the surrounding rock parameters are classified and the tunnel excavation method is determined.At last,the method is demonstrated through field test.As the study results indicate:(1)The 3 failure characteristics in⁃cluding abrupt increase of plastic zone of surrounding rock,formation of tension zone at the arch and overall instability resulting from insufficient bearing capacity are used as the basis for classifying surrounding rock into ClassesⅢ,ⅣandⅤ.(2)For single-tube four-lane highway tunnel,according to the results of numerical calculation and analysis of structural failure characteristics,the full face method is suitable under ClassⅡsurrounding rock condition,the bench-cut method under ClassⅢsurrounding rock condition,the CD method under ClassⅣsurrounding rock con⁃dition,and CRD method under ClassⅤsurrounding rock condition.(3)After analysis of the calculation results,the BQ value of the surrounding rock classification is proposed that takes account of the correction of surrounding rock failure characteristics of single-tube four-lane highway tunnel.