特大断面山岭隧道出洞口段开挖技术对比分析:以燕山地区汗沟2号隧道为例

Comparative Analysis of Excavation Techniques for Exit Section of Large Cross Section Mountain Tunnel:Taking No.2 Hangou Tunnel in Yanshan Area as an Example

为研究不同出洞开挖施工方法对特大断面山岭隧道洞口段围岩变形影响,以燕山地区汗沟2号隧道为依托工程,利用ABAQUS有限元软件建立数值模型,分析了双线隧道洞口段先行右洞采用超前小导洞开挖出洞和后行左洞采用三台阶七步开挖进洞情况下的围岩水平收敛、拱顶沉降、底部上拱、地表沉降、塑性区分布以及衬砌支护应力等影响。结果表明:小导洞开挖过程中围岩变形较小;由洞内向洞外与洞外向洞内扩挖右洞小导洞的围岩变形规律基本一致,前者对于山岭隧道洞口段施工具有优越性;左右洞贯通后,右隧最大水平收敛、拱顶沉降、底部上拱、地表沉降和衬砌最大主应力分别为1.35 mm、3.91 mm、2.88 mm、3.39 mm和0.11 MPa,左隧分别为1.52 mm、5.57 mm、2.67 mm、5.34 mm和0.35 MPa,超前小导洞开挖工法更有利于控制围岩变形,而三台阶进洞开挖下围岩塑性应变以及地表沉降较大。研究结果可为同类工程提供一定理论依据和指导,实现特大断面山岭隧道安全、高效出洞作业。

In order to study the influence of different excavation methods on the deformation of surrounding rock at the entrance of a super large cross-section mountain tunnel,a numerical model was established using ABAQUS finite element software based on the Hangou No.2 Tunnel in the Yanshan Area.The horizontal convergence,arch settlement,bottom arch,and surface settlement of the surrounding rock were analyzed when the right tunnel was excavated with a leading small guide tunnel and the left tunnel was excavated with three steps and seven steps,respectively.The distribution of plastic zone and the influence of lining support stress.The results indicate that the deformation of the surrounding rock is relatively small during the excavation process of the small pilot tunnel.The deformation law of the surrounding rock of the right small pilot tunnel is basically the same when expanding from the inside to the outside of the tunnel and from the outside to the inside of the tunnel.The former has advantages for the construction of the mountain tunnel entrance section.After the left and right tunnels are connected,the maximum horizontal convergence,arch settlement,bottom arch,surface settlement,and maximum principal stress of the lining of the right tunnel are 1.35 mm,3.91 mm,2.88 mm,3.39 mm,and 0.11 MPa,respectively.The left tunnel is 1.52 mm,5.57 mm,2.67 mm,5.34 mm,and 0.35 MPa,respectively.The advanced small pilot tunnel excavation method is more conducive to controlling the deformation of the surrounding rock,while the plastic strain of the surrounding rock and surface settlement are greater under the excavation of the three step tunnel.The research results can provide a certain theoretical basis and guidance for similar projects,and achieve safe and efficient excavation operations for large cross-section mountain tunnels.