大断面深埋软岩隧道开挖方法适应性研究

Research on adaptability of excavation method of large section deep-buried soft rock tunnel

为研究大断面隧道在深埋软岩条件下采用不同工法开挖的适应性,依托郑万高铁巴东隧道项目,运用Midas GTS NX分别模拟了三台阶法、台阶法+临时仰拱与CD法在深埋软岩中的开挖过程,并对3种开挖方法力学效应进行分析。结果表明3种工法在深埋软岩隧道施工中,围岩的最小主应力、最大位移和塑性区均出现在仰拱部位,而仰拱变形是反应开挖时围岩稳定性的重要因素。台阶法+临时仰拱对收敛位移控制较好,适用于水平应力对支护结构影响较强的地层,建议在洞口等浅埋段采用。CD法支护结构应力较大,不利于围岩稳定。三台阶法支护结构受力较小,并对仰拱变形中超前位移控制最佳,为现场施工提供了指导。

To research the adaptability of large-section tunnels in deep-buried soft rock conditions with different construction methods,we take Badong Tunnel Project of Zhengwan High-Speed Rail as example,employ Midas GTS NX to simulate the three-step method,step method+temporary invert and CD method to simulate the deep-buried soft rock excavation process.The analysis results show that the minimum principal stress,maximum displacement and plastic zone of the surrounding rock in the construction of deep soft rock tunnels with the three construction methods appearing in the invert position,and the invert deformation is an important factor that reflects the stability of the surrounding rock during excavation.The step method+temporary invert has better control of the convergence displacement,and is suitable for strata where horizontal stress has a strong influence on the supporting structure.It is recommended to be used in shallow buried sections such as cave entrances.The stress of the CD method support structure is relatively large,which is not conducive to the stability of the surrounding rock.The three-step support structure is less stressed and has the best control of the advance displacement,which provides guidance for on-site construction.