大断面浅埋软岩隧洞快速掘进的可行性分析

Feasibility Analysis of Rapid Excavation of Large Section Shallow Buried Soft Rock Tunnel

大断面浅埋软岩隧洞开挖存在围岩强度低、自稳性差等棘手难题。为确保工作面安全高效施工,分析了“掘进机-破碎锤-铣挖机”相协调开挖施工工艺下的大断面浅埋软岩隧洞围岩稳定性。结合卡拉奇核电厂排水隧洞地质条件,基于弹塑性理论得出隧洞围岩变形理论极限位移;采用数值模拟分析隧洞围岩应力分布特征,表明拱部以上位置为围岩薄弱部位。经现场监测分析表明,采用“掘进机-破碎锤-铣挖机”相协调的施工工艺在开挖断面成形后,10 h内完成初期支护能够确保围岩变形处于稳定状态;工程应用表明“掘进机-破碎锤-铣挖机”相协调的施工工艺循环用时短,围岩扰动小,能有效保障施工安全,经济效益显著。

There are some difficult problems in the excavation of large section shallow buried soft rock tunnel,such as low strength of surrounding rock and poor self stability.In order to ensure the safe and efficient construction of the working face,the stability of surrounding rock of large section shallow buried soft rock tunnel under the coordinated excavation technology of"roadheader-breaking hammer-milling and digging machine"is analyzed.Combined with the geological conditions of the drainage tunnel of Karachi nuclear power plant,the theoretical limit displacement of the surrounding rock deformation of the tunnel is obtained based on the elastic-plastic theory.The stress distribution characteristics of tunnel surrounding rock are analyzed by numerical simulation,which shows that the position above the arch is the weak part of surrounding rock.The field monitoring analysis shows that the coordinated construction technology of"roadheader-breaking hammer-milling and digging machine"can ensure the stability of surrounding rock deformation by completing the initial support within 10 hours after the excavation section is formed.The engineering application shows that the coordinated construction process of"roadheader-breaking hammer-milling and digging machine"has short cycle time and small disturbance of surrounding rock,which can effectively ensure the construction safety and remarkable economic benefits.