第四系富水红砂岩地层隧道围岩变形特征研究

Research on the Deformation Characteristics of Tunnel Surrounding Rock in Water-rich Quaternary Red Sandstone Stratum

研究目的:富水条件下砂岩地层隧道开挖极易产生大变形。本文以蒙华铁路阳城隧道第四系富水红砂岩地层围岩大变形段为研究对象,通过室内试验、现场试验及数值模拟等方法,对围岩变形特征进行研究,从而提出围岩大变形的整治措施。研究结论:(1)对地层围岩认识有限、支护与降水措施不到位,导致围岩背后脱空溜砂,是产生大变形的主要原因;(2)工法变更辅以加密降水能有效控制围岩变形,拱顶沉降、水平收敛降低60%～65%,掌子面挤出降低50%;(3)现场试验监测结果显示,大变形整治措施、工法变更辅以加密降水行之有效,围岩变形量皆在规范允许范围内,后续施工段拱顶沉降监测值与数值模拟值相差18%,拟合较好,数值模拟有一定可靠度;(4)本文提出的围岩大变形相关整治措施,可为类似地层隧道围岩大变形整治、控制围岩变形及隧道安全施工提供借鉴。

Research purposes： During the construction of sandstone tunnels under water-rich conditions,surrounding rocks are easily deformed. Taking the large deformation zone of surrounding rock in water-rich quaternary red sandstone formation of Mengxi-Central China Railway Yangcheng Tunnel as the research object,this paper analyzed deformation characteristics of surrounding rock by indoor testing,on-site monitoring and numerical simulation methods,put forward the remediation measures of large deformation of surrounding rock.Research conclusions：（1） The lack of understanding of surrounding rock lithology,the insufficient of support and precipitation measures,result in the escape of sand behind the surrounding rock,which is the main reason for large deformation;（2） Changes in work methods combined with intensive precipitation can effectively control the deformation of the surrounding rock,reducing the vault settlement and horizontal convergence by 60% ～ 65%,and reducing the extrusion displacement of the tunnel face by 50%;（3） The field test monitoring results show that large deformation remediation measures and changes in construction methods supplemented by intensive precipitation are effective,thesurrounding rock deformation is within the allowable range of the specification,and the monitoring value of the vault settlement of the subsequent construction segment is different from the numerical simulation value by 18%. The fitting degree and the numerical simulation reliability are good.（4） The relevant remediation measures are put forward,which can provide reference for similar large-scale tunnel surrounding rock large deformation remediation and safe construction.