基于现场实测的绢云母片岩隧道变形与受力特征

Deformation and Mechanical Characteristics of Sericite Schist Tunnel Based on Field Measurement

绢云母片岩是西南地区普遍存在的复杂地质软岩,遇水易软化、泥化,在该中地层条件下施工的隧道普遍出现软岩大变形问题,处理不当还会造成塌方,极易造成严重后果。以实际工程为载体,通过现场试验,研究绢云母片岩隧道的变形与受力特征。研究结果表明:三台阶开挖造成围岩压力的多级释放,每台阶开挖后围岩压力均经历快速增长与缓慢增加两个阶段,围岩压力总体呈现出“右上、左下大,右下、左上小”的非对称分布;初期支护钢架以受压为主,应力“上大下小”分布,右拱腰处钢架压应力最大237. 4 MPa,大于钢架抗压强度设计值;围岩整体向内挤压,隧道呈现“上大下小”不对称变形,右拱腰处最大变形量325 mm,大于预留变形。研究指出了施工过程中的安全隐患,并为绢云母片岩隧道的设计、施工提供了数据参考。

Sericite schist is a kind of complex soft rock in southwest China,which is easy to soften and muddy when exposed to water.Large deformation of soft rock is a common problem in tunnel construction under this stratum.Improper treatment will also cause collapse,which is extremely easy to cause serious consequences.The deformation and stress characteristics of sericite schist tunnel are studied by field tests with practical engineering as the carrier.The results show that the three-step excavation leads to the multi-stage release of the surrounding rock pressure.After each step excavation,the surrounding rock pressure goes through two stages of rapid increase and slow increase,and the surrounding rock pressure generally presents an asymmetric distribution of "larger right upper and lower left,and smaller right lower and upper left".The steel arch is dominated by compression,and the stress distribution is "large in the top and small in the bottom".The compression stress of the steel frame at the right arch waist is 237.4 MPa,which is greater than the designed value of the steel frame's compressive strength.As the surrounding rock is extruded inward as a whole,the tunnel presents the asymmetric deformation of "big on the top and small on the bottom".The maximum deformation at the right arch waist is 325 mm,larger than the reserved deformation.The hidden danger in the construction process is pointed out,and data reference for the design and construction of sericite schist tunnel are provided.