考虑初支滞后性的软弱地层隧道进洞段管棚注浆加固效果研究

Research on Grouting Reinforcement Effect of Pipe-roof Tunnel Entry Section in Soft Stratum Considering Hysteresis Effect of Initial Support

依托江西遂大高速圆村隧道,建立了将管棚与加固区的支护作用分开研究,并考虑初支滞后效应的隧道开挖的三维数值模型,将模型分为注浆加固区与无注浆加固区,对比分析了隧道动态施工过程中隧道围岩及各支护结构的受力及变形特征,并结合依托工程的现场监测数据,对模型的合理性和可行性进行了验证。结果表明:隧道开挖后,管棚的受力与进洞距离有关。在刚进洞时,管棚根据受力的不同沿纵向可分为3段:套拱位置的受压区Ⅰ、掌子面前方的受拉区Ⅱ及最后的受压区Ⅲ。进洞一定距离后,根据受力的不同沿纵向可分为4段:套拱位置的受拉区Ⅰ、掌子面后方的受压区Ⅱ、掌子面前方受拉区Ⅲ及最后的受压区Ⅳ。当管棚支护区域全部开挖完成时,根据受力的不同沿纵向可分为两段:套拱前方的受拉区Ⅰ及掌子面后方的受压区Ⅱ。隧道进洞开挖时,会首先在仰坡坡脚形成塑性区,管棚注浆加固能抑制塑性区的产生和发展,防止仰坡发生失稳。

Based on the Yuancun Tunnel of Jiangxi Suichuan—Dayu Expressway,a three-dimensional numerical model of tunnel excavation is established to study the support effect of the pipe-roof,which researches reinforcement area separately and considers the hysteresis effect of initial support.The model is divided into grouting reinforcement area and non-grouting reinforcement area to compare and analysis the stress and deformation characteristics of the tunnel surrounding rock and various support structures during the dynamic construction process.Combining with on-site monitoring data of the actual project,the rationality and feasibility of the model are verified.The results indicate that after tunnel excavation,the stress on the pipe-roof is related to the distance from the tunnel entry:when entering the tunnel firstly,the pipe-roof can be divided into three sections along the direction of tunnel excavation:the compression section at the entrance casing arch?,the tension section Ⅱ in front of the tunnel face and the final compression section Ⅲ.After entering the tunnel for a certain distance,it can be divided into four sections:the tensile section at the entrance casing arch?,the compression section Ⅱ behind the tunnel face,the tensile section Ⅲ in front of the tunnel face,and the final compression section Ⅳ.When all the excavation of the pipe-roof support area is completed,it can be divided into two sections:the tensile section in front of the entrance casing arch,the compression section Ⅱ behind of the tunnel face.When excavating a tunnel,a plastic section will first be formed at the foot of the front slope.Pipe-roof grouting reinforcement can suppress the generation and development of the plastic section and prevent instability of the front slope.