Research on Pre-Reinforced Regions and Strength Parameters of Shallow Tunnels in Weak Strata

Abstract

Safety coefficient and surface settlement were chosen as evaluation indictors for non-self-stabilizing weak strata and basic self-stabilizing weak strata. Fluid mechanical interaction is used to analyze the pre-reinforcement scope and strength parameters in this numerical method. Moreover, the scope of lateral reinforcement is discussed based on the damage modes of tunnels in stratums with different depths. The study shows the following: (1) the thickness and stiffness of reinforced regions must meet certain conditions simultaneously to obtain a better surface settlement; (2) the thickness of reinforced region must be approximately 2–2.5 m and the stiffness of reinforced region should be increased until it is six times that of the original stratum to guarantee stable stratum stability in non-self-stabilizing stratums; (3) the thickness should be 1.5–2 m for basic stability strata, and the stiffness should be increased until it is five times that of the original stratum. Finally, the scope of consolidation given the damage mechanism of formation is verified through numerical calculation.