为了准确获得近接施工条件下围岩压力的计算方法,分析隧道净距对围岩应力和变形演化的影响机制,以351国道改建工程中沙滩头隧道施工为工程背景,采用极限上限分析法,建立了深埋并行近接隧道围岩压力分析模型。通过参数分析,确定了侧压系数和隧道净距对围岩压力的影响规律。通过对单洞隧道掘进以及近接施工隧道开展模拟,分析了净距影响下隧道围岩应力和变形场演化规律,以及中夹岩的稳定性。结果表明:隧道围岩垂直压力与侧压系数呈近似负指数关系,内外侧竖向围岩压力的相对斜率增大时,垂直压力逐渐减小;隧道近接施工时,环向应力场整体向既有隧道侧偏移,当隧道净距增加时,后掘进隧道在靠近既有隧道侧拱角形成的应力增量和最终顶板沉降量均逐渐减小;当隧道净距较小时,双洞掘进后,中夹岩呈现剪切破坏,当净距较大时,双洞侧向应力集中区的叠加效应减弱,中夹岩保持稳定。研究成果可为深埋近接隧道施工提供理论依据。

To accurately obtain the calculation method for surrounding rock pressure under adjacent construction conditions and analyze the impact mechanism of tunnel clear distance on the evolution of stress and deformation in the surrounding rock, this study takes the construction of the Shatantou Tunnel in the reconstruction project of National Highway 351 as its engineering background. The upper-bound limit analysis method was employed to establish a pressure analysis model for the surrounding rock of deeply buried parallel adjacent tunnels. Through parameter analysis, the influence patterns of the lateral pressure coefficient and tunnel clear distance on the surrounding rock pressure were determined.Through simulation of single-tube tunnel boring and adjacent construction tunnels, the evolution laws of stress and deformation fields in the surrounding rock under the influence of clear distance, as well as the stability of the middle rock mass, were analyzed. The results show that: The vertical pressure of the surrounding rock exhibits an approximately negative exponential relationship with the lateral pressure coefficient. As the relative slope of the vertical pressure between the inner and outer sides of the surrounding rock increases, the vertical pressure gradually decreases. Simulations of single-tunnel excavation and adjacent tunnel construction were conducted, revealing the evolution patterns of stress and deformation fields in the surrounding rock under the influence of tunnel clear distance, as well as an analysis of the stability of the middle rock pillar. During adjacent tunnel construction, the circumferential stress field shifts toward the existing tunnel. As the tunnel clear distance increases, the stress increment formed at the arch angle of the tunnel closer to the existing tunnel and the final roof settlement both gradually decrease. When the tunnel's clear distance is small, shear failure occurs in the middle rock pillar after dual-tunnel excavation. When the clear distance is large, the superposition effect in the lateral stress concentration zones of the two tunnels weakens, and the middle rock pillar remains stable.