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在大跨小净距偏压隧道施工中,合理的施工方法和施工工序对保证围岩稳定性和支护结构受力有很大影响。结合大跨小净距偏压隧道的结构形式,总结了其受力特点,并建立大跨小净距隧道在Ⅴ级围岩浅埋偏压环境下的有限元数值模型,分别采用双侧壁导坑法、CRD法对不同施工工序下围岩位移、应力和塑性区等进行对比分析。结果表明:CRD对控制隧道水平收敛较为有利,但隧道拱脚处应力集中现象明显,围岩塑性区较大,双侧壁导坑法对控制隧道拱顶下沉较为有利;先开挖浅埋侧隧道时中岩柱两侧拱肩、拱腰应力集中较大,而先开挖深埋侧隧道时隧道拱脚应力集中较大;先开挖隧道内侧时,洞周围岩位移较大。
In the construction of large-span and small-spacing biased tunnels, reasonable construction methods and construction procedures have a great impact on the stability of surrounding rock and the supporting structure. Combined with the structure of the large-span and small-spacing biased tunnel, the stress characteristics of the tunnel are summarized, and the finite element numerical model of long-span and small clear-distance tunnel under shallow buried bias environment of Grade V surrounding rock is established. Pilot pit method and CRD method were used to analyze the displacement, stress and plastic zone of surrounding rock under different construction procedures. The results show that CRD is more favorable for controlling the horizontal convergence of the tunnel, but the stress concentration at the arch foot of the tunnel is obvious, and the plastic zone of the surrounding rock is larger. The double-side wall pilot pit method is more advantageous to control the tunnel dome dwelling. Side tunnels have large stress concentration on the spandrels and arches on both sides of the mid-rock columns. However, the stress concentration on the arch foot of tunnels is larger when excavating the deep-buried side tunnels first. When the inside of the tunnel is excavated first, the displacement of rock masses is larger.