进洞一直是隧道施工的关键环节,而洞口工程的顺利完成是暗洞正常施工的前提.目前,采用超前管棚支护、超前小导管注浆等超前支护方式基本能够保证隧道顺利进洞,但是大部分隧道进洞后在洞口段均会出现初期支护沉降变形较大的现象.山西省高(平)-陵(川)高速公路郭家川2#隧道洞口段围岩极其软弱破碎,在隧道采用超前管棚支护顺利进洞后,为了防止洞口段初期支护再次出现较大的沉降变形,提出在洞口段采用联合支护的方案,即将洞口段初期支护的钢拱架与护拱连接,并加强初期支护钢拱架之间的纵向连接,实践证明此方案是切实有效的.分析对比表明,对于浅埋软弱破碎围岩隧道,联合支护方案能够有效地减小洞口段初期支护的变形量,保证隧道结构的稳定性,从而保证隧道安全、快速进洞.%Entrance excavation is always the key link of tunnel construction, the smooth completion of tunnel entrance is the premise of normal tunnel construction. The surrounding rock is extremely weak and broken at tunnel entrance of Guojiachuan No.2 tunnel on Gao (Ping) - ling (Chuan) Highway of Shanxi Province. After adopting advance pipe-roofing at the entrance, combined support of steel arch and a protective arch rib were adopted, the longitudinal connection of steel arches of primary support was reinforced, which proved to be efficient. The combined support can reduce the deformation of primary support at the entrance of the shallow tunnel in weak broken surrounding rocks, ensuring the stability of tunnel structure and the construction of tunnel entrance.
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