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隧道洞口段围岩风化破碎严重,施工难度大,且极易发生坍塌冒顶等安全事故。本文结合某高速公路隧道洞口不良地质情况,从受力和围岩塑性区两个方面详细分析了3种围岩加固方案的优劣,同时确定了该隧道洞口段围岩加固的最佳方案。研究表明:小导管与管棚注浆对初期支护剪力和弯矩影响不大,但对初期支护轴力有明显的降低作用,同时管棚注浆可使初期支护轴力分布更加均匀。管棚注浆结合径向注浆预支护与预加固方案下围岩仅在拱脚附近出现塑性区,围岩出现塑性范围区域最小。同时指出,针对本隧道洞口段不良地质情况,建议采用管棚结合径向注浆加固措施对隧道洞口段围岩进行处理。
The surrounding rock of the tunnel entrance section is seriously weathered and crushed, which makes it difficult to construct and is prone to safety accidents such as collapse and roof collapse. Based on the adverse geological conditions of a tunnel entrance, this paper analyzes the advantages and disadvantages of three kinds of surrounding rock reinforcement schemes from two aspects of stress and plastic zone of surrounding rock. At the same time, the best scheme of surrounding rock reinforcement at the tunnel entrance is determined. The results show that the small duct and pipe shed grouting have little effect on the initial support shearing force and bending moment, but obviously reduce the axial force of the initial support. At the same time, the grouting of pipe shed can make the initial support axial force distribution more Evenly. In the case of pipe roof grouting combined with the radial grouting pre-support and pre-reinforcement schemes, the plastic zone appears only in the vicinity of the arch foot and the plastic zone in the surrounding rock is the smallest. At the same time, it is pointed out that according to the unfavorable geological conditions of the tunnel mouth section, it is suggested that the pipe wall and the radial grouting reinforcement measures be adopted to treat the surrounding rock of the tunnel mouth section.