公路隧道施工过程分析及支护参数评价

在复杂地质条件下的隧道工程施工一般采用分步开挖法,围岩及支护结构的最不利承载状态往往发生在初期支护闭合之前,因此有必要对施工过程进行模拟计算。介绍了施工过程有限元数值模拟的方法,通过用设置释放系数的方法来模拟释放荷载的发展,对地层材料、锚杆加固区、喷射混凝土层及钢支撑的有限元模型的建立也进行了探讨。通过ANSYS对两种开挖方式进行了模拟分析,发现施工顺序对围岩的稳定及支护结构的受力影响很大,合理的施工开挖顺序应使围岩尽早构成承载环以分担更多的释放荷载,同时支护结构也应尽早构成承载性能好的拱形结构。加固区围岩强度的提高可使围岩分担更多的释放荷载,可以明显减小支护结构的受力。在云南保腾高速公路勐连隧道的施工中,该分析评价得到了较好的应用,很好地指导了隧道在软弱围岩地层的施工,取得了较好的效益。

Analysis on the Construction Process of the Highway Tunnel and the Evaluation of the Supporting Parameters

Step-by-step excavation method is applied to the tunnel engineering construction under the complex geological conditions. The most unfavorable loading state of the surrounding rock often happens before the closing period of initial sup- porting structure, so it is necessary to carry out the construction process simulation. This paper introduces the finite element numerical simulation method of the construction process, which simulates the development of released load by setting re- lease coefficient, and also discusses the establishment of the finite element model for stratum material, bolt anchorage area and the steel support. It is found that the stability of surrounding rock and stress of the supporting structure are greatly in- fluenced by the construction sequence through ANSYS analysis of two excavation methods, rational construction excavation sequence should enable the beating ring to form as soon as possible to share more loading. At the same time a good arch structure with good performance should also be constituted by the supporting structure. More released loading will be shared by surrounding rock by the increment of the strength of reinforcement area; the stress of the supporting structure can obvi- ously be reduced. In the construction of the Baoshan-Tengchong Expressway in Yunnan Province, the analysis is well applied which gives good guideline to the construction of the tunnel in weak rock formation, and achieves good benefits.