Study On Construction Technique Of Large-Span Tunnel Of Huang Ta Highway

Because the large-span tunnel the excavated section is big, the shape is flat, the stability of the adjacent rock is bad, the tunnel construction increases difficulties of distortion and the stable control. If we do it carelessly, it will create the landslide and safety incident. Therefore, the research on the large-span tunnel's construction technique has the very vital significance.The present paper take the large-span tunnel in Huangta-highway as the object of study. Through research on the large-span tunnel construction craft and disease managenment, we get some results as follows:the large-span tunnel's construction methods must be flexible, needs to adopt the corresponding methods to the different rank adjacent rock sector, also needs to adjust promptly in the special sector. The enter of great span tunnel is difficulty and important during the construction, generally uses a set of arch to coordinate the large pipe shed method to advanced support, carries on the pre-reinforcement after the enter section .According to the actual adjacent rock condition chose appropriate excavation method, specially it has bias situation in enter section, but it also needs to make the bias retaining wall to reduce the bias harm. The monitoring measurement in the tunnel construction security and disease management have played a vital role.In Changgan-1st tunnel, through the spot inspection and the adjacent rock displacement gauging, we judge the time of the distortion scope, the tendency to carry on the instruction for the project emergency. Through the steel bar meter which installs to the temporary steel support carries on the strain gauging ,we obtain the temporary steel support's precise derock value. The strain change in value fed back each government measure effect in the project emergency .Through gauging the axle strength anchor rod, we judge the adjacent rock loose circle in distortion section already surpassed 4m, so we need to adopt the 6m long steel pipe to grout reinforcement during distort section. In disease management, we utilize surface grouting , increasing the temporary steel support, the addition to invert temporarily, doing the foot steel pipe, increasing the body pipe shed, and so on .Finally we through the tunnel shallow submersion bias section successfully. The paper use the quality detection instrument for quality detection during the tunnel construction process ,and get the appraisal to the quality.This article take the actual project as the object of study, utilizes the research results in project practice and gets a more remarkable economic and social efficiency ,so it has a reference value for the similar project.