Evaluation On Impact Of Construction Sequence To Stability Of Exit Slope Among One Tunnel In Songpan County And Comparative Analysis Of Treatment Measures

After Wenchuan earthquake, the state invested a lot of funds for post-disaster reconstruction. Road reconstruction patency is one of very important jobs. This deformed body is caused by the Construction Sequence to one tunnel in Songpan county which belongs to Wenchuan highway reconstruction project connecting Wen chuan and Songpa. It was located at the inside of road stake of National Highway G213. By a detailed analysis of tunnel construction sequence, it is found that the construction side is not in accordance with the designation at the sequence of construction. The preliminary view is that the construction side of the deformable body is caused by the illegal operation. Therefore, it is very important to do research on excavation sequence.In this paper, the deformed body was taken as the research object. Firstly, on the basis of detailed investigation and research geological environmental conditions of the deformed body, the author adopted site exploration and drilling projects, found out the nature of landslide, the scope, development scale and morphological characteristics. Its formation mechanism and influence factors is studied on the basis of depth analysis of the basic features, metaboly, developmental history of the deformed body. GEO-SLOPE was used to do two-dimensional numerical simulations, focusing on the stability of the slope of under the normal sequence and the actual construction timing. And ultimately, the best control measures were proposed by comparative analysis of slope stability under kinds of reinforcement.The main results and conclusions can be expressed as follows.(1)The deformed body was U-shaped distribution. The slope was mainly composed of colluvium and alluvial material. And the slope could be divided into two deformable zones:A traction area, B secondary deformation zone.(2)The deformed body is the result of the interaction of slope structure (internal factors), artificial excavation and rainfall (external factors). And manual excavation was the dominant factor. Potential failure mode should be creep-cracking of surface soil.(3)In accordance with the design timing of construction, the slope was very steady with all the stability coefficient more than1.15in three conditions. In the actual construction sequence, in working condition Ⅰ, the slope was unstable with the stability coefficient0.98to0.99. Under working conditions Ⅱ and Ⅲ, the stability coefficient obviously decreased. The storm is more obvious than the earthquake on decreasing the stability coefficient.(4) The prevention measures for the deformed body were studied by a comparative way. The combination program of counter-pressure backfill and the framework of anchoring cable-beam was suggested to achieve the purpose of comprehensive treatment.