Study On The Engineering Characteristics And Construction Technologies Of Large Cross-sectional And Water-bountiful Loess Tunnel

The construction items of tunnel at loess area increase rapidly as "the development campaign of the western regions" process. In our nation, we have not mastered the action principal, the deformation law and theory basis of wall rock of loessial large cross-sectional tunnel between preliminary bracing, so the build of mostly loessial tunnels still adopts traditional construction at the present time although there are many disadvantages, for example, the procedure is very heavy and complicated, the program schedule is very length. What's more, the construction at the deep, water-rich and brittle loessial area is a difficult technical problem in the field of tunnel, accordingly universal judgements and fruits of analysis is few.In paper, we analyze the universal construction techniques of national loessial tunnels, and compared with the common techniques adopted during the construction of ZHENGZHOU-XIAN passenger transport tunnels. The excavate construction technique and construction mechanical effect of "seven excavate work" were also introduced in detail here, in the example of concrete construction process of ZHANGMAO tunnel, the preliminary investigation fruits are as following:(1) Establish the construction techniques of water-full and loessial ZHANGMAO tunnel. At first we analyze the international and national investigation actuality of water-full loessial, and the mechanical mechanism and laws of wall rocks in tunnel. Then, we comparted the concrete geologic actuality of ZHENGZHOU-XIAN with universal construction techniques. At last, we established the construction techniques of ZHANGMAO tunnel.(2) Analyze the feasibility of our construction techniques. We analyzed the working procedure, construction essentials and the sedimentation effect of vault. Then we assured that this technique can decrease cost, shorten time and improve working efficiency. At last we confirmed the feasibility of this techniques.(3) We tested the sedimentation effect of vault and constringency of walls after this construction, then explained in mechanical theory at the assistance of track monitoring system. These forces are as follows: force between wall rocks and preliminary bracing, force between preliminary bracing and liner, the passive forces of steel arch and so on. During which, the forces between wall rocks and preliminary bracing, preliminary bracing and liner, and the passive forces of steel arch in the preliminary suggested the forces of liner after the construction; the passive forces of the steel arch in the second liner suggested the passive forces of concrete. After those analysis, we found out the crack positions and the working procedures needs to be improved, then work out the advice on improvement of the preliminary bracing and the second liner.(4) Here we investigated the force characteristic of the deformation of water-full loessial tunnel, then bring forward the applicable demand, detailed construction outlines and technological advantages of "seven excavate work", at last work out the accordingly monitoring project, content and monitoring effect analysis, which ensured the favorably accomplishment of constructions at the deep, water-full and frail area. This work achieved the national advanced level of tunnel construction, which bring strength supervises to fieldwork, and ravel out many technological difficulties during the construction of large cross-sectional loessial tunnel, and provided valuable references to future similar constructions.