Study On The Compositive Construction Technology Of The Two-line Passenger Transportation Special Line Tunnel Which Passes Through The Water Bearing、Satured And Powder Fine Sand Layer

The lanzhou-chongqing railway taoshuping tunnel in process is the two-linepassenger transportation special line tunnel which passes through the water bearing、satured and powder fine sand layer, it is the typical large section tunnel which passesthrough the weak layer. For the condition of the layer is bad, its stability is bad, thesedimentation deformation of the tunnel in the construction process is large, the tunnelis apt to collapse, the time is short, on the background of the construction of the largesection tunnel, the paper used some methods, such as theoretical analysis、numericalsimulation and field monitoring and so on,analysed the construction technology of thetunnel which passed throughthe water bearing、satured and powder fine sand layer. The study of the paper came tothe following conclusions:(1) To the construction of the taoshuping large section tunnel which passes throughthe water bearing、satured and powder fine sand layer, combined with the existingengineering construction technologys, the homologous construction schemes were putforward; combined with the tunnel3#slop well work area main tunnel engineeringconstruction practical conditions, the construction schemes which were put forwaredwere analysed and intercompared, one random scheme of both construction schemeswhich were “three steps inverted arch method” and “double hole at the bottom forwardmethod” could be adopted by the tunnel, which was determined preliminary.(2)To both construction schemes which were “three steps inverted arch method” and “double hole at the bottom forward method” which could be adopted by the tunnelwhich passed through the water bearing、satured and powder fine sand layer, thenumerical simulation were used, both construction schemes were analysed andintercompared in the aspect of the vault sedimentation、the stability of the surroundingrock and the stability of the early support structure and so on, the “double hole at thebottom forward method” construction scheme was advised to use prior.(3)Combined with taoshuping tunnel3#slop well work area main tunnelengineering construction practical conditions, the optimization to the sequence and theanalysis to the stability were done to taoshuping tunnel3#slop well work area maintunnel which adopted “double hole at the bottom forward method” to construct, theinfluence which the distances among the palm faces of every part hole palm face in the“double hole at the bottom forward method”; the analysis of the study indicated: theincrease of the distance between the two holes at the bottom is good for the stability ofthe tunnel, but the decrease of the distance between two holes on the top is good for thestability of the tunnel, the decrease of the distance between the higher level and thelower level is good for the stability of the tunnel, so, within the limits which is allowedby the construction conditions, the distance between the higher level and the lower levelis advised to be shorter, the distance between the two holes at the bottom is advised tobe bigger, but the distance between two holes on the top is advised to be shorter.(4) The field monitoring work was done to taoshuping tunnel3#slop well workarea main tunnel following the construction, and the comparison study between themonitoring and theoretical analysis was done, the field monitoring work and thecomparison study between the monitoring and theoretical analysis indicated: the“double hole at the bottom forward method” which was advised by the numericalsimulation to use was suitable for the construction in the water bearing、satured andpowder fine sand layer, the shape deformation and the internal force of the tunnelsupporting structure changed steadily, and tended to stabilize at last.