Study On Water Pressure Of Tunnel Structural System In Rich Water Area And Calculating Boundary In Seepage Field

In the tunnel engineering, seepage discharge and water pressure affect each other. Water pressure in seepage field has a disadvantage on tunnel construction period and operation period, and it caused tunnel disease. Studying on water pressure of tunnel structural system in rich water area and calculating boundary in seepage field, firstly, related theories of tunnel in seepage field and control measures of tunnel seepage are understood. Secondly, according to theories, axisymmetric solution and equivalent and axisymmetric solution are extended to horseshoe shaped tunnel. Then the axisymmetric solution that considers respectively of primary support and secondary lining of more adapted to composite lining is derived. Thirdly, calculating boundary in seepage field that water head height is 10 times of section height is studied. From studying theoretical formula, control measures of tunnel seepage and calculating boundary, so water pressure of tunnel structural system in rich water area is researched. The last but not least, summarizing water pressure of different control measures of tunnel seepage, comparing and analyzing 3 kinds of axisymmetric solution, putting forward distribution proportion between primary supporting and secondary lining of water pressure, and normal computation and back calculating of water pressure using in engineering are explored.The paper based on the tunnel project which is the new built-up named Chengkun railway that is from Miyi to Panzhihua tunnel project which is called Ranjiawan, according to the above steps, did research on water pressure of tunnel structural system in rich water area and calculating boundary in seepage field,and the main research contents and drew conclusion as follows:(l)The runnel of surrounding rock which is homogeneous in seepage field calculation can use axisymmetric solution and conformal mapping theory. According to different hypothesis, it can be obtained 3 kinds of axisymmetric solution extending to horseshoe shaped tunnel.(2)Under the whole draining lining, according to axisymmetric solution and equivalent and axisymmetric solution which are assumed by single shell lining, and the axisymmetric solution that considers respectively of primary support and secondary lining of more adapted to composite lining is derived. Analyzing 3 kinds of axisymmetric solution that obtains the factors of affecting water pressure and seepage discharge, it includes that lining thickness and its permeability coefficient, grouting cycle thickness and its permeability coefficient, permeability coefficient of surrounding rock and location of ground water.(3) Through calculating different boundary in seepage field about the first main stress of inverted arch, water pressure of foot of wall, displacement of vault and inverted arch and water pressure of that foot of wall around surrounding rick, it can be compared with the mechanical properties of the above. It is summarized that calculating boundary is 3-4.5 times of widen of tunnel under that boundary is plugging and 3-3.5 times of widen of tunnel under that boundary is draining.(4)It is studied on the change of water pressure and seepage discharge in different control measures of seepage of tunnel structural system in rich water area. The result is that changing permeability coefficient of primary support, thickness of secondary lining and grouting cycle have not effect on water pressure of tunnel structural system under the whole plugging linging, and that decreasing permeability coefficient of lining, increasing thickness of secondary lining and grouting cycle lead to increasing water pressure of lining and decreasing seepage discharge under whole draining lining. In this condition, the tendency of 3 kinds of axisymmetric solution is the same of numerical solution. The seepage error of axisymmetric solution and the axisymmetric solution that considers respectively of primary support and secondary lining are about 15%, and water pressure error of them are 10%, The seepage error of equivalent an axisymmetric solution is about 5%, and water pressure error of it is 8%.(5)Extending the axisymmetric solution that considers respectively of primary support and secondary lining to practical engineering. Making full use of this formula to derive the proportion of water pressure and verifying it by numerical simulation. Otherwise, by the normal computation and the back calculating with reduction factor of water pressure, it is convenient to adapt designed water pressure during construction period in time.