Research On Water Pressure Distribution Law Behind The Drainaged Segment Lining In High Water Pressure Railway Tunnel

At present, as the railway tunnel develops rapidly in China, especially as more and more tunnels will pass through mountain areas, there are often faced with high water pressure problems, which has become the key issue in lots of railway tunnel construction, and the problems seems more and more prominent. In addition, as the increasing development of tunnel boring machine method, to give full play of its advantages, fabricated precast segment lining are often used in building the tunnel structure. With the above situation considered, the author proposed the idea of drainage segment lining to solve high water pressure problem. Currently, there are lack of theoretical research and technical support of drainage scheme, water pressure distribution patterns behind the segment lining and flow discharge.Drainage segment lining is a new kind of structure type which is improved from the conventional segment lining, and it could be used in high water pressure tunnel which is constructed by TBM. This paper is based on National Natural Science Foundation of China project—Research on the Load and Mechanics Characteristics of Drainage Segment Lining with High Water Pressure Railway Tunnel, and the object project is based on a high water pressure railway tunnel on XiangPu railway. According to the finite difference method simulation analysis and similar model test, based on continuum fluid-structure interaction analysis model of fractured rock mass, the water pressure behind segment liner and the distribution patterns of water pressure in the rock were studied under various drainage scheme, and the flow discharge under various drainage scheme was compared.The main works and results are as follows:(1) According to theoretical analysis of the seepage field, and receive the formula, use them in the engineering analysis, then the conclusion can be got, including the relationships between the grouting circle and the flow discharge, the flow discharge and the external water pressure on the segment lining, the external water pressure on the grouting circle and the circle radius.(2) Based on the analysis of seepage fields and stress fields double-fields coupled theory at home and abroad, using the principle of the finite difference method, and adapting to the characteristics of high-pressure mountain tunnel, the author proposed the mechanical analysis model which considered the fluid-solid coupling, and set its reasonable boundary conditions.(3) Using finite difference method, the seepage fields and stress fields in rock under different drainage scheme were analysised. including equal drainage area but different drainage hole number, different drainage hole height between two tunnels, different drainage hole height between two segment lining and different water-head line height, then the distribution patterns and the flow discharge of the two-field were analysised.(4) The model test chamber was made, and the geometric similarity ratio is 1:50, the bulk density similar ratio is 1:1, then the similar model test was done. The relationships between water pressure behind the segment lining and the flow discharge were anlysised.