Study Of Initial Support Effect On The Secondary Lining Structure Force Of Deeply-buried Water Conveyance Tumnel

At present,China has built a large number of long distance interbasin water transfer project,such as the South-to-North Water Transfer project,Han jiang-to-Wei he River Diversion project and Water Network project in Shan xi Province and so on.In these water transfer projects,the deeply-buried water conveyance tunnel plays an important role.However,in most of the water conservancy project,the secondary lining structure design does not consider the initial support in the process of tunnel excavation effect on the secondary lining,completely as a safety reserve.It does not match with the engineering practice.The structure section size is too large and the design is too conservative.To some extent,although it can guarantee the safety of the tunnel,it also causes the work of the project increasing and some unnecessary waste.The underlying reason is that there are still many problems in the theory and calculation of the lining structure.In the composite lining,what is the role of the initial support in the tunnel construction,what is the impact on the secondary lining structure,is the main load-bearing structure,of which what is the proportion or safety reserve.These are the problems that trouble the designer in the design process.These problems have become the bottleneck of the design of deeply-buried water conveyance tunnel in our country,which severely restricted the development of water conveyance tunnel design.Therefore,in combination with the practical situation of project,it is necessary to analyze the bearing mechanism of the initial support and the secondary lining structure,and to study the influence of the initial support of the deeply-buried water conveyance tunnel on the stress of the secondary lining structure.In order to solve the above problems,through summarizing the calculation method of the initial support and secondary lining and analysising of the initial support and secondary lining bearing mechanism model,the load release factor analysis method is put forwarded,which is based on finite element analysis method.Using this method,with the typical middle Yellow River Diversion Project in Shanxi province deeply-buried tunnel as the research object,a numerical model is established,simulating the stress of surrounding rock release process in different stage of water conveyance tunnel construction process,analysising the initial support under different load release factor influence on the stress of the secondary lining structure and the field monitoring data,to summary the load ratio of the initial support and the general change rules of the internal force for the secondary lining structure,providing a reference for the optimization design of similar lining section of the deeply-buried water conservancy tunnel.