Research On Structural Optimization And Section Design Of Lining Structure Of Trench Type High Fill Loess Open Cut Tunnel Under Load Reduction

At present,high fill open-cut tunnel is commonly used in the modern traffic route design structure,its mechanical properties and structural design there are many problems still need to be discussed.Most scholars at home and abroad have achieved some research results in the distribution law of earth pressure and the design of open-cut tunnel around the high fill open-cut tunnel and its load shedding structure.However,there are few reports on the changes of internal force and lining thickness of high fill open-cut tunnel based on the different structure types of EPS board load reduction.Therefore,by means of numerical simulation and model test,this paper optimize the structure and load shedding structure of high fill open-cut tunnel,study the internal force of open-cut tunnel and its load shedding structure of different structure types and the change rule of lining thickness,reveal the load shedding characteristics of EPS board,and give the optimal structure type of open-cut tunnel and its load shedding structure.Finally,the results of model test and numerical simulation are consistent with each other,which verifies the correctness of finite element method.The main research contents and innovations of this paper are as follows:(1)Uniaxial compression test was carried out on EPS boards with different densities,and mechanical properties of EPS boards with density of 12kg/m~3?15kg/m~3?20kg/m~3?30kg/m~3 are obtain,which provides basis for numerical simulation and model test parameters.(2)Using ANSYS software to establish the original high fill open-cut tunnel structure model,from the mechanical properties of EPS board materials and Principle of load shedding.The variation rules of internal force and lining thickness of each part of the original open-cut tunnel before and after load reduction were studied,and the optimal load shedding height of EPS board with density of 12kg/m3 and thickness of 2m was determined.(3)Structure of the original open-cut tunnel position(arch,arch shoulder,hance,wall type,and inverted arch)optimization,analysis of 50m filling load under the action of different structural type of open-cut tunnel structure internal force and cross section lining thickness,get the optimal structure of high fill open-cut tunnel,then the best load shedding thickness and density of the EPS board is spread in different structure of the ceiling of open-cut tunnel for load shedding analysis,get the optimal structure of load shedding open-cut tunnel.(4)Through the model test,the internal force of the original open-cut tunnel and the optimized open-cut tunnel before and after load shedding was tested.The test results of the change rule of the internal force of the original open-cut tunnel with the height of filling before and after load shedding were compared with the numerical simulation results,which verified the correctness of the numerical simulation method.The comparison between the internal force change rule of the open-cut tunnel before and after load shedding verifies the effectiveness of load reduction of EPS board.The comparison between the optimized and original open-cut tunnel verifies the necessity of open-cut tunnel structure optimization.