Study On The Building Technology Of Highway Tunnels In The Mountainous Areas

Because of complicated terrain and geological conditions in western China, a great number of tunnel engineering may occur during the highway construction in mountainous areas. In order to improve the building technology of highway tunnels in mountainous areas, also, to enrich and to develop highway tunnel design and construction methods of China, this thesis systematically studied the design and construction technology of highway tunnels in mountainous areas of Yunnan Province from such aspects as the characteristics and values of wall rock pressure, tunnel structure-type selection, design technology, construction technology, dynamic feedback design and information construction etc by means of site investigation, numerical modeling and model test. The main research results are as follows:(1)The wall rock pressure of single tunnel, multi-arch tunnel, and neighborhood tunnel, and deformation pressure of deep tunnel are studied. For single tunnel, the author offered horizontal pressure of the wall rock of the deep single tunnel, wall rock pressure of shallow tunnel when the ground is nearly horizontal and the calculation methods of wall rock pressure of shallow tunnel when ground is inclined. For multiple-arch tunnel, the author puts forward the calculation method of wall rock pressures of the deep multiple-arch tunnels, the dividing value between deep and shallow tunnels, the wall rock pressure of the shallow multiple-arch tunnels and the wall rock pressure of multiple-arch tunnels with bias pressure. For neighborhood tunnel, the author put forward the calculation methods of wall rock pressure of the deep neighborhood tunnels, horizontal loads at the both sides of retaining structures of deep neighborhood tunnels, the uniform vertical pressure and horizontal wall rock pressure on the both sides. As for the aspect of deformation pressure of deep tunnels, the author studied calculation problems including deformation pressure calculation of single tunnel, deformation pressure of tunnel secondary lining and wall rock deformation pressure above tunnel retaining structure. On the basis of studying the classification of wall rock of highway tunnels in mountainous areas with complicated geological conditions, the methods of determining physical and mechanical parameters are proposed.(2)After analyzing the structure selection of highway tunnels in mountainous areas, the author thought that whether it is separated tunnel, multiple-arch tunnel or neighborhood tunnel, it has its own advantages. Therefore, which one is the best can not be lumped together. These tunnels all have their own applicable conditions, so, their advantages and disadvantages can be discussed only based on these conditions. For example, separated tunnel is used when considering engineering cost; multiple-arch tunnel or neighborhood tunnel is used with environmental protection, occupied area, connecting difficulty as first choice. When hesitating to choose multiple-arch tunnel or neighborhood tunnel, if considering less occupied area, very complex topography, bridge tunnel connection, landscape design, technology innovation, geological forecast, and environmental protection, multiple-arch tunnel is superior to neighborhood tunnel; if considering engineering cost, construction difficulty, neighborhood tunnel is optimal. At the same time, the problems of structure selection on highway tunnels under special geological conditions are also discussed in the thesis.(3)For design problems of highway tunnels in the mountainous areas, the design technologies of separated tunnel, multiple-arch tunnel and neighborhood tunnel are studied respectively. In the design of separated tunnel, the author studied cavity structure of tunnel, supporting structure and types, pre-reinforcement parameters, initial supporting measures, secondary lining parameters and reservation deformation parameters. In the design of multi-arch tunnel, the author studied the structure of multi-arch tunnel, the design of center pillar, water-resistance and abstraction of water, lining supporting parameters, and connection pattern outside of the tunnel entrance. Also, the author carried out a comparison about various lining cross-sections. In the design of neighborhood tunnel, the author studied the strategy for selecting supporting system, carried out similar model test in the case of bias pressure and differential height, and simulated the displacements and stresses of different construction stages in the case of shallow location, bias pressure and different height by two- and three-dimensional numerical modeling taking the Pingnian tunnel as an example.(4)It is thought that the key design of multi-arch tunnel is the design of center pillar, including the type selections of center pillar, construction plan, technologies of water-resistance and abstraction of water, etc. Design of center pillar on multiple-arch tunnel should be selected based on its merits according to analyzing systematically the terrain and geological conditions of tunnel, connection conditions of tunnel and a comprehensive analysis of conditions including straight integral type center pillar, hollow straight center pillar, straight layer center pillar, flexural integral type center pillar, hollow flexural center pillar, and three layer flexural center pillar. At the same time, if conditions permit, three layers curved middle wall multi-arch highway tunnel should be more considered.(5)The construction technology of separated tunnel, multiple-arch tunnel, and neighborhood tunnel in mountainous areas are studied. For separated tunnel, the author studied construction technology of tunnel entrance, tunnel excavation, primary supporting, secondary lining construction, and put forward construction methods of separated tunnel in poor geologic section. For multiple-arch tunnel, the author contrasted and analyzed the typical construction methods of multiple-arch tunnel. Also, tunnel entrance, construction of open cut tunnel, pre-reinforcement, tunneling and primary supporting of middle drift, center pillar construction, excavation and primary supporting of the main tunnel, secondary lining and the multi-arch tunnel construction under special and poor geological conditions are studied. For neighborhood tunnel construction, the author put forward the principles and countermeasures for selecting construction measures on neighborhood tunnels, the determination method for a suitable distance of adjacent tunnels face, the time determination method of supporting system, the excavation technology and blast-controlling technology and the reinforcement technology of middle rock walls.(6) As for dynamic feedback design and information construction of highway tunnels in mountainous areas with complicated geological conditions, the author presented executive routine of information construction, means of data acquisition, methods of data processing and information feedback, and implement outline and process of the dynamic feedback design and information construction.