Study On Dynamic Response Of The Lining Tunnel System In Saturated Soil Due To Traffic Load

With the rapid development of railway construction and urban rail transportation, public concern about dynamic response and environmental disturbance of the underground tunnel system due to traffic load becomes more and more. Based on Biot’s theory of saturated soil, dynamic response of the lining tunnel system in water-rich area is investigated under the interaction between the liner and outside soil. The studies of this dissertation consist of the following parts.1. The train load is uniformly distributed along the tunnel circle as a moving constant load and the traffic load is simplified as axisymmetric load. The liner is modelled as elastic body. The governing equations of the lining tunnel system are decoupled with Helmholtz potential theory and Fourier transformation. According to the boundary condition and continuity condition, the analytical solutions of dynamic response for the liner and soil are derived in frequency wave-number domain. Then the response in time space domain for the lining tunnel system in saturated soil are obtained by using Fourier inverse transformation. The present method are validated by comparing the solutions with relevant reference. The results show the liner has much effect on dynamic response of the tunnel system. Moreover, some numerical examples and corresponding analysis are made to investigate the influences of the load speed, the ratio of elastic modulus between liner and soil, the interaction parameter between soil skeleton and pore water.2. Subjected to point traffic load, the liner is regarded as Fliigge thin cylindrical shell. Load and dynamic responses of the lining tunnel system are expressed as Fourier series forms by the circumferential modes. Using Helmholtz potential theory and Fourier transformation, the solutions of the lining tunnel system in saturated soil due to vertically moving harmonic point load applied to the tunnel invert are firstly presented on the basis of the boundary condition and continuity condition. Some numerical study are made to investigate the circumferential distribution of dynamic response and the influences of the load speed, initial frequency on dynamic response. The research results show this method can effectively achieve the response of lining tunnel system in saturated soil under non-axisymmetric traffic load. Furthermore, track slab and floating slab, rail are simplified as Euler beam. Using Fourier transformation of convolution integration, the dynamic response of ballastless track lining tunnel system and floating slab track lining tunnel system in saturated soil is calculated under vertical harmonic point load. The results show this method can also be applied to calculate response of these two tunnel system in saturated soil under point load. The effects of track slab, floating slab and rail are discussed in comparison with the dynamic response of lining tunnel system.3. On the basis of previous study, the two-liner-tunnel system in saturated soil is separated into two subsystems:two-liner system and two-cavity system. By means of Fourier series expansion, the harmonic point load and dynamic response decompose into symmetric part and antisymmetric part. The dynamic response of outside soil in two-cavity system can be the response superposition of two single-cavity system. Using the boundary condition and continuity condition on the outer surface of two liner, the dynamic response for side-by-side two-liner-tunnel system and piggy-back two-liner-tunnel system in saturated soil are presented in consideration of the interaction between two tunnels. In comparison with the single-liner-tunnel system, the results show the neighboring tunnel has much influence on the dynamic response. The influence of load frequency and tunnels separation distance are studied too.