| Due to the exponential expansion of urban population and construction,land resources are increasingly limited.To address this problem,lots of cities are vigorously pursuing the development of underground spaces.As the cornerstone of urban transportation,subways play a vital role in reducing urban congestion.However,the vibration generated during subway operations inevitably has a negative impact on adjacent buildings and residents.The elastic wave generated by the subway train on the track is transmitted to the surrounding soil through the tunnel lining,radiating outward through the ground and ultimately reaching the building foundation,causing the building to vibrate.The dynamic interaction between the tunnel,soil,and surface foundation significantly impacts the vibration level of adjacent buildings caused by subways.Furthermore,changes in groundwater levels can alter the moisture content of soil around the subway,changing the fluctuation law of the ground and affecting the dynamic coupling characteristics of the ground and building foundations.Therefore,it is imperative to introduce an unsaturated ground model to examine the influence of moisture content changes on the vibration response of the ground and foundation.The main research work of this paper is as follows:(1)The dynamic coupling response of the tunnel lining-layered ground system under subway loads is investigated.A three-dimensional vibration model of train-track-tunnel lining-layered ground is established based on wave function and Fourier transform theories.The tunnel is simulated as an elastic hollow cylinder,and the ground is simulated as a layered isotropic elastic solid.The model considers wheel-rail irregularity and reflects the multiple scattering effects between the tunnel and the ground surface.The dynamic response of the ground generated by subway trains under different working conditions is analyzed.The research indicates that the soft soil layer on the ground surface can significantly amplify the surface vibration response generated by subways.(2)A three-dimensional coupling analytical model of tunnel lining-layered ground-surface foundation is established.Using the Fourier series and applying artificial boundary conditions around the surface foundation,the solution of the three-dimensional rectangular foundation wave field is derived.The undetermined coefficients in the foundation are solved by the Fourier transform and the orthogonality of trigonometric functions.This model can describe the entire process of elastic wave propagation from the vibration source(tunnel)to the vibration receiver(building foundation).The results show that the dynamic interaction between the tunnel,soil,and surface foundation causes the vertical compliance of the foundation to peak at the resonance frequency of the system,and at the same time magnifies the vertical displacement of the surface outside the foundation area,which has a significant influence on the distribution of the ground wave field.(3)A three-dimensional coupling analytical model of the unsaturated ground-surface foundation is established.The unsaturated ground is considered as a three-phase medium composed of soil skeleton,pore water,and air.The dynamic governing equation of the unsaturated ground is established based on the continuum theory,and the soil-water characteristic curve of the ground is calculated by the V-G model.Four kinds of body waves(P1,P2,P3,and S waves)in the ground are described by the wave function method.The undetermined coefficients in the potential function are solved by the surface boundary conditions and the inter-layer continuity conditions.The results show that the dynamic characteristics of the coupling system can be affected only when the ground is close to saturation.When the ground reaches the quasi-saturation state,the dynamic deflection of the foundation decreases with the increase of saturation.(4)A field test was conducted to investigate the vibration response of the upper foundation and adjacent buildings of a subway station belonging to the Hangzhou Metro Line 1.The study aimed to evaluate the vibration levels generated by the subway operation,and the practicability of the analytical solution was verified by combining the calculation results with the tests.The tests showed that the peak value of the vibration acceleration in the basement of the building during subway operation was 0.08 m/s~2,and that the vibrational energy of each floor was primarily distributed in the 30 Hz to 60 Hz range.Moreover,the vibration acceleration tends to decay as the building height increases. |
