Vibration Response Research Of Saturated-Unsaturated Soil Layered Ground Induced By Moving Vehicle

The planning and construction of the ground and underground transportation network has played a pivotal role in driving economic development and urbanization,and it has also provided great convenience for people to travel.However,the dense layout of the transportation network makes more private houses and ancient buildings along the road.The long-term repeated vibration affects the structures along the line to varying degrees of vibration hazards.Perennial vibration and noise pollution affect the physical and mental health of residents along the line.Therefore,environmental vibration caused by traffic load has become a topic of great concern to the academic community and the public.For the actual foundation in nature,due to the existence of groundwater,the soil above the water level is affected by the environment and climate as an unsaturated state,while the soil below the water level is in a fully saturated state.Based on the existing research framework,this paper considers the unsaturated soil above the water level as a solid-liquid-gas three-phase coupled porous medium,and considers the saturated soil as a solid-liquid two-phase coupled porous medium.Biot porous media theory and mixture theory construct differential governing equations for saturated and unsaturated porous media respectively,and use boundary conditions and continuous conditions of the soil interface to perform coupling solutions to analyze the vibration response of the foundation system.On this basis,pavement and car models were added to the top of the foundation to establish a vehicle-pavement-foundation multi-body system analysis model,and an analytical study was made on the coupled vibration response of the entire system.The specific research work is as follows:(1)Regarding the foundation as a half-space formed by layered saturated soil and unsaturated soil,the steady-state vibration of the half-space foundation is studied.By establishing the three-dimensional control equations of two soil media in a cylindrical coordinate system,and using the Hankel integral transformation to solve the control equations coupling,the analytical solutions of each field quantity of the foundation system are obtained.Using numerical examples,the relationship between excitation frequency and amplitude is analyzed,and the influence of soil characteristic parameters on foundation vibration characteristics is studied.(2)On the basis of layered foundations,symbolic functions are used to describe moving loads,and the governing equations are solved through Fourier-Laplace joint transformation.The analytical solutions of each field quantity in the foundation system under the excitation of point source,line source and area source moving load are solved respectively,and the spatial and time domain distribution of each field quantity are given in the numerical example.Relying on the calculation results,the amplitude attenuation law and frequency domain distribution law of the foundation were analyzed,and the influence of the parameters such as the speed of load movement and geometric size was systematically studied.(3)The road surface and cars are further added to the top surface of the laminated foundation to conduct a full-system coupled vibration analysis.Among them,the road surface is simulated by an infinite Euler beam,the roughness of the road surface is described by power spectral density(PSD),and the car is simplified to a two-degree-of-freedom 1/4single-wheel model.The dynamic contact between the car tire and the road surface is performed by an elastic roller model.simulation.By constructing the control equation of the whole system and performing coupling solution,the analytical solution of the field quantity of the whole system is obtained.A systematic study was made on the influence of vehicle speed,road unevenness and tire inflation pressure on vibration response.(4)Extend the single-wheel car model to a nine-degree-of-freedom and three-axis car model,and reflect the load between the axles and wheels of the car by considering the vertical up and down vibration,front and rear pitching vibration,and left and right sway vibrations during the driving of the car transmission,in order to analyze the vehicle's vibration output and the vehicle-road-ground coupled vibration in the full frequency range.In this model,focus on the analysis of the superimposition effect of the multi-point loads generated by the multi-axle and multi-wheel group vehicle on the foundation vibration response,and the frequency distribution is studied.(5)The dynamic signal acquisition system is used to conduct field measurement of ground vibration induced by car driving.The surface vibration signals at each measurement point are collected by sensors,and the vibration time history curve and frequency spectrum curve at each measurement point are analyzed,and the propagation and attenuation law of surface vibration under different driving speeds,as well as frequency distribution characteristics are further analyzed.Using on-site measurement results,the aforementioned theoretical research results were compared and verified.This paper establishes a series of theoretical analysis models from simple single system to complex multi-body system,gradually deepening the vibration source in stages,and systematically analyzes the environmental vibration problems caused by automobile traffic.Through the comparative analysis of actual measurement research and theoretical research,the feasibility of applying theoretical research in practice is promoted,and provides theoretical guidance and scientific basis for the analysis and prediction of environmental vibration problems caused by traffic loads.