Dynamic Analysis Of Subway Load On Horizontal Support Piles Of Foundation Pit

In recent years,with the increasing congestion of urban traffic,morning and evening peaks occur almost daily.In order to meet the travel needs of citizens and alleviate the pressure of urban transportation,many cities have begun to vigorously develop the subway business.At present,China’s subway transportation has entered a state of vigorous development.The subway network of the old first-tier cities is almost all over the entire urban area.The emerging first-tier cities are gradually improve the subway lines.Because of the underground environmental conditions,many subways lines have to be adjacent or even pass through building,so it is inevitable that a question will arise: will the dynamic loads generated when the subway is operating affect the safety of existing buildings? If this kind of adverse reaction occurs,it will bring unpredictable consequences to people’s lives and property safety,so it is very necessary to analyze the dynamic response of the building under the subway dynamic load.In this paper,the method of numerical simulation will be used to analyze the dynamic response of the foundation pit horizontal support pile under subway load to verify whether the safety of the component is sufficient.Through control variables,a comparative analysis of single factors is made and a series of anti-vibration measures are proposed.The main contents of the study are as follows:1.By referring to a large number of documents and related research results,having learned about the classification and hazards of vibration,related mechanical problems under subway load,the current research status of domestic and foreign scholars on subway vibration load and the study of the impact of subway load on existing buildings;2.The mechanism of train vibration is analysed from the two factors of wheel and track irregularity and the current method of describing track irregularity is mainly described.According to the generation mechanism of train vibration,the wheel-rail system is simplified to a two-degree of freedom vehicle model and the vibration equation of the simplified model and the mathematical expression of train vibration load are given.Finally,the simulink simulation software was used to simulate and solve the two-degree of freedom earthquake equation and the excitation force loads of train speeds of 30km/h,50km/h,70km/h were obtained;3.The wave equation of elastic wave is given,according to the propagation characteristics of elastic body wave and elastic surface wave,the two waves are simplified on the basis of elastic wave wave equation and their respective characteristic wave equations are obtained.The energy of the vibration wave source generated by the main human factors such as engineering construction and transportation through the soil medium is mainly the combination of the body wave and the rayleigh wave.The law of decay with distance and the formula of attenuation amplitude proposed by Yang Xianjian and China’s “Code for Basic Design of Power Machines;4.Based on the large-scale display dynamic analysis software ANSYS/LS-DYNA,the integral coupling finite element model for foundation pit horizontal support pile-subway tunnel-soil is established and the relevant model materials and element types are analyzed and selected to obtain the overall structure.The dynamic response of the whole structure under subway load is obtained.5.According to the anti-vibration at the vibration source,the anti-vibration of the propagation path and the anti-vibration principle at the building,based on the stiffness of the under-rail gasket,the damping of the under-rail gasket,the stiffness of the underlay of the track plate,the damping of the underlay of the track plate,the depth of the vibration isolation groove,the width of the vibration isolation groove,the filling materials of the vibration isolation groove,the materials and the cross section of the horizontal support pile nine factors,a numerical analysis model for tunnel-soil-foundation pit horizontal support piles with different parameters under subway load was established.The equivalent stress time-history curve of the supporting piles at the same position in each low is selected as a comparison and the effects of various design parameters on the vibration reduction and vibration isolation effects are qualitatively analyzed.The content and results of the study can provide a reference for vibration reduction similar to this project.