Study On The Cyclic Loading Test Equipment Of Ballast Bed And Research On Relative Characteristics Of Ballast Bed

The track structure of ballasted track bed is an important part of modern railway system,and its reliability will be important influence on the railway train operation safety.A ballast bed geometry deformation and degradation is one of the important indicators of its reliability.So study on geometry deformation and deterioration mechanism of the ballast bed has become an important research topic in engineering application of ballast bed.With increasing transport capacity and the rapid development of modern transportation and railway transportation to the direction of high speed and heavy load,the increasing demand of the reliability of ballast bed is necessary.At the same time,a ballast bed filling ballast is composed of a large number of different shapes,physical and geometrical features of different gravel,theoretical research for the study of ballast bed has become difficult to achieve.Therefore,it has important academic significance and engineering application value to carry out cyclic loading test on ballast bed with geometric distortion and degradation mechanism and to evaluate its reliability further.This research is funded by the National Natural Science Fund Project "Research on dynamic response and deterioration mechanism with ballast bed under high-speed cyclic loading from a micro standpoint"(No.51565021)and the Provincial Research Fund Project "Research on dynamic response with high-speed railway ballast bed under external out-load"(No.2015FB132).The study will be started from the research on the key technology of test equipment and test methods,and carried out research around the geometric deformation of a ballast bed under cyclic loading and degradation mechanism.The main research contents and conclusions of this paper are showed as follows.1.Based on discrete element theory and combined with the analysis of the contact mechanics behavior of poly-hedra ballast particles,contact analysis of mechanical behavior of polyhedrin ballast granules are implemented in this paper.A measuring method and the test equipment for getting the granular ballast track bed compactness parameter are presented and implemented in the paper.It is implemented by getting through the change of contact strength measurement between sleeper bottom contact plate and ballast particles.2.A kind of indoor test equipment platform of granular ballast track bed for cyclic loading and tamping is presented and implemented in this paper.And it can be used as follows that,for example,studying on deterioration mechanism of granular ballast bed deformation under cyclic loading,the physical and mechanical properties of track ballast bed,the vibration characteristics and dynamic response characteristics of ballast.The following key technologies are realized in this paper.According to the study need of ballast bed cyclic loading test,especially considering the repeatability test cyclic loading test and multi-station conversion requirements,a mobile loading vehicle device and a cyclic loading working device based on the order loading are presented in this paper.A new technical method is proposed in this paper that it is implemented the load of moving transportation loading simulation through test equipment established.According to the design method of the distributed parallel loop,the control of the actuator in the working device of cyclic loading is carried out.A hydraulic control loop to achieve cyclic loading is presented in this paper.Through the special design,the actuator of cycle loading device can achieve the load in the 30 tons range of the stepless pressure change,and achieve the frequency of cyclic loading in the range from 0 to 10 hertz.Through the analysis of moving loads characteristics of bulk particle materials,a method to obtain the dynamic characteristics parameters of ballast track ballast bed and supporting technical scheme under cyclic loading are presented in this paper.3.A test method that aimed for full life cycle of ballast bed is presented in this paper based on accelerated life theory and the orthogonal experiment design.The relevant research work of accelerated life test according to the vibration characteristics of a granular ballast bed in the whole life cycle is carried out on the model of cyclic loading test established.Track vibration test the range of train speed from 60 to 160 kilometers per hour is carried out to get the dynamic characteristic parameters for vibration acceleration of ballast bed of vertical and horizontal and vertical directions of the three respectively.Using regression analysis method based on statistical principle,the nonlinear regression equation is obtained to characterize the correlation between vibration characteristic parameters and train speed.By means of time domain,frequency domain and theoretical calculation,the results of this test model are compared with the results of field test and the theoretical analysis results.And it draws the following conclusions in this paper.?The results of the model test and the results of field test and theoretical analysis are compared at low driving speed state.The changing trend of train ballast bed vibration acceleration has a certain consistency in the time domain,frequency domain.So this shows that the test equipment and test methods used have high reliability.?Through the analysis to the vertical and horizontal and longitudinal ballast bed acceleration spectrum at different driving speed of train,the main vibration acceleration frequency is from 10 to 180 hertz.?The results of regression analysis show that the fitting curve between the vertical vibration acceleration and track driving speed is close to the logarithmic curve model test data.And the fitting curve between the horizontal vibration acceleration and track driving speed is close to the power function curve model test data4.The relevant research work of accelerated life test according to the settlement characteristics of granular ballast bed in the whole life cycle is carried out on the model of cyclic loading test established.The results show the following conclusions.?Track bed settlement increment and track vibration acceleration is approximately proportional to the square,with the increase of the traffic speed track bed settlement increment increases.?The relation between track bed settlement increment and the contact strength that is from the bottom of sleeper and the top of ballast bed close to the exponential curve growth.?This paper reveals that the relationship between the track accumulative settlement and the number of cyclic loading accords with logarithm curve by regression analysis method.?This paper establishes model of initial variable ballast subsidence of roadbed based on the number of cyclic loading N for settlement calculation and gets a granular ballast bed life prediction model on the basis of the model established.It provides a theoretical basis for scientific management of the maintenance of ballast bed.The innovation points in this paper show the following conclusions.? A measuring method and the test equipment for getting the granular ballast track bed compactness parameter are presented and implemented in this paper based on discrete element theory and combined with the analysis of the contact mechanics behavior of poly-hedra ballast particles.?A kind of indoor test equipment platform of granular ballast track bed for cyclic loading and tamping is presented and implemented in this paper.It is mainly included cyclic loading working device,mobile loading vehicle and hydraulic control circuit based on the distributed control aimed for effective cyclic loading.?Track vibration test the range of train speed from 60 to 160 kilometers per hour is carried out.And the results of regression analysis show that the fitting curve between the vertical vibration acceleration and track driving speed is close to the logarithmic curve model test data.And the fitting curve between the horizontal vibration acceleration and track driving speed is close to the power function curve model test data.Through the analysis to the vertical and horizontal and longitudinal ballast bed acceleration spectrum at different driving speed of train,the main vibration acceleration frequency is from 10 to 180 hertz.?The relevant research work of accelerated life test according to the settlement characteristics of granular ballast bed in the whole life cycle is carried out on the model of cyclic loading test established.It established model of initial variable ballast subsidence of track bed based on the number of cyclic loading N for settlement calculation and gets a granular ballast bed life prediction model on the basis of the model established.It provided a theoretical basis for scientific management of the maintenance of ballast bed.