Applied Mechanics and Materials Vols. 97-98

Abstract: The slab track is a new sort of track structure, which has been widely used in high-speed rail and special line for passenger. However, the ballastless track structure design theory is still not perfect and can not meet the requirements of current high-speed rail and passenger line ballastless track. In this paper, composite beam method is used to calculate the deflection of the track plate and in this way the vertical supporting stress distribution of the track plate can be gotten which set a basis for the follow-up study of the dynamic stress distribution in the subgrade. Slab track plate’s bearing stress under moving load is analyzed through Matlab program. By calculation and analysis, it is found that the deflection of track plate and the rail in the double-point-supported finite beam model refers to the rate of spring coefficient of the fastener and the mortar.The supporting stress of the rail plate is inversely proportional to the supporting stress of the rail. The two boundary conditions of that model ,namely, setting the end of the model in the seams of the track plate or not , have little effect on the results. We can use the supporting stress of the track plates on state 1to get the distribution of the supporting stress in the track plate when bogies pass. Also, when the dynamic load magnification factor is 1.2, the track plate supporting stress of CRST I & CRST II-plate non-ballasted structure is around 40kPa.

Abstract: The method of fracture mechanics is used to analyse the fatigue crack propagation of cold-recycled base material in this paper. The suitable fracture mechanics formula and parameters are choosen and then we deduce the fatigue life forecast equation.After that we annlyse the method of determineing parameters and give the axample.The conclusion is gained through comparing with the database obtained from the experiment .It is more reasonable to forecast the fatigue life of cold-recycled base material with crack based on the method of fracture mechanics.

Abstract: For high-speed railway subgrade settlement, there was usually a big difference between calculated and measured value. Studying the stresses distribution under embankment, giving more accurate simplified method，was a approach to improve the accuracy of calculated settlement. The stresses distribution under embankment were studied through tests on experimental embankment segment, geotechnical centrifuge model tests, and numerical analysis and calculation. Studies showed that the measured stresses distribution was curve, the stresses under the embankment centre were highest, under the vicinity of shoulder the stresses changed smoothly, the stresses was above zero at toe of the side slope.

Abstract: In this paper, the initial asphalt content is estimated by the hot-mixed asphalt mixture rapid calculation method in condition that we have no information about the similar project, and five asphalt content are selected with regarding the estimated asphalt content as the middle value, then carries on the Marshall test. The optimuml asphalt content is very accurate by the calculation and experimental method, the method greatly improved the test efficiency.

Abstract: Subgrade resilience modulus is an important mechanical parameter in pavement design. It will directly influence the design result of pavement structure. Using BISAR3 of SHELL design method, the impacts of subgrade resilience modulus on pavement surface deflection, base and subbase bottom tensile stress, surface layer bottom tensile stress of the heavy load asphalt pavement structure were analyzed. And the influencing laws were analyzed, too. The results show that the mechanical and deforming characteristics of heavy load asphalt pavement were influnced significantly by subgrade resilience modulus. With the increasing of subgrade resilience modulus, the pavement surface deflection, base bottom tensile stress would significantly decrease, and fatigue life would be improved.

Abstract: Post-construction settlement is one of the main issues in high grade railway construction in saline areas. The efective solution to the problem is to find the post-construction settlement law for the guidance to the design and construction based on the field monitored data. After analyzing the large quantities of monitored data from the second double line of Lanzhou-Xinjiang Railway in saline areas, a new model is put forward. The standard hyperbolic model, the modified hyperbolic model and exponential model were applied to the forecasting settlements based on the same monitored data to test the presented new model. By comparing fitting, forecasting accuracy and stability of different methods, show that the new model has a high prediction accuracy and good stability, and the forecasting data agree well with the monitored data. The new model presents a new method for analysis and prediction of settlement, and it is found to be a good reference to post-construction settlement of embankment in saline areas.

Abstract: The current prediction methods of foundation settlement have biggish error under the condition of lesser foundation settlement observational datum. Aim at the localization of present prediction methods and the virtues of Support Vector Machine arithmetic, the method of predicting soft soil foundation settlement based on Least Square Support Vector Machine (LS-SVM) was proposed in this paper and compared with the neural network method and curve fitting method. The research results show that this proposed method is feasible and effective for predicting soft soil foundation settlement. Least Square Support Vector Machine provides a more advanced method than these conventional methods for predicting foundation settlement.

Abstract: In order to evaluate pavement dynamic responses accurately under truck loading, the full-scale asphalt pavement accelerated loading facility (ALF) was used. 10 strain gauges and 2 soil pressure cells were installed; temperature sensors were also installed in the different depth of the HMA layer. Pavement response was measured under real traffic load with ALF. The measured pavement responses are compared between the pavement sections to evaluate the effects of various experimental factors, such as axle load, speed, et al. Dynamic strain at the bottom of HMA layer and vertical compressive stress on the top of the subgrade were examined in the full-scale testing road, the regression models between dynamic response and axle load, dynamic response and speed were put forward respectively. Studies show that there is not only tensile strain but also compressive strain in the dynamic response, and the strain response is in the station of tension and compression alternation. Under the intermediate temperature, the strain response at the bottom of the asphalt layer is increased linearly with the increase of axle load and the vertical compressive stresses at the top of the subgrade is also increased with the increase of axle load. Speed has a great effect on strain response at the bottom of HMA layer, and has little effect on vertical compressive stress, it affects the loading duration of stress only. The destroy for the pavement by low speed and heavy load is more serious than that is normal.

Abstract: It has been commonly used normal distribution to describe the fatigue life of asphalt concrete. Because of the variability of the material itself and environmental conditions for test, experimental fatigue life datas obtained show a large discrete. Through a large number of laboratory tests and optimization of the strong representation of the data source, this paper verified distribution of the fatigue life of asphalt concrete in statistical in the use of two-parameter Weibull distribution theory and obtained fatigue life equation by regression under different failure probability.The results showed that: Weibull distribution theory can be used to describe asphalt concrete fatigue life distribution under the complicated conditions in a multi-factor.