Applied Mechanics and Materials Vols. 178-181

Abstract: Foamed asphalt can be used to stabilize reclaimed asphalt pavement materials at environment temperature. In this paper, the effect of cement on the performance properties of foam asphalt recycled mixture were evaluated by laboratory tests, including indirect tensile strength (ITS) test, moisture resistance test, rutting test and low temperature bending test. The test results find cement can improve the ITS, moisture resistance and rutting resistance of foam asphalt recycled mixture. However, the higher cement content can decrease the low temperature bending failure strain. Therefore, it is recommended the optimal cement content for foam asphalt recycled mixture is between 1.5% and 2.5%.

Abstract: Brookfield Viscometer, Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) are employed to analyze properties of rubber asphalt and TOR rubber asphalt after water aging. Through simulating, the influences of parameter changes of water on the performances of asphalts after aging were studied. The results show that the PH value and sodium chloride content of water affects the aging properties of asphalt, and as the parameter changes, the high temperature performance of TOR rubber asphalt are better than rubber asphalt. DSR and BBR tests reveal that the higher the acidity (or the lower PH value) and the sodium chloride content of water are, the more seriously rubber asphalt and TOR rubber asphalt age in water aging; the lower the temperature is, the larger the S value and the smaller the m value become, and the worse the low temperature performance and dissipation of temperature stress of rubber asphalt and TOR rubber asphalt get.

Abstract: Tamping homework is the important means of railway ballasted track maintenance meanwhile it is a complicated and changeable process. The compaction degree is an important parameter for discrimination which is a basis to estimate the effect of tamping homework. The author adopted Bond Ball and Bounding Sphere methods based on the spherical particles in EDEM software. Modeling and simulation research for real railway ballasted particles are conducted in this article. The author puts forward that the change of ballasted track shear strength is the main basis of discrimination criterion for the compactness of the track. Based on discrete element theory, the main work is to establish a rigid-flexible coupling dynamic model of tamping tines and sleeper and ballasted track, and according to this model, the dynamic response of the granular particles under tamping load is calculated. Based on this model, tamping frequency change from 15 to 60 HZ scope with the steps of 5 HZ, the track of the compaction degree of different change can be researched. The research shows the discrete element method is an effective method for solving the numerical simulation of railway ballast of trackbed tamping. The compactness of trackbed is best when tamping frequency changes near 35 HZ.

Abstract: In order to study the influence of reinforcement on the distribution of dynamic deviator stress along the depth of subgrade, reinforced and unreinforced subgrade of graded-broken-stone-based asphalt concrete pavement under traffic loading was modeled by implicit dynamic FEM. Analytical results show that reinforcement can improve the vertical compressive stress distribution, and decrease shear stress transmitted to the surface of subgrade. The deviator stress on the upper part of reinforced subgrade is reduced distinctly, which is one of the key factors that can cause residual deformation. Therefore, reinforcement can restrain the development of residual deformation of subgrade induced by traffic loading.

Abstract: The load transfer property of embankment fills, cushion, pile (or with cap) and foundation soils are complicated in a piled embankment. In this paper, the vertical load effects of pile and foundation soils at the bottom of embankment were analyzed with consideration of the interaction of each component. The arching effect of embankment fills and the pile-soil interaction were respectively formulated, and then, with continuous displacements and stresses at the bottom of embankment, a calculation method of pile-soil stress ratio was presented. In addition, the influence of the setting of cushion and geosynthetic was analyzed. The present method could definite the load sharing between pile and soil, and may be applied in the engineering design of embankment supported by spares piles.

Abstract: In order to study the shearing stress of asphalt surface on lean concrete base, first of all, three–dimension finite element model of the asphalt pavement is established. The main objectives of the paper are investigated. One is calculation for shearing stress of asphalt surface in transverse contraction joint of lean concrete base, and the other is analysis for relationship between load stress of asphalt surface and parameters, such as thickness, modulus. The results show that maximum shearing stress, which is caused by load, is evident in asphalt surface which is located in transverse contraction joint of lean concrete base of asphalt pavement. Maximum shearing stress decrease, decrease, decrease and increase respectively with increase of the surface’s modulus, the surface’s thickness, base’s thickness and ratio of base’s modulus to foundation’s modulus.

Abstract: Using pavement thickness layered system computational theories and methods that current design criteria proposed, according to the result of the calculating example, this paper analyzed the influence of different soil base and the base stiffness of highway asphalt pavement for base thickness, and pointed out that thickness of pavement base decreased with increase of the soil base and the base stiffness. Therefore, optimum selecting fillers in constructing road bed beside the upper part of the roadbed, strengthening the subgrade and compacting by layer, to improve the mechanical properties of subgrade. Meanwhile, it has important significance in obtaining the obvious economic effect on decreasing thickness of pavement structure by properly using base material of high stiffness. Besides, this result indicate that the base course underside stresses increased with the base stiffness, therefore, the base course underside stresses should be checked, to ensure the corresponding the tensile strength of base material.

Abstract: Based on dynamic tri-axial test at low temperature, deformation behavior of ice is studied under stepped axial cyclic loading. Time history curves of residual strain of ice are investigated under different negative temperatures and frequencies. Conclusions can be drawn as follows: dynamic residual strain rate increases with the increasing of stress ratio and frequency, while decreases with the decreasing of temperature. According to test data, power function is brought forward to fit the relation between stress ratio, negative temperature, frequency and dynamic residual strain rate. Then, the effect of fitting parameters by temperature and frequency was investigated.

Abstract: Unity and change are the basic principles of highway landscape design. Based on the investigation of highway revegetation, new concept of revegetation design was given. Bad roadside landscape should be sheltered by green belts, and beautiful roadside landscape should be divulged or showed by locally eliminating the green belts, and maximum length of green belts with single pattern should be limited for preventing drivers from dozing. Based on the theory of dynamic vision, this paper presents the formulas for computing the stake numbers of setting or eliminating the green belts according to the requirements of landscape design, and the formulas for computing the maximum length of green belts with single pattern. The results are helpful to the highway roadside and median green belts design.

Abstract: Aiming at discussing the behavior of piled embankment under seismic excitations, the numerical analysis model is built by employing ADINA. The interaction of embankment backfill with piles and subsoil is considered. And Coulomb contact pairs based on penalty algorithm is adopted to simulate the contact behavior between pile and soil. Through the varieties of relative displacement and acceleration of embankment structure acted by earthquake loads are analyzed, the weakness of structure is marked and corresponding design suggestion is proposed. It reveals that the displacement and acceleration response of embankment vary non-monotonically, and the peak value of acceleration response of pile firstly increases and then decreases with height of pile, and one of displacement response relative to pile bottom firstly increases and then decreases as well.