Applied Mechanics and Materials Vols. 178-181

Abstract: In this paper, authors analyzed the semi-rigid road base asphalt pavement of towns and studied the optimum design methods of it, combining characteristics of town roads, considering natural conditions, vehicle axle,materialsupply,construction techniques, maintenance, transportation and so on, referring to design experiences of asphalt pavement in Tian Jin area, through indoor and outdoor experiments, applying math methods. In addition,optimum pavement structure function and calculating methods is given out, asphalt pavement structure adapt to Tian Jin area is recommended and CAD program is developed.

Abstract: In order to ensure the quality of the reconstruction project of freeway as well as the traffic efficiency without breaking down the traffic, it is crucially important to arrange the work zone length alternately by sub-ways and subsections. The simulation method of transportation is adopted for Microscopic of the transportation situation under various length of work zone. Based on the results of the simulation, the stability, efficiency and safety of traffic flow are evaluated and analyzed comprehensively. The balance point among these three factors is determinated by the method of fuzzy comprehensive evaluation. Combined with the project cost, construction cost saving and other factors. to get the reasonable construction segment length reference value. Finally, G4 freeway (Beijing to Hong Kong and Macao) is selected as a case study.

Abstract: With the large-scale speed-up of the railway, the dynamic track stabilizer will play an important role on the track overhauling and railroading of new line in our country. Bogie is one of the major critical components of the dynamic track stabilizer; its vibrating characteristic will affect the vibrating characteristic of the dynamic track stabilizer directly. The method of numerical simulate was used, based on the spectral density of the track irregularities, the time domain loads of the track irregularities were gained. Then the vibrating characteristics of the dynamic track stabilizer bogie under the excitation of the track irregularities were analyzed on the bases of the ANSYS/LS-DYNA. And the lateral, dilation, ups and downs, nod, swing and anti-rolling vibrating characteristics of the bogie on the six degree of freedom were obtained. The analysis results of this paper will provide foundation for the research on the stationarity and security of the dynamic track stabilizer.

Abstract: To explore the relationships between the performances and microstructures of modified asphalt, in the tests, one kind of basic asphalt、two kinds of modifiers and four kinds of modifiers content were selected to prepare modified asphalt. The SBS modified asphalt performances such as softening point, viscosity, Rutting Factor G*/sinδ and the corresponding microstructures with different shearing time were analyzed. The results show that different modifiers have different modification effects on the asphalt，but the change trends of performances and microstructures with the modifier content and shearing time are basically the same. It is also found that there is a good relationship between microstructure and macro performance, the average area of the modifier is closely related to the softening point, total area (or area percentage) and the shape factor of the modifier are suitable to reflect the mechanical behavior of modified asphalts.

Abstract: As the social economy and urbanization develop rapidly, a new high-speed railway city construction is undergoing. Urban designing theories that lack of research and practice leads to immature designs of high-speed railway stations. Based on urban design cases currently undertaken and theories and practices from home and abroad, this thesis analyzes the specialty of urban design of the high-speed railway stations. This thesis points out the significance to propose a scientific and reasonable strategy of developing areas and producing energy, and points out the significance of pattern of land-using on this sort of design. In terms of the specialty of the development and design of high-speed railway stations, this thesis offers some valuable insights into future research and practice.

Abstract: Goaf critical depth is used to describe the influence of buried goaf on upper structures, that is to say, if the goaf burial depth is less than the goaf critical depth, the goaf must be emphatically treated, and if the burial depth is greater than the critical depth, but less than one and half of the critical depth, the goaf also need to be treated, and if the burial depth is greater than one and half of the critical depth, the goaf need no treatment. Nowadays, mechanic balance method has been using to calculate the goaf critical depth, which considers the upper rock as the loose structure, and the destroy plane is vertical. Based on the discussion of critical depth calculation methods, the critical depth calculation method thinking of the cohesive strength of the part upper rock was put toward. The method was applied to the goaf treatment engineering of Chengtang Freeway of Hebei province, and was proved by the monitor results. The critical depth calculation method can reduce the engineering quantity of goaf treatment.

Abstract: In order to analyze the effect of dynamic calculation parameters to subgrade deformation, cross-section in the Shanghai-Nanjing high-speed railway is chosen and the numerical simulation calculation method is applied. Through numerical calculation of 121 kinds of conditions combining dynamic shear modulus and dynamic damping ratio, the dynamic elastic deformation of point A and dynamic partial stress of bottom layer of foundation bed were studied. It shows that the maximum dynamic elastic deformation of point A reduces with dynamic shear modulus and dynamic damping ratio increasing. Moreover, the value of average dynamic partial stress augments with dynamic shear modulus increasing, and reduces along with the increase of dynamic damping ratio. Using nonlinear fitting method of constructing three polynomial surface equations, the function of total deformation with dynamic calculation parameters is obtained.

Abstract: Numerical simulation of ground penetrating radar is an effective way of analyzing and studying high frequency electromagnetic wave propagation rules in the underground media. In this paper, Finite-Difference Time-Domain (FDTD) method is used for numerical simulation to form radar records reflection profile about road disease such as loose disease. The purpose is to study and sum up the radar wave propagation rules and reflection signal characters in this diseases media, in order to provide reliable theory support for road maintenance and evaluation.

Abstract: The main function of fastener was achieved by elastic bar. The traditional method for the study of fatigue stress, strain analysis, which was not reflected the true situation, because the elastic bar in the work with other members of the contact surface between the mutual movement of tiny was created, i.e. fretting. The shear stress（ ）, relative displacement（ ） and two of the product（ ） of elastic bar was calculated out by applying Coulomb friction model of nonlinear contact theory of simulation of elastic bar and the surrounding contact element. Theoretical analysis was shown that, if the fretting wear in fatigue fracture was played a major role, it should be located in a section of the and of the value of the biggest point of attachment. Fastener fatigue tests was shown that, a fracture was found at the tail of elastic bar and baffle contact, which was between the value and value of the maximum point and closer to the value for maximum point. Crack was created because of fretting wear of tail of elastic bar and baffle, then the pollution source was formatted, and crack was propagated under the repeated effect, and the fracture of elastic bar was created eventually. The theoretical analysis of elastic bar of fretting wear was shown correctly by the fatigue test, and the improved design of elastic bar for a improving fatigue life was provided scientifly.

Abstract: The varying laws of the longitudinal grade at the partial any point on the vertical curve in the course of the freeway’s profile design were discussed via the analytical formulas calculation, and the minimum longitudinal gradient and the length of roads which cannot meet the current requirements were found out, then application effect of vertical curves with the large radius was explored. On this condition, some countermeasures and suggestions were provided for the reasonable design of the vertical curves.