Applied Mechanics and Materials Vols. 178-181

Abstract: In order to analyses affection to thermal conductivity from various factors, such as: coarse aggregate, mortar ratio, sand ratio, water cement ratio, fly ash and air content, thermal conductivity of a series of concrete specimens were determined based on thermal conductivity meter. The results showed that: coarse aggregate, mortar ratio and gas content is the main factor affecting concrete thermal conductivity. Meanwhile, water-cement ratio, sand ratio and fly ash had few effects on the thermal conductivity. In addition, a certain formula to predict thermal conductivity of concrete was proposed.

Abstract: To reflect the real risk situation of mountainous rural highway and find out security risks, it is essential to ensure road safety with setting reasonable and effective security facilities in road-side dangerous sections. Based on SPA theory, establish the risk rating as the target layer and traffic characteristics, cross-section of the road, horizontal and vertical alignment as the criterion level, the Set Pair Analysis Model (SPAM) of mountainous rural highway road-side risk rating evaluation which contains ten key indicators realizes quantitative evaluation of risk rating on road-side risk. The model which is applied to practical engineering considers local materials as principle, proposes road-side protection facilities type and design parameters for different risk levels which is suitable for mountainous rural highway. Applications in Chengde mountainous rural highway show that evaluation results of SPAM model are objective and reasonable, it is a new method of comprehensive evaluation of the complex system for mountainous rural highway.

Abstract: In order to study viscoelastic properties of asphalt mixture, an advanced Shear Rheometer is used. The continuous dynamic frequency scanning test is carried out, which can get full-temperature-full-frequency master curve of asphalt mixture by the time-temperature equivalence principle. The CAM model acts as the rheological model for studying viscoelastic properties of asphalt mixture, because CAM model’s parameters have clear physical meaning. Then viscoelastic properties of asphalt mixture are studied basing on the four equations of CAM model in the full-temperature-full-frequency range.

Abstract: Wuhan-Guangzhou passenger special line is the most important backbone of China high speed railway net. The line span is 968 km, among of them; roadbed is 388 km, occupied 40.1% of the total line. Due to the rigorous residual settlement of the roadbed, the CFG (Cement Flayash Gravel) pile is used as the composite foundation to enforce the intensity of roadbed and reduce the post-settlement. The paper studies on CFG pile composite foundation at the Wuhan experimental section, using the finite element numerical simulate the interaction of the pile and pile surrounding soil under the permanent load conditions. The results show that the stimulation model has the more accordance with the actual observation results. The residual settlement comes from the soil layer is bigger than the pile length.

Abstract: In the construction of an overpass transversal to an existing electric railway, when the overpass pier is door-shaped, and, when the clearance height from the bottom of the door-shaped pier cap beam to the contact wire electrified body is too small to use steel beam or I-beam for holding the formwork and meet the safety need prescribed by the Ministry of Railways, an innovative construction method was employed, in which D-type steel beams, originally used for railway track reinforcement, was lifted to get across the contact wire and the catenary from above with a gap more than 33.8cm, resting on the top surface of temporary buttress, and letting stocky horizontal beams hold the formwork of cap beam, so as not to affect the normal operation of the existing electric railway. This innovative technique has been granted patent for invention by the State Intellectual Property Office.

Abstract: Based on the overhaul structure of actual asphalt pavement, establishes the finite element model and analyses the shear stress in the state of overload, longitudinal slope and contact coefficient. The result is that the load and the gradient of longitudinal slope larger, the influence of rutting more seriously. The growth of shear stress is larger which brought by adding load on steep longitudinal slope than that of adding on longitudinal slope. The contact coefficient of interlayer α larger the maximum shear stress larger, on the contrary, the contact coefficient of interlayer α smaller the maximum shear stress smaller.

Abstract: The strict control standards for post-construction settlement of high-speed railway require high accuracy of settlement calculation. Harmonizing the contradiction that settlement calculation theory lags far behind the engineering practice, the computational method of additional stress of foundation urgently needs improvement. For Geosynthetic Reinforced Pile-Supported (GRPS) embankment, as the stress caused by the load acting on soil between piles is an essential part of the whole, the computed results of additional stress of foundation largely depend on the load magnitude and load distribution form of soil between piles. Starting with the mechanical behavior of GRPS embankment, this paper analyzes the classic assumptions of soil arch form and their computation theory of load acting on soil between piles, and then deduces the distribution function of parabolic load, which can provide basis for further research on calculating the additional stress.

Abstract: Considering the joint loading-transfer effect, a 3-D finite element model which consists of thirty full-scale slabs is established. Making the aircraft loads act on different positions and calculating their vertical displacements. The results indicate that the loading area is compressive and the regions far away from loading area are tensile and that the vertical displacement curves change dramatically when aircraft wheels act on different locations.

Abstract: HMA dynamic modulus is one of key inputs to the Mechanistic-Empirical Pavement Design Guide. In order to analyze and evaluate bearing capacity of asphalt concrete pavement and to determinate the rules of pavement deterioration of modulus of asphalt layer under repeated wheel load and ambient, temperature correction for HMA is applied to the modulus so as to compare them with the same temperature. In order to get temperature correction coefficients for HMS moduli, a method of temperature correction for HMA moduli was put forward. In this method, the specimen of asphalt mixture or HMA cores from in-situ pavements were tested by Superpave Simple Performance Tester(SPT), or falling weight deflection(FWD) was tested on the site of in-situ pavements. The correlation between HMA dynamic modulus and temperature was regressed, and then dynamic modulus regression model was put forward. Results show that exponential function was fitted to the data to determine and adjust the modulus to a reference temperature, the recommendation regression equation can reflect the features of asphalt mixture at the reference temperature.

Abstract: Friction is the extremely important factor when considering the interaction between the shock wave and the tunnel wall. But so far, the impact of wall friction on the shock wave is mainly measured by experimental methods. This paper mainly discusses the effect of wall friction on the shock wave attenuation, without considering roughness, roughness elements, the viscosity of air, and the complex relationship between them; the numerical simulation calculation model is established with DYNA calculation software; the influence law of friction coefficient on tunnel shock wave propagation and attenuation is given based on friction coefficient between air medium and tunnel wall, so as to provide guidance to mining, reduce the impact of tunnel explosion shock wave on personnel and equipment and provide a design basis for shaft safety works.