Advanced Materials Research Vols. 243-249

Abstract: Two types of high modulus asphalt mixtures are introduced. Dynamic modulus and phase angle of these two mixtures are tested with Simple Performance Testing System under different temperatures, loading frequencies and confining pressures. Based on time-temperature superposition principle, dynamic modulus master curves and time-temperature shift factors at reference temperature are obtained using nonlinear square least square regression, and phase angle master curves are constructed utilizing the same time-temperature shift factors. The influence of confining pressure on mechanical properties of high modulus asphalt mixture is discussed.

Abstract: To solve damage issues of asphalt overlay resurfacing old cement pavement, authors put forward ideas of interlayer water breakage, expounded the mechanism of dynamic water pressure, designed a kind of composite specimens, and separately finished the direct shear tests with the samples water immersion and freeze-thaw for the first time in China. Based on the model of water-tire-pavement system, it is concluded that dynamic water pressure rises with vehicle speed, directly 2 power proportional to speed, and the dynamic pressure were identified as 0.25MPa, 0.40MPa, 0.55MPa corresponding to the running speed of 80km/h, 100km/h, 120km/h, respectively. According to direct shear tests with soaked samples, the longer the sample soaked, the more is layer structure vulnerable to damage. Compared with the sample not-soaked, the shear strength respectively reduces by 50% or 64.6%, corresponding to the samples soaked 24h or 48h. With the freezing and thawing sample, direct shear tests show that the roles of the hydrostatic water in layer leads to interlayer structure intension lessening by 58.8% over the natural sample. The results declare that the bond is weakened by dynamic pressure, soaking, freezing and thawing of interlayer water, which will eventually result in overlay structure destroyed.

Abstract: To study the traffic characteristic and axles load spectra of a heavy load expressway, WIM data was collected, axle configuration and vehicles classification was determined. The characteristic of truck traffic monthly distribution and the truck hourly distribution was studied and axle load spectra for major tuck types were developed. The results show that there were more than 30 truck types running on the expressway, the peaks of truck traffic monthly distribution was in April, September and December and the rush hour of the hourly distribution was at midnight. All major axles had a bimodal pattern of load spectra. The second peak of single axle was about 12 to 13 ton, tandem axle 14 to 22 ton and the tridem axle 28 to 32 ton. More than 50% of axles were overloading.

Abstract: Flow-ability of CA mortar is characterized by fluidity, and the effects of the CA mortar fluidity according to water, time, and feeding sequence are studied. Studies have shown that the amount of the used of water affects the fluidity most, in which the suitable amount of water is between 0.23 and 0.28. With the time delay, the flow-ability of CA mortar is reduced. When mixed with SBR latex, the process of decay of the flow-ability is significantly reduced. Feeding sequence has great effect on fresh mixed CA mortar. In the mixing process, to avoid asphalt emulsion and cement dry material in direct contact, the speed of demulsification is reduced, which can effectively increase the flow-ability of CA mortar.

Abstract: A type of high modulus asphalt was prepared by mixing modifier into SBS modified asphalt and used for confecting HMAC-16 high modulus asphalt concrete with finished product of modified asphalt from Liaohe oil field. This paper investigates pavement performance of high modulus asphalt concrete and its practical application in bridge pavement. Results obtained by application in practical project show that the high modulus asphalt concrete is provided with outstanding high-and-low temperature performance and water damage resistance which are suitable for bridge pavement.

Abstract: This paper analyzes the mechanism of geogrid-broken stone pile reinforced sand-gravel cushion soft base strengthening system (GSPS) using finite element based on the substantial project of a expressway in Sichuan province. The calculation results indicate that the GSPS system can significantly improve the vertical displacement (settlement) of subgrade with the vertical displacement around pile decreasing around 15%, and the subgrade displacement tends to be more uniform and smooth. Also, the GSPS system improves the horizontal displacement of subgrade the most compared with the common broken stone-pile, sand cushion and reinforced cushion. The embankment becomes relatively light when it is low, and the main top loads are borne by geogrid-broken stone piles. With the top loads increasing, the loads shift to the soil among piles, and the pile-soil stress ratio increases with the increase of stress level. The test and analysis results show that the value range of pile-soil stress ratio is 1.88~3.40.

Abstract: The double finite cosine integral transform method is exploited to obtain explicit solutions for the natural frequencies and mode shapes of the orthotropic rectangular plate on foundation with four edges free. In the analysis procedure, the classical Kirchhohh orthotropic rectangular plate is considered and the Winkler elastic foundation is utilized to represent the elastic foundation. Because only are the basic dynamic elasticity equations of the orthotropic thin plate on elastic foundation adopted, it is not need prior to select the deformation function arbitrarily. Therefore, the solution developed by present paper is reasonable and theoretical. In order to illuminate the correction of formulations, the numerical results are also presented to comparing with that of the other references.

Abstract: This paper based on the dynamic triaxial tests of completely decomposed granite samples of the Wuhan-Guangzhou passenger line to study the relation of the accumulated residual strain and the load times of completely decomposed granite and cement improved soil, and analyzes whether they meet the dynamic strength and cumulative cyclic deformation indicators and requirements of high-speed railway under vehicles load. High-speed driving when the subgrade generate residual plastic deformation. Residual plastic deformation of the continuous development will inevitably lead to the deterioration of the road, such as cracks, jack mud, uneven subsidence and long-term slow subsidence of the roadbed. Therefore, by studying the dynamic strength and the size of the dynamic stress of different parts of subgrade embankment to determine the appropriate filling parts of filler and control the final dynamic stress level of the roadbed at a reasonable range in order to ensure lines in good condition in the design life.

Abstract: A reasonable design strength standard is of great practical significance for reducing pavement diseases. First, the bottom layer tensile stress of the typical pavement structure in the operating period is calculated using computer program BISAR while the overload、the interface link status and construction variability are all considered. And then the bottom layer tensile stresses of the upper and lower base are checked under truck load during construction. According to the relationship between cleavage strength (90d) and unconfined compressive strength (7d), it is deemed that the appropriate design strength standard should be 2.1MPa~3.5MPa. Finally, combined with the results of the unconfined compressive strength of core samples in the field it is proved that the current design standard is a little high.

Abstract: G212 highway is a primary route from Gansu to Sichuan province. Landslides and debris flows along G212 highway often occurred in Longnan region of Gansu province. According to finite element method of saturated-unsaturated seepage, variation of pore water pressure of saturated-unsaturated slope under transient seepage field was simulated in the cases of rainfall and groundwater and safe factor of the slope stability was obtained, based on Fredlund’s strength theory of unsaturated soil and Bishop’s method. As an example of the Qinyu west landslide, the drainage, guarding face wall and frame structure with pre-stress anchor rod were very effective and feasible for the landslide treatment measures.