Coal tar bearing emulsions were used in the Netherlands as binder in anti-skid surfaces for runways because of their perfect adhesion and fuel resistance properties. They are however toxic and will not be allowed anymore after 2010. Therefore alternatives need to be developed. As one of the alternatives, two types of two-component epoxy modified bitumen have been investigated by means of direct tensile tests (DTT), relaxation tests (RT) and dynamic shear rheometer (DSR) tests. The effect of the curing temperature on the strength development of the epoxy modified bitumen was tested. The results show that the tensile strength increases with increasing curing time and temperature. DTT and RT results indicate that this new epoxy modified bitumen has a much higher tensile strength, cures faster than a bitumen emulsion as a binder. Furthermore, it shows a good stress relaxation even at lower temperatures. The curing speed and the ultimate tensile strength after full curing can be easily adjusted. The DSR results show that the complex modulus of this epoxy modified binder is less susceptible to changes in temperature. The results also suggest that this epoxy modified bitumen has better anti-crack properties at lower temperature and less permanent deformation than bituminous binders at higher temperatures. All these results shows that this type of two-component epoxy modified bitumen can be promising as a binder in anti-skid layers.
Gussasphalt is widely used in steel deck pavement in cold regions; thus, it should have good low-temperature performance. A method for evaluating the low-temperature performance of gussasphalt is presented in this paper. Low-temperature bending, bending creep, and splitting tests were used to study the performance of different types of gussasphalt. The sensitivity and correlation between low-temperature indices obtained from three methods were compared and analyzed with sensitivity factors and the grey relational coefficient, respectively, and the low-temperature evaluation index and standard of gussasphalt in cold regions were determined. Flow, penetration at 50°C, low-temperature bending, and bending fatigue tests of the trabeculae were carried out after secondary mixing of gussasphalt asphalt concrete. Degradation of the material performance after different storage times was studied. Finally, taking the strain energy density as the main control index and considering the fluidity, the high-temperature performance, fatigue characteristics, technical requirements for storage, and mixing time of gussasphalt in cold weather after two mixing procedures are discussed.
Shear fatigue damage to the waterproof cohesive layer has not received enough attention in bridge deck pavement design. Meanwhile, there is less theoretical basis for the design of a waterproof cohesive layer. In this study, direct shear and shear fatigue tests were used to compare the shear strength and fatigue performance of waterproof adhesive materials under different disposal schemes for a cement slab surface, bonding materials, and spreading schemes, and the recommended optimal dosage of waterproof adhesive material for the bridge deck is given. Based on the shear fatigue tests results of indoor waterproof adhesive materials, an equation for prediction fatigue at 15 °C was established and temperature correction was applied. Based on these results, we propose a waterproof cohesive layer design method for bridge deck pavement with interlayer shear damage as the design index. The life expectancy of the shear damage between the decks was calculated for a real bridge deck. These results provide scientific guidance for design of a waterproof cohesive layer in a bridge deck, which can effectively extend the service life of a bridge deck.
Abstract. In order to solve the problem of water-rich loess tunnel in construction process, the paper based on the idea of underground water environmental balance, use the Kuniaki Sato empirical formula and underground runoff modulus to build correlation function, get the permeability coefficient. Then we combine the engineering practice condition of the Qiaoyuan tunnel, use the duplex pipe grouting to reinforce the water-rich loess tunnel, and evaluate the grouting effect. Results show that there are a great lot of obvious grouting veins on tunnel face, and the bedding is clear. There are not bleeding phenomenon on tunnel face. The surrounding rock is stable, no such phenomenon occurred as collapse, instability, gushing water or mud, etc. The soil strength has increase dramatically, and the permeability has reduced significantly. The permeability coefficient of grouting soil meets the requirements of underground water environmental balance.
Most of the widely used Automatic Incident Detection (AID) methods are based on the basic principle of the California Algorithms which detects incidents by comparing the difference of macro traffic parameters between upstream and downstream. However, these AID algorithms cannot perform well under lowvolume condition due to many incidents under low-volume don't cause significant changes on traffic conditions. To improve the incident detection under low-volume condition, the paper proposes a new detection method based on Automatic Vehicle Identification (AVI) technique by using high-resolution cameras. First, the paper introduces the basic theory and characteristics of Low-volume Incidents (LVIs) detection by using high-resolution cameras, analyzes the time-space relationship of vehicles passing different detection sections, designs a elimination method for the false plate identification, and proposes a new AID method for LVIs. Second, the paper studies how the main influence factors, including the detection devices density, accuracy rate of AVI and flow level impact the new AID model's performance. Finally, simulation cases are studied to examine the performance of the new AID model. The case study shows that the new AID model can produce satisfied detection results even with very low detection devices density.
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