In order to study the high temperature rheological properties of high modulus asphalt cement (HMAC) and clarify its definition criteria, firstly, three kinds of HMAC binders were prepared with high modulus modifiers and subjected to dynamic shear rheological test (DSR), zero shear viscosity test (ZSV) and multi-stress creep recovery test (MSCR). Based on the tests and analysis, the complex shear modulus (G*), rutting factor (G*/sin d), zero shear viscosity (ZSV) and unrecoverable creep compliance (Jnr) were taken as technical indexes for the performance evaluation of HMAC. Further, through analyzing the consistency of evaluation results of different evaluation indicators and the correlation between evaluation indicators of HMAC binders and HMAC mixtures, the definition criteria of HMAC binder are eventually given. The test results show that the three high modulus modifiers can improve the viscoelastic properties and high temperature properties of the matrix asphalt, but the modification effect is slightly different; the rheological properties index can basically make a consistent evaluation of the high temperature performance of three kinds of HMAC binders, but the correlation degree is different. The dynamic stability (DS) of the mixture is well correlated with G* (60 degrees C, 10 Hz, 0.1%) (refers to the complex shear modulus measured at 60 degrees C, loading frequency 10 Hz and strain level 0.1%), G*/sin delta (76 degrees C, 5 Hz, 0.1%) (refers to the rutting factor measured at 76 degrees C, loading frequency 5 Hz and strain level 0.1%), zero shear viscosity (60 degrees C) and Jnr. 3.2 (76 degrees C) (refers to the unrecoverable creep compliance measured at the stress level of 3.2kpa and the temperature of 76 degrees C), but the correlation of dynamic modulus (E*) with zero shear viscosity (60 degrees C) and Jnr. 3.2 (76 degrees C) is poor. In summary, it is recommended that HMAC binder should meet both G*(60 degrees C, 10 Hz, 0.1%) >= 60.0 kPa and G*/sin d (76 degrees C, 5 Hz, 0.1%) >= 5.0 kPa, and the definition criteria can be as a design basis for HMAC binder. At the same time, it is recommended to use J(nr 3.2) (76 degrees C) to evaluate the high temperature performance of HMAC. (C) 2019 Elsevier Ltd. All rights reserved.
With the establishment and improvement of highway video surveillance system, traffic target recognition has become a key concern technology in the field of transportation. Aiming at the problem that the existing traffic target recognition technology has poor tracking effect on obscured and blurred targets in continuous motion vehicles, an improved Camshift motion vehicle tracking algorithm is proposed, which predicts the possible position of the obscured target in the current frame by Kalman filtering algorithm, and searches for the target in the position neighborhood of the image frame by Camshift algorithm using color information, combining with the multi-vehicle Tracking chain principle to achieve multi-vehicle tracking. The experiments show that this method can track the moving vehicles effectively in real time, and even when the vehicles are obscured in large proportion, the vehicles can still be tracked correctly, which verifies the effectiveness of this method.
Taking the vegetation species diversity of expressways in Shanxi Province as the research object, this paper selects ten cutting slopes in six operational expressways to carry out the field investigation.Under different geographical locations, geological types of green land, green ecological restoration construction technologies, operation time, and other factors, the difference in Shanxi′s vegetation species richness is discussed. Through the investigation and analysis, it can be seen that the vegetation species diversity of expressway is greatly affected by three factors: geographical location, geological type of green land, and green ecological restoration construction technology, and less affected by the operation time. The vegetation species diversity of expressway is optimal in south Shanxi, the second in middle Shanxi, and the poorest in north Shanxi. The vegetation species diversity of the loess slope is better than that of other poor geological slopes. The diversity of slope vegetation species after applying the ecological restoration technology is significantly better than that of applying the traditional hole planting technology.
Various types of accidents occur frequently in the long-steep slope section of the expressway.Focusing on safe driving risks in the long-steep slope section of the expressway, to further strengthen risk control, this paper uses the analytic hierarchy process to sort the weight of the identified risks and determines the specific influencing degree of each kind of risk. According to the weight sorting result, a targeted precise risk control measure is proposed.
To study and evaluate the slow-released snow-melting property and frost resistance of the self-snow-melting asphalt mixture, the theoretical evaluation method was used to study the self-snow-melting pavement with the VPRSalt content of 3%, 5%, and 7%. Based on the snowfall grade model, it was calculated that the sodium chloride precipitation of VPRSalt self-snow-melting asphalt pavement after 12 h of the snowfall only accounted for 0.57%, 0.55%, and 0.50% of the original storage, indicating that the material has good slow release performance. Using the model to estimate the frost-resistance time and temperature showed that under the condition of light snow, increasing the content of the self-snow-melting material of the asphalt pavement from 3% to 7%, the frost-resistance temperature was lower, the frost-resistance time was longer, and the frost-resistance effect was better. Evaluating the road performance of the VPRSalt self-snow-melting asphalt mixture with the increase of the VPRSalt content from 3% to 7%, the dynamic stability, the low-temperature maximum bending strain, residual strength ratio of freeze-thaw splitting, and residual stability gradually decreased, however, they still met the requirements of Technical Specification for Construction of Highway Asphalt Pavements.
