| Subject to the conditions of terrain，longitudinal slope sections inevitably exit in thehighway route. Especially in the construction of western highways, longitudinal slopesections are obviously seen everywhere because of numerous hills. Vehicles, influencedby slope, shall slow down on the longitudinal slope sections of road, which differ fromthe driving state on the flat slope sections. And with frequent brakes and starts, asphaltpavement of longitudinal slope sections is more likely to be damaged. However, presently,our country has not set up related regulations aimed at asphalt pavement of longitudinalslope sections. Combined with the project of Bureau of Transport of Gansu Province[GJG (research)2012(03)]Key Technology Research on Asphalt Pavement of HighwayLongitudinal Slope Sections in Loess Area, and with the pavement structure of the longsteep slope sections, Leixi Highway, Gansu, the author furthers studies on the mid-layerin asphalt pavement of longitudinal slope sections, including stress analysis, gradation,material composition and pavement performance, in order that mixtures’ high-temperature stability can be improved.Firstly, based on a survey of the damage effect of the asphalt pavement inlongitudinal slope sections, Shizhong freeway, the paper analyzes and specifies thedamage types appearing in mid-layer of longitudinal slope sections, which give priorityto rutting damage. The survey is undertaken by Xie Tingting, a member of research group.Taking the pavement structure of Leixi Highway as a sample and analyzing the shearingstress through Bisar3.0, the author obtains the spatial distribution pattern of maximumshearing stress. Meanwhile, the paper also analyzes the influence of some factorsincluding slope, depth, horizontal load coefficient and axle load coefficient, etc. on themaximum shearing stress in mid-layer.Secondly, the author probes into the study from two aspects, aimed at improving thehigh-temperature stability in mid-layer. As for cementing materials, the paper analyzeshigh–low temperature performance, temperature sensitivity, aging and rheology, etc. oftwo types of composite modified asphalts (different dosage level of SBS with rock asphaltand SBS+TLA) through routine experiments and SHRP experiments. Considering allperformances analysis, the dosage level of two natural asphalts (rock asphalt and TLA)has been initially cleared up. As for gradation, it specifies the standard of coarse and fineaggregate with4.75mm being demarcation. And coarse aggregate are progressively filled on the basis of particle interference. Meanwhile, through compacted density experiment,composition proportion of coarse aggregate has been clarified on the principle of coarseaggregate being most tightly packed. Dispersible uniformity of fine aggregate is hard tobe controlled; therefore, the gradation of fine aggregate is specified by the Super-20rangeput forward by Lin Xiuxian instead of by progressive filling compacted densityexperiment. Next, the gradation is modified by using Bailey parameters.Finally, the paper does research into the influence of different gradation andcementing materials on pavement performance through related experiments. Besides,through the comparing analysis of their indexes, it concludes the relationship betweenhigh-low temperature index of two composite modified asphalts (SBS with rock asphaltand SBS+TLA) and mixtures’high-lowtemperatureperformance, andproposes theindex,which can represent the cementing materials’ high-low performance of two asphalts.Combined the climate features of mentioned highways, cementing materials performancewith pavement performance, the author specifies the optimum dosage proportion of twocomposite modified asphalts and their advantages and disadvantages at the optimum. |
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