| Within about 70% of the territory of Pakistan,the maximum air temperature exceeds 40°C in about 100 days of the year,and the maximum air temperature in some areas even exceeds 50°C,which is an extremely thermal climate.Under the influence of high temperature,the asphalt pavement has been exposing to the extremely high temperatures for long times,even the maximum pavement surface temperature could exceed 75°C.Highway bears 90% passenger volume and 96% freight volume in Pakistan,so the task of traffic is particularly onerous.Lack of supervision from local governments led to the serious situation of overloading of freight vehicles,the wheel pressure of heavy-duty truck is close to 1.0 MPa,and the maximum is over 1.2 MPa.Under the combined effect of double adverse conditions,extremely thermal climate and prominent heavy-load traffic,Pakistan has long been plagued by serious rut disease of asphalt pavements,as well as the similar problems encountered in the N5 highway reconstruction project,funded by China.The appearance of rutting would not only shorten the service life of asphalt pavement,but also affect the driving comfort.It will also bring great hidden danger to traffic safety,even cause social adverse effects and huge economic losses.Therefore,solving the serious rutting problems in Pakistan not only has important practical significance and value,but also could improve the effectiveness of Chinese foreign aid.To Middle East and Africa,which have similar climate conditions and traffic conditions,also have important reference significance and guiding significance.This thesis relied on the N5 highway reconstruction project,firstly conducted the investigation and analysis of the factors,which cause the rut diseases,the common and serious root cause of rutting diseases in Pakistan is that the actual performance of the pavement asphalt concrete does not achieve the performance requirements of extremely thermal climate and heavy load conditions,resulting in the shear instability of the rut,then discusses and proposes solutions to the rutting diseases.Secondly,based on the EPC system network and sensing technology,a real-time online continuous temperature monitoring system for asphalt pavement was established,multiple regression analysis was performed on the monitoring data for consecutive years,and a pavement surface temperature prediction model was proposed,combined with high temperature and heavy-load conditions on the road surface.Put forward the performance index requirements of cementing material and mixtures.Thirdly,aiming at improving the anti-rutting performance of the mixtures,a variety of mixture gradation design concepts and advantages are merged.Using the hypothesis of volume filling assumption,a rapid design method for gradation dense gradation is proposed.The asphalt mixtures designed using this method achieves a satisfactory in the actual performance.1.Combined with the internal temperature distribution law of the pavement,the characteristics of traffic load conditions and design of the pavement structure,the requirements for the performance indicators of asphalt materials and asphalt concrete are proposed.2.Reasonably selecting asphalt materials and admixtures,developing mix ratio design and optimization,improving material composition design,and with strict construction process control and quality management,in order to ensure that the pavement performance of the physical project achieve the requirements of the indicators.3.When the air temperature exceeds the design temperature,operations and management measures on road,such as vehicles restricted and water cooling are adopted to prevent pavement surface disasters from occurring. |
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