| At present,the cement-stabilized materials in China’s high-grade highways are predominantly semi-rigid base.In the practice,there is a problem that the semi-rigid base may crack into pieces.With a dry climate,frequent windblown sand,a large day-night temperature difference and other unfavourable conditions in Gansu Province,the road base has been confronted with more serious challenges.As for the cement-stabilized road base,the related research is mainly oriented to the question of how to prevent or reduce the cracks caused by the shrinkage,which results from the desiccation or the large day-night temperature difference.Based on the trial section of Ying Shuang highway and the current research results,this paper expounds the design method of anti-crack,cement-stabilized,stone-on-stone macadam in a systematic manner,deepens the research into the mechanical principles and the volume shrinkage of anti-crack,cement-stabilized,stone-on-stone macadam,and verifies the laboratory results in the real case of Ying Shuang highway trial section.This paper starts with the mathematical model calculation and laboratory experiment,and determines the range of parameters that are suitable for vibratory compaction.That is to say,the value of static surface pressure is 140 KPa,the vibration amplitude is 1.4mm,the frequency is 35 Hz,and the vibratory compaction is finished within 2min.Taking this result as the basis,this paper proposes a method for compacting the anti-crack,cement-stabilized and stone-on-stone macadam road base.Meanwhile,this paper takes unconfined compressive strength and indirect splitting strength as the evaluation indexes,analyzing the effects of various factors on the anti-crack,cement-stabilized and stone-on-stone macadam,such as the passing rate of the critical mesh size(4.75mm),the amount of cement and the type of aggregate.As is shown by the experiment results,the mechanical property is at its best when the passing rate of 4.75 mm is under 30%.As for the mixture of anti-crack,cement-stabilized and stone-on-stone macadam,the optimum percentage of cement is 4%.In comparison with basalt aggregate,the limestone aggregate is found to have a lower mechanical strength,but is found to be more conducive to the compaction of road base materials.Therefore,this study adopts the limestone aggregate.In comparison with the traditionally-used suspended dense structure of cement-stabilized macadam,the anti-crack,cement-stabilized and stone-on-stone macadam is 30% lower in the rate of the desiccation shrinkage,and is 10% lower in the rate of the shrinkage caused by the temperature difference.It is reveled that the anti-shrinkage performance improves significantly after the anti-crack,cement-stabilized,and stone-on-stone macadam is adoptedas the material of road base.Finally,the research results are applied to the road base of Ying Shuang highway,and the construction of the trial section is completed.By November 2012,the already-completed road base of Ying Shuang highway totaled up to 46.6 km,and the road base surface was covered with geotextile for the purpose of maintenance during the winter.From the winter of 2012 to the winter of 2013,the lowest temperature in the area along the Ying Shuang highway was-9-19℃.In March 2013,Ying Shuang Project Office organized all the participating units to review the quality of the 46.6km already-completed cement-stabilized macadam road base.This activity aimed at finding the cracks,but no large area of desiccation cracks were found.It is indicated that the vibratory compaction method is good in anti-crack property and can basically prevent the formation of cracks in the cement-stabilized macadam road base. |
