| Reflection crack is one of the main harmful forms of semi-rigid base asphalt pavement,especially in the hilly area of East Sichuan.Because of the high temperature,heavy rainfall with long duration in summer,the harmful problems relating to the reflection crack is more prominent in this area.In order to reduce the risk of early damages of semi-rigid base asphalt pavement,the rigid and flexible compound base asphalt pavement is introduced.The transition layer of graded crushed stone is added between the cement stabilized macadam base and the asphalt layer,which will restrain the reflection cracks and strengthen the drainage to realize the target of prolonging the service life of asphalt pavement.However,graded broken stone is a discrete material,and its strength and stiffness are not as good as cement stabilized macadam or even less than cement stabilized gravel,which results the structural performance of rigid and flexible compound base asphalt pavement is significantly weaker than that of traditional semi-rigid asphalt pavement.In view of this,papers carried out the systematic studies on two aspects of the material road performance of graded crushed stone and the structural mechanical properties of rigid and flexible compound base asphalt pavement by combining with the construction of Suiguang Expressway.The main work and achievements were as follows:1)According to the results of the research on the influence of the maximum particle size of graded crushed stone on its performance characteristics,it was confirmed that the maximum particle size of transitional grained crushed stone applied 26.5mm,and basing on the influence of the molding method of graded crushed stone indoor specimen on the gradation attenuation property and performance indexes,it was determined that the vibration table method was adopted as the forming method to evaluate the integration property of coarse aggregate of graded crushed stone.Basing on this,the optimized partial asphalt mixture gradation design theory was applyed to the design graded crush stone compound.The relevant parameter determination and performance evaluation were carryed out,basing on the integrated volume indexes according to the graded crushed stone compound determined by the general gradation design method(Taibol method,variable i method,change k method)and asphalt mixture gradation design theory(SAC,VS and Sperpave method),as well as regulate the recommended graded.Basing on the multi-stage interlock theory and the purpose of obtaining the transition grade aggregate composition of the supporting engineering in accordance with the actual situation of material yard,the skeleton formation test of coarse aggregate and fine aggregate filling test were carryed out to determine the proportion of coarse and fine aggregate,as well as combined with the indoor test and theoretical calculation,and the main factors affecting the control index of graded crushed stone mixture were analyzed.2)The three-axle test discrete element method was applyed,basing on the analysis of the stress-strain relationship of crushed stone skeleton and the impacts on the graded broke stone rebound modulus from confining pressure and deviatoric stress,in order to evaluate the performance of coarse aggregate skeleton of graded crushed stone.It revealed the nonlinear properties of graded crushed stone and discussed the main influencing factors of water permeability coefficient of graded crushed stone basing on the indoor seepage test.The prediction formula of water permeability coefficient of graded crushed stone was fited.Finally,the composition of graded crushed stone designed by gradation design theory was prioritize to select by combining with virtual triaxial test,CBR test and indoor water seepage test.The design method,grading compound range and evaluation indexes of graded crushed stone were put forward.It could be concluded that the mixture volume design method based on multi-point bracing skeleton state and multi-stage embed gradation design method could determine the composition of graded crushed stone with better performance.3)Taking the dynamic response test section of asphalt pavement as the carrier,three kinds of pavement surfaces(1 kinds of semi-rigid asphalt pavement,2 kinds of rigid and flexible composite base asphalt pavement)were tested by applying FWD and Beckman beam method.The dynamic and static deflection of layered pavement was analyzed.The deflection distribution of asphalt pavement under dynamic and static loads and the deformation characteristics of asphalt pavement during construction were analyzed.However,the Beckman beam method and FWD method are different in testing data,in which the reliability and adaptability of FWD data are higher.Basing on the test results of dynamic deflection basin and combining with the purpose of improving the precision of pavement layer modulus inversion,the layer modulus values of each structure layer for three structures asphalt pavemen were inverted by applying the traditional inversion method and the layer by layer inversion method.The adaptability of the two methods to different pavement structure types was comparatively studied,which concluded that the pavement layer modulus could reflect the properties of pavement structure and composition material comprehensively.The layer by layer inversion modulus method could improve the reliability of inversion structure layer modulus to some extent.4)Considering that the relativity between the theoretical calculation method of equivalent resilience modulus of asphalt pavement structure and the measured results in the field was not good,basing on the the theory of deflection basin measurement and modulus inversion of asphalt pavement structure layer,it mainly was discussed the differences of equivalent elastic modulus of different asphalt pavement structures including cushion layer,cement stabilized macadam layer and transition layer determined by theoretical calculation method and inversion method.It could be concluded that the differences of equivalent springback modulus between two methods were mainly due to the determination of equivalent springback modulus on top of cement stabilized macadam.Therefore,the modified formula of equivalent springback modulus was put forward.5)Basing on the argumentation to the reliability of the performance test system of asphalt pavement,the evaluation parameters used include the strain of asphalt layer bottom,the vertical compressive stress on the top of the sub-grade or bottom of the transition layer and the vertical displacement of the transition layer.The dynamic response properties of three kinds of asphalt pavement structures were studied basing on driving load,and the effects of driving speed vehicle type and axle load were analyzed on the dynamic response properties of pavement structure.It could be concluded that the sensitivity of semi-rigid base asphalt pavement to driving state was higher than that of rigid and flexible compound base asphalt pavement.At the same time,basing on the pavement structure performance test system and temperature,the humidity test system,the variation internal humidity properties of the pavement structure were revealed during rainfall,the response properties of rigid and flexible compound base asphalt pavement were discussed under the coupling of humidity and dynamic load,and the sensitivity of pore water pressure in transition layer to driving speed and axle load was analyzed.Futhermore,the influence of seasonal variation on the response properties of different pavement structures were discussed in field tests.It can be concluded that the graded crushed stone has good drainage property,as well as the rigid and flexible compound base asphalt pavement has better suitability in the hilly area of East Sichuan. |
PDF Full Text Request