Research On The Graded Gravel For Flexible Base Of Asphalt Pavement Structure In Tibet

The damage of road surface are mainly in the form of freezing and reflected cracks in semi-rigid asphalt pavemen for high elevation, cold climate and the relatively less traffic in Tibet. Compared with semi-rigid asphalt pavement , graded gravel asphalt pavement has better properties of anti-freeze and anti-reflective cracking. Researching on the graded gravel for flexible base of asphalt pavement is to improve the durability and to reduce costs of conservation and maintenance in Tibet. In addition, it greatly reduces project cost and promotes the development of transportation in Tibet.Through theoretical analysis combined with laboratory tests,this paper has studies the nonlinear property of graded gravel and the fatigue life of asphalt concrete in asphalt pavement; through the indoor test and detection ,the graded gravel for base of Asphalt Pavement is evaluated as follows:Test through the pilot study and the CBR's largest particle size than the largest diameter of 37.5 mm to 31.5 mm graded gravel mixture maximum dry density and CBR value should be large; through the water stability test study graded gravel mixed material has good water stability, 0.075mm content is part of the impact of graded gravel aggregate mixture of water the key to stability; through the resilient modulus study graded the largest size of gravel mixed with the resilient material modulus relationship between the different degree of compaction and the relationship between resilient modulus, water content and the relationship between resilient modulus, freezing and thawing of mixed gravel aggregate gradation modulus of resilience through the study of this class 37.5 ~ 31.5mm thick the presence of gravel-grade material mixed with gravel to increase the overall strength of a role to play, mixed gravel aggregate gradation in the degree of compaction 94% ~ 98% change in resistance to deformation when the material's ability to change little, with the gradation gravel mixed water evaporation capacity is expected be higher graded gravel mixture has good frost resistance, 0.075mm content is part of the impact of graded gravel material antifreeze mixture of the key;Combination of resilient modulus test results, through the theoretical analysis has established mixed gravel aggregate gradation before and after freezing and thawing of the non-linear bearing capacity model, graded gravel mixture before freezing and thawing of the nonlinear material model for bearing capacity of E = (296.5432 - 488.785σ3)σ1+ 254.4512, graded gravel mixture after freezing and thawing of the nonlinear material model for bearing capacity of E = (279.9624-465.345σ3)σ1+ 238.235; through graded gravel to asphalt pavement test indoor test tank and testing the selected studies the structure of the grass roots and the asphalt concrete is the main load-bearing layer, in order to reduce the road track, one aspect of the measures can be taken to improve the grass-roots level with gravel and asphalt concrete load-bearing capacity, and the other measures is to increase the thickness of asphalt surface; in Indoor split fatigue test based on the asphalt concrete strain fatigue equation, finite element method combined with the asphalt concrete layer to be at the end of the results of tensile strain on the test structure of asphalt concrete road surface for the fatigue life analysis, the findings of the trial road structure after freezing and thawing of the fatigue life of asphalt pavement is the only non-freezing and thawing of asphalt pavement for 56% of fatigue life, but regardless of whether the freeze-thaw damage is the two situations can meet the requirements of the fatigue life. Through graded gravel road test asphalt pavement and the paved road performance during the testing, grading gravel that flexible asphalt pavement cracks and breakage rates are far less than the semi-rigid asphalt pavement, grading Flexible Asphalt Pavement gravel has a good road performance.The results of research has based for non-linear characteristics of graded gravel materials and fatigue life of asphalt concrete pavement, and offers an important reference for graded gravelof asphalt Pavement in promotion and application.