Research On Mechanical Characteristics And Design Method Of Graded Crushed Stone Material

Graded crushed stone flexible base can efficiently mitigate the asphalt pavementcracking by the good ability of stress dispersion, and it is much more economical. Althoughwidely used as the base of pavement, graded crushed stone is seldom used in base course ofhigh-grade highway, it is mainly because the testing method of graded crushed stone incurrent criterion cannot go with the present producing practice; Mechanics characteristics ofthe indoor experimental research method, it is difficult to essentially reveal the gradingmacadam material nonlinear mechanics properties and failure mechanism by mesoscopicmechanism; Gradation scope is too broad for quality control, lack of the specific designmethod of grading macadam material; Design modulus is based on the test method of staticmodulus, that is not match the pavement actual stress state; Material design indexes are moreor less incomplete and insufficient, so the essence of graded crushed stone mechanicalcharacteristic can not be truly known, and the recommended designing method can notefficiently optimize the mix designing and guide the practical construction. Based on above,this paper makes study on the mechanical characteristic and design method of graded crushedstone material, and it makes more practical sense.First, by means of experimental studies on the inter-affection of VVTM dynamicresponse, compaction effect and site-rolling effect, VVTM vibrating parameters andtime-period are optimized, and graded crushed stone vibrating test method is proposed, and itsreliability is verified through the actual rolling effect; Research the material compositiondesign and mechanical properties of graded crushed stone by VTM, this paper discusses thenature of law on the structure and mechanical properties of graded crushed stone, and then therelationship between intensity index is summed up.Secondly, by operating granular flow simulation of laboratory experiment process andresult, and continuously debugging the micro-parameters, a high fidelity granular flow testingmethod (PSTM) for Mechanical properties of graded crushed stone is proposed. This methodsolved problems in constitutive study by continuous medium mechanics means, and make upfor the deficiency of the indoor test, and based on PSTM researches graded optimization andmesoscopic mechanism mechanical properties, then the VTM optimized gradation is vertified,finally the strong interlocked skeleton dense gradation is proposed.Based on VTM and PSTM, by the research on dynamic modulus of grading macadam,the rebound modulus prediction model is established, and combining the actual stress level ofgraded crushed stone base, the recommended value of design modulus of grading macadam is put forward; Based on the cumulative deformation test, carried out the research on permanentdeformation accumulation regularity and permanent deformation destruction standard, thenthe critical failure stress levels is determined, and combined with the simulation experimentresearch on the permanent deformation accumulative destruction, the permanent deformationaccumulative damage prediction model is established, and then graded crushed stone shearingstrength coefficient recommended value of different pavement structure type and traffic levelsis put forward, it provides the basis for establishment of shear stress index and forrmulate ofdesign standards.By investigating the mechanical response of graded crushed stone structure layer undertraffic load, aiming at preventing cumulative permanent deformation cumulative damageunder repeated load, on the base of the grading macadam mechanical response, relationshipbetween the strength index and shearing strength coefficient, proposed the design based onCBR index, RC as test indexes of grading macadam design standards, and combined with theresearch conclusion of optimization gradation and raw materials technical indicators, thedesign method of grading macadam material is put forward, and its performance is verifiedthrough real engineering application. Engineering application shows that grading macadammaterial designed by the method enhances the bearing capacity and deformation resistance ofgraded crushed stone base, which greatly solved the problem of the graded gravel shearfailure, and showed obvious economic and environmental benefits, it provide a basis for theapplication for the graded crushed stone.