Study On The Initiation And Propagation Mechanism Of Reflective Crack In Asphalt Pavement And Induced Crack Technology

Reflective cracking which seriously affect pavement fatigue life and driving safety is widely existed in our country's highway and become into a hard problem to deal with. Traffic load and temperature load are two main factors accounting for its formation and propagation. In this paper, linear fracture mechanics is employed to give a full analysis to the mechanism of reflective crack's propagation and the reasonable spacing of the induced crack technology is studied as well.Firstly, after depicting the singularity of stress field at the top of crack, the finite element method to calculate stress intensity factor of plain fracture problems is founded.Secondly, the structural response of pavement suffering reflective cracking is deeply analyzed in terms of traffic load and thermal load. As for traffic load, two situation were analyzed, symmetrical load and asymmetric load, in each of them, crack top's tension stress, shear stress and stress intensity factor were calculated, also the effect of structural parameters were analyzed. Pavement's temperature distribution field when suffering sudden temperature dropping was numerical simulated. Crack top's tension stress and stress intensity factor caused by thermal stress were computed, structural parameters' sensitivity analysis were made as well. Then, reflective crack's propagation model under traffic load coupled with temperature load was analyzed. At last, reflective crack's propagation speed of different pavement structural combination was analyzed too. The analyzing result indicated that reflective crack's propagation model is decided by the stress at top of the crack, which often is a compound propagation model. By parameter analysis, reflective crack's propagation potential and speed are also cleared.Thirdly, taking into account thermal stress, friction between surface and base and friction between base and soil, a mechanical model representing the pavement including induced crack is founded. The maximal tension stresses in surface and base between induced crack have been obtained by parametric analysis. Then, taking the maximal tension stress in surface and base and the stress intensity factor at the top of the induced crack as restraining indexes, method to determine the reasonable induced spacing has been determined.