Numerical Analysis Of Ulter-thin Asphalt Overlay Structure Of Old Cement Pavement With Active Passive Mode Anti Reflection Crack

Asphalt overlay is a common method to repair and improve the old cement concrete pavement.It can not only effectively improve the structural performance and use function of the original road,but also improve the driving comfort and safety of drivers.However,when the repaired pavement structure is used for a long time,under the repeated action of temperature and vehicle load on the joint position of the old cement pavement,the pavement structure will gradually generate cracks and eventually expand and penetrate the new overlay structure,making the pavement surface appear many types of cracks.In order to study how to effectively slow down the expansion of reflective cracks in the new overlay structure,referring to the existing research methods,to explore the mechanism of reflective cracks in the old cement pavement overlay structure,and lay the foundation for proposing the active and passive anti cracking system.ABAQUS finite element software is used to study the influence of related objects in active and passive systems on the propagation of reflection cracks.At last,the effect of active and passive prevention and control of reflection cracks is verified by the relevant test section engineering and follow-up investigation.In this paper,fracture mechanics is taken as the main theoretical basis to analyze the crack propagation mechanism.Based on the prevention and resistance of reflection cracks,a crack prevention system combining active and passive modes is proposed for the source of reflection cracks and the mitigation of reflection cracks.Based on fracture mechanics and thermodynamics,a three-dimensional finite element model is established with ABAQUS finite element analysis software,which takes grouting material at the bottom of slab,stress-absorbing layer and asphalt overlay as the main research objects,and explores the influence of the change of relevant parameters of each research object on the stress intensity factor at the crack tip under the action of temperature and vehicle load.Finally,according to the above analysis results,the active and passive anti crack system is applied to the maintenance and repair project of the cement concrete pavement of the Sanshui x495 west line in Foshan.During the construction process,the relevant technological process is determined and improved,and the post construction quality is inspected from multiple perspectives after the completion of the construction.On this basis,the test section is tracked,investigated and evaluated for a long time.The results show that: when the wheel load acts on the corner of the slab,the possibility of crack expansion is greater than that of the middle of the edge of the cement slab joint;when the local void and range void appear at the corner of the slab joint,after grouting treatment,it can effectively reduce the possibility of crack expansion and cracking under various load conditions,and the larger the void size,the more obvious the repair effect after grouting;The increase of modulus of grouting material can reduce the possibility of open crack propagation;in asphalt overlay structure,the selection of stress-absorbing layer with smaller modulus and asphalt overlay with larger modulus is more helpful to reduce the possibility of crack propagation;when the total overlay thickness is fixed,the thickness of stress-absorbing layer is smaller,and the combination of asphalt overlay with larger thickness is more helpful to reduce crack propagation It is proved that the active and passive anti cracking system has a good effect on protecting the old cement pavement,resisting the reflection cracks and improving the function of the pavement through the actual engineering cases and long-term road condition tracking.