Study On Overlay Structure Of Highway Overhaul Project In Hunan Province

After many years of traffic loads on some early-built highways,the general repair and intermediate repair can not meet the requirements of vehicle safety and comfort with the gradual improvement of China's highway infrastructure construction.It is urgent to overhaul and improve the overall structural performance of the road.The existing research on the overhaul structure of highway overhaul project is not systematic,and it is of great significance to carry out research on the pavement structure of Hunan Expressway overhaul project based on physical engineering.Based on the overhaul project of Tanshao Expressway in Hunan Province,this paper studies the overlay structure of the overhaul project.Through collecting relevant design and construction data,the data of deflection basin of three overlay structures are collected by drop-weight deflectometer.By collecting the temperature data,the finite element model of the temperature field was established,and the temperature of the asphalt layer at different depths was simulated by finite element method,the average temperature of the asphalt layer was calculated.By setting the presence or absence of the rigid underlying layer,the SIDMOD and EVERCALC programs are used to inversely calculate the modulus of the overlay structure,the dynamic modulus of the three types of overlay structures are obtained,and the factors affecting the accuracy of the results are analyzed from different angles.At the same time,ABAQUS finite element method is used to establish three-layer structure model,and the inversion results of SIDMOD program are used as initial values to fit the deflection basin,which verifies the reliability of the inversion results of SIDMOD program.By fitting the measured deflection basin with BISAR program,the modulus combinations of theoretical deflection basin and corresponding structural layers of three overlay structures with higher fitting degree are obtained.Taking the modulus combinations as a benchmark,and taking asphalt direct overlay structure as an example,the variation rule of deflection basin with structural parameters of pavement structure under FWD is calculated and analyzed.The results can provide reference for overhaul engineering and new engineering thickness design and structural material selection.For the deflection value of Beckman beam measured by the old road,the stiffness of the paved overlay material is checked by means of CMSR program,and the minimum stiffness required by the overlay material is calculated.On the basis of referring to the range of current codes,the modulus combination of the structural layers obtained by fitting is reduced to a certain extent,and the corresponding checks are carried out for the three overlay structures.The results show that the three overlay structures meet the requirements of the design codes.The key technical quality control points of three kinds of overlay structure entity engineering are elaborated,and 3D ground penetrating radar detection is carried out for overlay structure entity engineering.The disease type analysis and physical engineering are carried out by taking the direct overlay structure of the old asphalt pavement as an example.The calculation results of radar thickness show that it is feasible to use the radar detection value as the modulus back-calculation thickness parameter value when performing the back-calculation of each test point.The research results can provide theoretical basis and reference for improving the design and construction technology of the overhaul project of the highway overhaul project in Hunan Province.It has practical significance for prolonging the service life of the pavement,reducing waste of resources and reducing maintenance and repair costs.