Research On Utilization Technology Of Hardened Layer Of Rock-filled Subgrade Beam Field And Optimization Of Pavement Overlay Structure

The terrain of the mountain expressway construction project is complex and changeable.and the usual treatment method of removing the hardened layer of the subgrade beam yard of the main route will squander resources and contaminate the environment.At present,there is a lack of research on the utilization technology of the hardened layer of the beam field of the rock-filled subgrade.For building a "resource-saving and environment-friendly" highway,the research on the utilization of the hardened layer in the beam field of the rock-filled subgrade and the optimization design of the pavement structure for the hardened layer are carried out.The work has theoretical value and engineering guiding significance for improving the systematic study of beam field hardening layer utilization technology.A technological proposal for the use of the hardened layer of the beam yard of the rock-filled subgrade has been developed based on "Guanglian Expressway" project.When the elevation of the hardened layer is lower than the elevation of the top surface of the roadbed,the deflection is less than the deflection of the top surface of the rock-filled subgrade,indicating that after the gravel is filled on the hardened layer to the elevation of the top surface of the roadbed,the acceptance and pavement design can be carried out according to the rock-filled subgrade with rigid interlayer.When the elevation of the hardened layer reaches the roadbed elevation,the deflection is less than that of the top surface of the rockfill subgrade,indicating that it can be used directly.The top elevation of the hardened layer was re-measured,and carry out the modulus back-calculation of the hardened layer at different elevations.Combine Portable fallingweight deflectormeter(PFWD)and the Beckman beam(BB)method to test the resilient modulus of the hardened layer of the beam field.In the test,the dynamic deflection and dynamic resilient modulus results of different road sections under the two detection methods were fitted with the back-calculated static deflection and static resilient modulus,and it was discovered that the results of backcalculation of PFWD and BB were significantly correlated.The quick detection method of the equivalent resilient modulus of the top surface of the rock-filled subgrade with the beam field hardened layer is used to determine the PFWD to replace the BB method.The results of backcalculation can comprehensively evaluate the mechanical properties of the beam field hardened layer and provide design parameters for the optimization of the pavement overlay structure.According to the different elevations of the hardened layer,the optimal design of the pavement overlay structure is carried out,and the pavement overlay structure is checked and calculated according to the current specifications.The test findings all fulfill the requirements of specification,indicating that the optimal design of the pavement overlay structure scheme for the hardened layer containing the beam field is feasible.For further comparison the mechanical properties of each optimized design scheme,the ABAQUS software was used to carry out numerical simulation of pavement structure scheme,and the vertical displacement of the pavement,the vertical compressive stress of the asphalt surface layer,the tensile stress of the semi-rigid base layer,and the rutting of pavement structure scheme were calculated.The results show that the mechanical response of the original scheme is better when the elevation of the hardened layer is less than that of the roadbed;the mechanical response of the composite pavement structure is the best when the elevation of the hardened layer reaches the elevation of the roadbed.The research results can provide empirical reference and theoretical basis for the reuse of the hardened layer of the beam field and the optimization design of the pavement overlay structure in entity engineering,and have certain engineering guiding significance.