Research On Pavement Splicing Technology For Reconstruction And Expansion Project Of Jiqing Expressway

With the rapid development of the national economy,the traffic volume of expressways has increased sharply,resulting in the original two-way four-lane expressway not meeting the demand for rapidly growing traffic volume,and improving the traffic capacity through the way of highway reconstruction and expansion.Based on the reconstruction and expansion project of Jiqing Expressway,the paper investigates the old road disease investigation,traffic composition and axle load spectrum,longitudinal crack cracking mechanism,subgrade settlement characteristics and treatment measures,pavement splicing and the six sections of the Jiqing Expressway.Research on new and old pavement splicing simulation and other aspects,to provide reference for solving the problem of highway reconstruction and expansion.The main research contents are:(1)Investigate the use condition of existing asphalt pavement,analyze the characteristics of road pavement structure and the bearing capacity(deflection)of the old road,and invert the structural parameters of the old road.The main diseases of the old road are cracks and ruts,and the pavement structure layer modulus The difference between the different wheel tracks is obvious,and the modulus of the pavement structure of the heavy-duty driveway is low.(2)Analysis of traffic volume and axle load spectrum,based on the 2017 version of the new asphalt pavement design specification vehicle and axle type classification method,the typical section traffic volume,vehicle type classification,axle number coefficient,traffic volume distribution coefficient of Jiqing Expressway Traffic parameters such as axle load spectrum were statistically summarized,and the traffic composition and axle load spectrum characteristics were summarized.(3)Study the mechanism of top-down cracking of spliced asphalt pavement by theoretical calculation.According to the common longitudinal crack problem of expressway,according to the grounding shape of the wheel load and the grounding pressure of the tread,the three-dimensional finite element model of the wheel load and the widened spliced asphalt pavement structure is established,and the maximum shear of the spliced pavement structure under different load conditions is calculated.Stress and tensile stress and their location.The research indicates that the key source of asphalt pavement structure and material damage in the highway reconstruction and expansion project is that under the overload condition,the crack that expands the top layer of the spliced asphalt surface layer from the top to the bottom is caused by the road surface shear stress.(4)For the problem of differential settlement between new and old roadbeds,by analyzing the settlement mechanism of subgrade,different treatment schemes are adopted for silty clay,soft soil and Qiaotou sections.Among them,silty clay introduces four kinds of splicing methods;the soft soil section describes the replacement method and composite foundation treatment according to the soft foundation depth;the bridge head section uses the method of excavating vertical and horizontal steps and backfilling the permeable material.Subgrade splicing adopts different splicing treatment measures according to different filling and soil quality.(5)Combined with the physical engineering construction,the technology of existing asphalt pavement disease treatment,the new and old asphalt pavement splicing technology and the construction process of strengthening the connection between old and new interfaces were studied.In order to strengthen the interface between the new and old interfaces of the semi-rigid base layer,the interface treatment agent was selected by the pull test,and the optimum coating thickness and the amount of the coating agent were determined by the split test and the freeze-thaw split test.The pavement stitching and interface were summarized.Construction process.