| The quick repair technology of precast and assembled concrete pavement is a fast,environmentally friendly and economical repair technology that uses the precast cement concrete slabs to replace the damaged part of the original cement concrete pavement.Prefabrication and maintenance of cement concrete slabs and other processes are carried out at the backcourt.Only the removal of the old boards and the cutting of the grass roots,as well as the lifting and jointing of the new boards are carried out at construction site.It only takes 4 to 6 hours to open the traffic.This technology has the advantages of quick opening of transportation and lower cost of construction,with good durability,small impact on the environment,and strong adaptability to the construction site.The key of this technology includes precast slab structure design,precast slab hoisting scheme design,precast slab loading scheme design,grassroots leveling technology,precast slab leveling and joint processing technology,and the damage prevention measures of the precast slabs.At present,there are few researches on this technology in China,and a set of technical methods that can guide application is not yet formed.The paper mainly adopts the finite element analysis method,and systematically analyzes various types of precast and quick-fixed key technologies.A theoretical basis is provided for the application of the technology in practical projects.Firstly,the prefabricated slab structure design is analyzed,and the finite element software is used to establish the structure model of monolithic precast slab.Under the static load,the influence of the precast slab size on the mechanical response of the pavement structure is analyzed.Four schemes are proposed to repair the entire prefabricated panel,combined with the actual road panel block division conditions.Based on the four repair schemes,the sensitivity parameters of prestressed pavement structure mechanics is analyzed.The temperature stress of precast slabs structure and the design of precast slab lifting scheme are analyzed.The results show that the load stress of the large size plate is small,but both the thermal stress and the plate bottom tensile stress are high,while the small size slab has a relatively higher load stress,but the temperature stress and the plate bottom tensile stress when lifting are low.The tensile stress of the precast slab bottom is inversely proportional to the base modulus and the soil-based modulus.Secondly,the design of the load transfer plan of precast slabs is analyzed.Based on four repair schemes,finite element software is used to establish load transfer models of the structures of precast slabs.Firstly,the mechanical responses of the structures under dynamic and static loads are analyzed.Based on the load transfer capacity,the reliability of the static load model of the structure is determined.Then the influence of the arrangement of the transmission rod and the parameters of the transmission rod on the load transfer capacity is analyzed.The application of the new dowel steel type of GFRP in the precast slab structure is further analyzed.The results show that the load transfer capacity is inversely proportional to the spacing of the dowel steel,and is proportional to the modulus of the dowel steel.The existing design of the transmission dowel steel in the highway concrete pavement design can also be applied to the design of the precast slab structure.When the GFRP dowel steel is applied to the pavement load transfer device,it can reach the load-bearing capacity of the pavement joint when the traditional dowel steel is laid in accordance with the minimum requirements of the standard of 30 cm only when 36mm diameter is laid at a spacing of 10 cm.Thirdly,the leveling layer is analyzed.The gap between the basic layer and the precast slabs is filled with the leveling material.The requirements is proposed for the performance of the leveling material through finite element modeling analysis,and the reliability of the leveled material is tested through experiments.The verification results show that the leveling layer material prepared by the dissertation can meet the road performance requirements under the action of overweight loads.Finally,the prevention and control of cracks of the precast pavement are studied,and precast pavement structures with cracks is established.Without the prevention and control measures,the variation law of the crack tip stress and stress intensity factors under the axle load is analyzed.With the control measures,the variation law of the crack tip stress and stress intensity factors under the static load is analyzed.Combined with the results of the crack propagation under heavy load,the results show that the stress at the bottom of the precast slab and the stress intensity factor at the crack tip are inversely proportional to the FRP modulus and the interfacial stiffness,and that the layout of FRP can not only delay or prevent crack propagation,but also improve the bearing capacity of pavement structure. |
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