Research On Typical Structure Of Asphalt Pavement In Highway Tunnel

In recent years,the demand for the construction of long highway tunnels in my country has been increasing,and the research on the design scheme of tunnel pavement has been slow.At present,the research results of researchers from various countries on tunnels mainly focus on structural design,tunnel ventilation,tunn el lighting,and construction technical standards.Compared with ordinary asphalt pavement and cement concrete pavement,the service environment of tunnel pavement is quite different,so it is necessary to conduct in-depth research on the design method of tunnel pavement structure.Based on the technical analysis of the previous structural combination of tunnel highways,this paper proposes three typical structural forms of asphalt pavement for highway tunnels based on theories and specifications combined w ith years of application experience in tunnel pavement.Using the numerical analysis method of ABAQUS finite element simulation,the static load response laws of three tunnel pavements under different horizontal loads,vertical loads,interlayer bonding st ates and surrounding rock modulus were analyzed and compared under saturated and anhydrous conditions.Stress condition of the road surface.Combined with "Code for Design of Highway Asphalt Pavement" JTG D50-2017,design control indicators for three types of tunnel pavement are proposed respectively.The main research conclusions are as follows:(1)The temperature conditions and roadbed conditions in the tunnel are favorable to the service condition of the road surface,while the humidity conditions and traffic conditions in the tunnel are unfavorable for the service condition of the road surface.From the aspects of durability,skid resistance,wear resistance and maintenance difficulty,tunnel asphalt concrete pavement has great advantages compared with tunnel cement concrete pavement.(2)The key control indicators of the asphalt pavement of the rigid base of the tunnel are the permanent deformation of the asphalt mixture layer and the internal tensile strain of the asphalt layer;the key control indicat ors of the asphalt pavement of the semi-rigid base of the tunnel are the permanent deformation of the asphalt mixture layer and the internal tension of the asphalt layer.Strain;the key control indicators of the asphalt pavement on the flexible base of th e tunnel are the bottom tensile strain of the asphalt mixture layer,the permanent deformation of the asphalt mixture layer and the internal shear stress of the asphalt layer.(3)When the surrounding rock grade is above grade IV,the continuous increase of the surrounding rock modulus has little effect on the overall structure of the pavement;the horizontal load has a great influence on the tensile stress of the road surface and the shear stress of the asphalt layer,especially the asphalt of the flexible base of the tunnel.On the road surface,in the case of emergency braking,the asphalt layer is prone to shear damage.(4)Under water-saturated conditions,the stress and strain of the asphalt pavements in the three tunnels increased under the load,and the pavement structure was more likely to be damaged.The order of sensitivity of three tunnel asphalt pavements to water environment is: rigid base > semi-rigid base > flexible base.Under the water-saturated state,the stress and strain increase of the a sphalt pavement of the flexible base of the tunnel is small,and it has certain advantages in service in the tunnel with rich groundwater.