| The pavement structure in the tunnel has its special working environment.The pavement in the tunnel is in a relatively closed environment,which is directly affected by factors such as sunlight and rain,and the temperature field in the tunnel and the strength of the underlayer are also different from those of ordinary road sections.Channelized traffic is strict,acceleration and deceleration are frequent,and the performance of tunnel pavement and the mechanical response under load also have their own characteristics.Based on the investigation of tunnel pavement structure composition,disease type,environmental characteristics,etc.,this paper carried out numerical simulation on the stress-strain response characteristics of three types of pavement structures such as tunnel composite pavement,flexible pavement,semi-rigid base asphalt pavement Research;adopt the all-environmental pavement accelerated loading test system to conduct 1 million times of accelerated loading tests on the composite pavement and flexible pavement in the tunnel paved on the site,and based on the strain response and temperature field collected by the accelerated loading test The strain response of pavement and flexible pavement structures was analyzed.(1)The investigation results of tunnel pavement indicate that the current structure of tunnel pavement in China is dominated by composite asphalt pavement;the diseases of tunnel pavement are dominated by transverse cracks of asphalt pavement;the structural analysis of tunnel pavement in the past is mainly based on theoretical analysis.There are few related experimental studies.Although the full-scale pavement can simulate the site situation well,there are few studies on the design of the pavement structure in the tunnel.(2)The simulation results of the tunnel composite pavement indicate that the thickness of the asphalt layer is a key factor affecting the fatigue expansion life of the tunnel composite asphalt pavement.The thicker the asphalt,the greater the fatigue expansion life.The thickness of the concrete layer,the reinforcement mesh in the cement concrete base,the thickness of the base and the modulus of the asphalt surface layer,and the continuous reinforced concrete have little effect on the fatigue extension life of the tunnel composite asphalt pavement.Combined with the investigation results and simulation analysis results,considering the technical and economic aspects,it is recommended to use plain concrete for the composite pavement in the tunnel and SMA for the asphalt surface layer.(3)The simulation results of the semi-rigid base asphalt pavement in the tunnel show that the fatigue cracking life of the semi-rigid base asphalt pavement surface in the tunnel is far greater than the design life.For the asphalt surface layer of the semi-rigid base asphalt pavement in the tunnel,fatigue life is not a key indicator.The permanent deformation of the semi-rigid base asphalt pavement in the tunnel has a great relationship with the structural composition,and the improper structural combination,the permanent deformation cannot meet the design requirements.(4)The simulation results of the flexible base in the tunnel show that the thickness of the asphalt surface layer has the greatest influence on the permanent deformation of the top surface of the asphalt surface layer compared to the ATB modulus,ATB thickness and asphalt surface layer modulus.(5)Temperature field in the tunnel pavement structure: the summer pavement structure temperature in the tunnel is 26～32℃,it can be seen that the temperature of the pavement structure in the tunnel is much lower than the temperature in the pavement structure outside the tunnel;the temperature range in the pavement structure layer is(6)When the thickness of the asphalt surface layer of the compound pavement of the tunnel is thickened and the reinforced mesh is provided in the concrete layer,there is no significant difference in the cumulative strain,peak value,trough value and amplitude of the bottom strain of the upper layer of the asphalt.In the compound pavement in the tunnel,the total thickness of the asphalt surface layer has no significant effect on the bottom strain of the asphalt upper layer.(7)When there is no reinforced mesh in the concrete layer of the compound pavement of the tunnel,there is a significant strain position in the concrete at the non-slit position,that is,at a depth of 20 cm in the concrete,there is a transition zone between tensile and compressive strain,The strain in this area is close to zero.The reason for this phenomenon may be that within a period of time after the concrete is poured,due to the effects of temperature shrinkage and dry shrinkage,there is tensile stress caused by temperature shrinkage and dry shrinkage inside the concrete,and the bottom of the concrete is due to the The restraint action produces compressive str... |
