Study On The Structure And Material Design And Application Of The Subsea Tunnel Pavement In The Frozen Sea Area

The frozen sea area located in the northern coastal area of China has the characteristics of long frozen period,low temperature and complicated geological conditions.In addition to resisting the corrosion of sea water,the construction of the subsea tunnel in this area will overcome the influence of special weather,subgrade supporting condition and traffic characteristics on the construction of the project.The structure and material design method of ordinary highway tunnel or urban road can not meet the performance requirements under special use condition.But the research on subsea tunnel pavement in frozen sea area is almost blank and the design method of structure and material composition has not yet been formed under the special environment and technical requirements.According to the environmental characteristics and mechanical properties,durability,fire-retardant and environmental protection requirements of subsea tunnels in frozen sea area,the paper studies the pavement structures behavior and material design by theoretical analysis and application practice.Based on the mechanics analysis of structure,mechanical properties,fatigue performance and pavement performance of material,the design method of pavement structure and material for subsea tunnels is proposed,which provides the theoretical basis for pavement structure and material design of subsea tunnels in frozen sea area and makes up for the deficiency of the existing design method in the special environment and traffic characteristics of frozen sea area.Based on the characteristics of long slope,small temperature gradient,large traffic volume and light axle load of subsea tunnel pavement in frozen sea area,this paper puts forward the structural design idea and confirms the structural design parameters,failure mode and the most unfavorable load position.By using the finite element method,the dynamic response of pavement structures with different influencing factors is analyzed by using the dynamic modulus.The sensitivity of each factor to the structural stress response is discussed.A multi-index control system is designed for the subsea tunnel pavement thickness design.Based on the characteristics and performance requirements of the interfacial layer between the pavements in the frozen sea area,the key indexes of the performance evaluation of the waterproofing adhesive layer of the subsea tunnel in the frozen sea area are proposed.Comprehensive mechanics analysis and waterproofing layer performance test results,the paper recommends the thickness of the pavement structure and the implementation of waterproofing and bonding of the pavement layer in the frozen sea area.Based on the temperature and load conditions of subsea tunnel in frozen seas,the properties of the warm-mix and fire-retardant asphalt mixture are analyzed.The rheological testing technology is used to analyze the high temperature performance,low temperature performance and fatigue performance of warm-mixed asphalt with different types and contents.In this paper,the viscoelasticity index of warm-mixed asphalt material is studied with the type and content of warm mixed agent.The loss factor,50% attenuation position and DER are taken as the evaluation indexes of the asphalt fatigue performance.Based on the thermodynamics and viscoelastic structure,the asphalt time curve and cumulative dissipative energy fatigue curve were established.The influence of the warm-mixed agent on the asphalt fatigue characteristics is obtained.Based on the rheological technique and fatigue characteristics,the optimized content of warm-mixed agent is proposed.The suitable content range of Sasobit is 1.5~3%,Leadcap is 1~2% and ZQ is 7~8%.The limit oxygen index method combined with asphalt flash point and ignition point as a comprehensive index to evaluate the fire-retardant performance and construction safety to meet the fire-retardant and smoke-suppression requirements of frozen sea tunnel materials.The type and content of fire-retardants agent for subsea tunnel pavement in frozen sea area are determined.The design of warm-mixed and fire-retardant asphalt mixture composition for subsea tunnel pavement in frozen sea area is studied.The design idea of composition and the method of determining compaction temperature are proposed.The dynamic modulus and phase angle of different asphalt mixtures are tested by the simple performance test and the four point bending beam fatigue test.The relationship between stiffness modulus and load times of different asphalt mixtures is established.The influence of different warm-mixed agents on the fatigue life of asphalt mixture is explored,which will provide the theoretical basis for the design of subsea tunnel pavement materials.Based on the Jiaozhou Bay subsea tunnel project,the adaptability of the subsea tunnel pavement structure and material design method in the frozen sea area is verified.The paper analyzes the construction technology and social,environmental and economic benefits of the asphalt mixture.The results show that the toxic and harmful gases can be greatly reduced during construction and the effect of energy saving and emission reduction is obvious.The results of this paper provide theoretical support for the design and application of subsea tunnel pavement structures and materials in the frozen sea area,and also have reference significance and popularization value for tunnel pavement design in other special environments.