Simulation Study On Impact Resistance And Decay Law Of Airport Rigid Pavement

The airport pavement is the infrastructure to build the air transport system.With the increase of flight frequency and the use of heavy aircraft,the airport pavement loses surface function and structural performance prematurely during the service period.Aircraft landing impact is one of the important reasons for the deterioration of pavement structure performance.The damage law of pavement under aircraft impact has important reference value for pavement structure design.However,there is still a lack of research on the internal damage evolution law of pavement structure under aircraft landing impact.Therefore,this thesis systematically studies the impact resistance and decay law of airport rigid pavement structure.The research contents and main conclusions are as follows :(1)Based on the concrete damage constitutive theory,according to the mechanical analysis characteristics of the airport rigid pavement structure and the material properties of the structural layer,the concrete plastic damage model is selected as the material constitutive of the numerical calculation by comparing the existing concrete damage constitutive model.The mechanical behavior and control rules of the concrete plastic damage model are clarified.According to the uniaxial tensile stressstrain curve provided by the current cement concrete structure specification,the plastic damage parameters of the cement concrete surface material are obtained by formula deduction,which provides material parameters for the model construction and provides a theoretical tool for the damage evolution analysis of the pavement structure.(2)The aircraft load simulation is carried out,and the wheel load parameters are calculated and the landing impact load waveform is fitted according to the aircraft load parameters and the landing impact load characteristics.A three-dimensional numerical model of airport rigid pavement structure is constructed by using the general finite element software ABAQUS.Based on the numerical model,the effects of different aircraft load forms(aircraft landing gear configuration,load position)and pavement structure parameters(surface layer thickness,surface layer modulus,base layer thickness,base layer modulus,soil base modulus)on the impact resistance of airport rigid pavement are analyzed.The analysis results show that the mechanical response of pavement structure under complex aircraft landing gear shows obvious multi-wheel superposition effect.Under the same tire pressure,the vertical displacement under the action of three-axis double wheels is 1.83 times that of single-axis double wheels.The most unfavorable load position of the rigid pavement structure of the airport under the impact load of aircraft landing is the middle of the longitudinal seam edge;surface thickness is the key structural parameter to improve the impact resistance of pavement structure.(3)The finite element software combined with FORTRAN language is used to develop the subroutine,and the temperature field model of airport rigid pavement structure is constructed.The overall temperature change of pavement structure under the action of high temperature daily cycle in summer is calculated.Based on the calculation results of temperature field,the temperature-impact load response analysis is carried out to explore the influence of ambient temperature on the impact resistance of pavement structure.The results show that the influence range of ambient temperature is mainly concentrated on the surface structure.The temperature field of the structure changes periodically with the ambient temperature.Under the action of temperature-impact load,the ambient temperature is positively correlated with the deflection at the top of the pavement and the tensile stress at the bottom of the cement concrete slab.Under the daily temperature cycle,the range of the top deflection can reach 0.642 mm,and the range of the bottom stress can reach 1.61 MPa.The impact resistance of the pavement structure decreases with the increase of temperature.(4)Based on the three-dimensional numerical model of airport rigid pavement,the dynamic response of rigid pavement under single impact load and periodic impact load is analyzed.Taking the bottom stress,vertical stress and displacement as the key to characterize the impact resistance performance index of pavement,the variation law of three indexes along the transverse layout and section depth of pavement under single impact load is observed.Taking compression damage,tensile damage,plastic deformation and stiffness degradation rate as the key parameters to characterize the damage degradation index of pavement structure,the damage evolution process and time history variation law of each index of pavement structure under different impact cycle periods are observed.The research results reveal the attenuation law of impact resistance of airport rigid pavement structure from two aspects : overall dynamic response of structure and overall damage evolution of structure.