Theoretical Study On Mechanical Properties And Stability Analysis Of Airport Runway Permafrost Foundation

In recent years,China's airport construction has developed rapidly,airport construction in permafrost environment is becoming a hot spot.The long-term deformation and strength control of permafrost foundation are the key factors related to the success or failure of the project.The study of the mechanics characteristics and stability analysis theory of runway permafrost foundation is the key to achieve the above goal.Based on the above background,the main research work and achievements are as follows:1.The aircraft static and dynamic load characteristics of airport runway permafrost foundation and equivalent method research.Based on the road roughness simulation,the dynamics and the vibration theory,the impact load caused by the road roughness on the road surface is calculated,and the finite element software is used to study the static and dynamic effects of the aircraft pavement Law.It is found that the dynamic characteristics of the permafrost foundation are mainly long-term low-cycle cyclic loads,laid the foundation to study its mechanical properties and stability.Based on the damage equivalent theory,the equivalent model of dynamic stress is proposed,and the combination of irregular dynamic stress wave pattern is equivalent to the standard wave type,and the dynamic stress of the combined traffic volume is equivalent.2.Permafrost deformation and stability analysis.Based on the three-axis experiment of permafrost,the dynamic triaxial test of permafrost is carried out,and the variation of mechanical parameters of frozen soil is analyzed systematically.The dynamic elastic modulus of permafrost with temperature,Confining pressure and other external factors;the accumulation of plastic deformation of frozen soil with temperature,confining pressure and other external factors of the law;and improve the data processing methods;frozen soil dynamic modulus of the factors significant test.3.Non-yield surface dynamic viscoelastic-plastic model based on uniform constitutive theory of viscoplastic damage.Based on the analysis of the deformation mechanism of frozen soil,it is pointed out that the dynamic elastic-plastic constitutive model of the existingpermafrost is insufficient,that is,the permafrost will accumulate under the long-term low cyclic loading,and there is no complete elastic deformation.Based on the unified constitutive theory of viscoplastic damage,the modified Cambridge model is improved,and establish the constitutive model of the non-yield surface dynamic viscoplasticity.The plastic strain of the frozen soil is calculated.The viscoelastic constitutive theory of the frozen soil is established by introducing the viscoelastic constitutive theory with attenuation constitutive model,the elastic strain is calculated.The calculation shows that the model can simulate the dynamic strain of permafrost in various mechanical forms.4.Based on the above results,this paper put forward the method of calculating long-term deformation and stability of airport permafrost.The dynamic behavior of the aircraft is analyzed.The dynamic stress of the frozen soil is calculated by the dynamic the equivalent model.The cumulative strain and creep of the frozen soil are calculated by dynamic elasto-plastic constitutive model and creep model.