Experimental Study On Mechanical Properties And Constitutive Model Of Artificial Frozen Remolded Peaty Soil

In order to better apply the artificial freezing method to the actual construction of the project,it is very necessary to study the mechanical properties of frozen peat soil.Taking peaty soil in a certain area of Yunnan,China as the research object,the physical and mechanical properties of peaty soil under freezing conditions were studied through a combination of laboratory mechanical tests and theoretical analysis.Firstly,uniaxial compressive strength test and uniaxial compressive creep test under different moisture content and freezing temperature were carried out,and corresponding stress-strain and creep test curves were obtained.According to the stress-strain test curve,the influence of different moisture content and freezing temperature on the peak compressive strength and elastic modulus is analyzed,and the corresponding functional relationship is established.At the same time,the stress-strain compressive strength constitutive model is introduced,considering the influence of moisture content and freezing temperature on the model parameters,the stress-strain compressive strength constitutive model considering the influence of moisture content and freezing temperature is established,and the calculated values of the model are compared.Compared with the experimental values,it is found that the model can better describe the relationship between stress and strain of frozen peaty soil.Secondly,according to the creep test curve,the influence of moisture content,freezing temperature and loading stress on creep deformation and creep deformation rate is analyzed.The creep deformation law is described by comparing the empirical model and the component model,and the Singh-Mitchell(S-M)empirical creep model and the Mesri empirical creep model are introduced.By taking the logarithm of the left and right sides of the model equation at the same time,the simultaneous cube calculate the model parameters.At the same time,the influence of different moisture content and temperature on the parameters of the model is analyzed,and the S-M creep model and Mesri creep model considering the influence of moisture content and temperature are established.Comparing the calculated values of the two models with the experimental values,the results show that the calculated curves of the two models can better describe the attenuation stage and the stable stage of the creep of frozen peat soil.However,the S-M creep model and Mesri creep model,which consider the influence of moisture content and temperature,are not ideal in describing the acceleration stage of creep.In order to be able to better describe the acceleration stage of the creep of frozen peaty soil,the fractional derivative function is introduced into the S-M empirical creep model,the damage variable factor is introduced into the Mesri creep model,and the influence of temperature on the model parameters is considered.This establishes a fractional derivative S-M creep model considering the temperature effect and a Mesri creep damage model considering the temperature effect.Taking the results of the uniaxial compression creep test with a water content of 20%and 40%as an example,the simulated annealing algorithm and the genetic algorithm are used to optimize the identification of the two model parameters.The results show that the two improved empirical creep models can better describe the entire creep deformation stage of frozen peat soil and predict the creep deformation trend,and the agreement is high.The classic Burgers creep model has a good description effect on attenuating creep,but the effect is not ideal in describing the acceleration stage of creep.Based on this,a viscoplastic model is proposed and introduced into the Burgers creep model.To establish a nonlinear viscoelastic-plastic creep model.Taking the results of the uniaxial compression creep test with a moisture content of 60%as an example,the simulated annealing algorithm is used to optimize the identification of the model parameters,and the calculated value of the model is compared with the test value.It is found that the nonlinear viscoelastic-plastic creep model can better reflect the freezing The creep deformation law of peaty soil.By adopting an improved empirical creep model and an improved element creep model to calculate the creep deformation value of frozen peaty soil,it makes up for the defect that the traditional model cannot calculate the deformation value during the accelerated creep stage,and is designed for better freezing,the wall provides a new way of thinking.Figure [39] Table [21] Reference [82]...