An Internal-variable Creep Model Of Frozen Sand In Consideration Of Temperature And Moisture Content

The creep failure of frozen soil is often caused by its weight or other loads in the building structure or road engineering in frozen soil area,which makes the existing engineering have great hidden danger of safety.The study of frozen soil characteristics under various factors has become particularly important The traditional creep model of frozen soil is usually closely related to the creep time.When the external load environment changes,the initial state of soil changes accordingly,and the model is no longer applicable.The research object is sandy soil of a subgrade in Yulin,Shaanxi Province.Through the indoor test of artificial frozen soil and the establishment and verification of creep constitutive model,the strength characteristics of frozen sand under the influence of temperature and moisture content and the creep law under different loading levels are explored.This paper analyzes the creep characteristics of frozen sand from the perspective of internal variables,selects the irrecoverable strain as the internal variable of frozen sand,and based on the internal variable creep model of soil,considers the influence of temperature effect,moisture content and other factors respectively,establishes a comprehensive creep model with a wider scope of application.The model parameters can be obtained by simple calculation,and the physical meaning is more obvious.When exploring the creep damage model of frozen soil,the damage is defined according to Young’s modulus change in energy damage,and the internal variable creep damage model of frozen sand is established The parameters of the model are optimized and compared by particle swarm optimization algorithm.Finally,the reliability of the model is verified.In order to ensure the reliability of the test,a large number of laboratory tests of artificial frozen soil were carried out for remolded silty fine sand Four temperature levels(-5℃,-10℃,-15℃,-20℃)and six moisture contents(8%,10%,12%,14%,16%)were tested to obtain the average uniaxial compressive strength.The influence of temperature and moisture content on frozen soil strength was analyzed,and the theoretical formula of frozen sand strength related to temperature and moisture content was established Uniaxial creep tests of 0.1,0.2 and 0.3 loading levels were carried out on the specimens under the same conditions,and the creep curves under different factors were obtained In this paper,the internal variable theory is introduced into the creep of frozen sand,and the effects of temperature and moisture content on the creep of frozen soil are considered respectively.It is found that the creep models of the two grades can simulate the creep of frozen sand better by comparing the experimental values and fitting values of the models.Because the frozen sand has been seriously damaged during high-level loading,it is necessary to introduce damage variables into the model to establish a creep damage model of frozen sand,which can describe the accelerated creep stage.Particle swarm optimization algorithm is used to identify the model parameters,and the parameters obtained by the intelligent algorithm are compared with the calculated values to verify that the derivation process of the model is reasonable.The results show that the internal variable theory can also be used to describe the creep process of frozen sand.Figure[39]Table[6]Reference[82].