Study On Dynamic Characteristics And Creep Properties Of High Temperature Frozen Soil Under Traffic Load

High-temperature frozen soil has strong temperature sensitivity and unstable mechanical properties,which makes the types of freeze-thaw disasters more complicated,which severely restricts and affects the construction of cold-region projects,such as the construction of strategic channels for energy and transportation in China,Russia,and Mongolia.In recent years,with the national " The Belt and Road Initiatives " initiative and the 14 th Five-Year Plan,a large number of traffic engineering projects will be settled in cold areas,and research on high-temperature frozen soil will be carried out.On the one hand,it can enrich the research results of frozen soil mechanics,on the other hand.It will provide theoretical support for the treatment or protection of permafrost in engineering construction in cold regions.In this paper,the dynamic characteristics of high-temperature frozen soil are studied through low-temperature dynamic triaxial tests,and the effects of temperature,frequency and amplitude on the dynamic characteristics of high-temperature frozen soil are analyzed.Secondly,the dynamic stress-strain relationship of high-temperature frozen soil is studied.That is,the characteristics of the hysteresis curve and the dynamic creep characteristics of high-temperature frozen soil,the detailed conclusions are as follows:(1)The dynamic strain-vibration frequency curve of high-temperature frozen soil exhibits three types: stable,destructive,and transitional under the action of different dynamic load amplitudes.The characteristic of the stable curve is that the strain increases rapidly in the initial stage.After entering the stable stage,the strain growth rate is close to0,and the strain remains almost unchanged at this time;the destructive curve obtains a very high strain growth rate in the initial stage After that,the strain growth rate gradually attenuates with the vibration frequency until it reaches failure;the middle curve characteristic is between the former two,and the strain increases rapidly at the initial loading stage.As the vibration frequency increases,the strain increase rate gradually slows down.Eventually it reaches failure,but the strain growth rate is stronger than that of the stable type and weaker than that of the destructive type.(2)When the dynamic stress amplitude is 30 kPa,the dynamic elastic modulus of the high-temperature frozen soil first increases and then decreases with the development of the vibration frequency;when the dynamic stress amplitude is 40 kPa and 50 kPa,the dynamic elastic modulus of the high-temperature frozen soil increases with Zhenci’s development maintained a small growth.(3)The dynamic strength of high-temperature frozen soil basically exhibits attenuation characteristics with the vibration frequency.(4)The dynamic stress amplitude is the main factor affecting the dynamic characteristics of high-temperature frozen soil.It determines the shape of the dynamic strain-vibration rate curve and the change trend of dynamic elastic modulus of high-temperature frozen soil;The influence of dynamic characteristics is restricted by the amplitude of dynamic stress,and the result of the influence is more complicated.(5)Under the action of traffic load in high-temperature frozen soil,the hysteretic loop curve exhibits different development patterns affected by the amplitude of dynamic stress.When the dynamic stress amplitude is 30 kPa,the hysteretic loop develops from an ellipse to a parallelogram with the vibration frequency,that is,the high-temperature frozen soil gradually changes from viscoelastic-plastic to viscoelastic under the action of traffic load;when the dynamic stress amplitude is 50 kPa,The hysteresis loop remains elliptical until it reaches the failure criterion;when the dynamic stress amplitude is 40 kPa,the hysteresis loop also transitions from the ellipse to the parallelogram with the vibration frequency,but when the failure criterion is reached,a complete parallelogram is not formed.(6)High-temperature frozen soil exhibits creep deformation under long-term traffic load.Deformation is affected by the amplitude of dynamic stress,showing undecayed creep and non-decayed creep.