The Law Of Permafrost Plastic Deformation Under Dynamic Load

It is very obvious for the urgency of situation in global warming,self-stablity degradation of permafost,Traffic engineering is vigorously built and regional seismicity is active.The dynamic plastic deformation characteristics of permafrost is the key to understanding the stress response state of the permafrost,and it is also a problem to be solved in the current research direction of permafrost engineering and geotechnical engineering.Since the Qinghai-Tibetan Plateau and its surrounding areas are located at high altitudes,they receive more solar radiation than other low-altitude areas and are also affected by the greenhouse effect at the same time.They are more severely degraded than high-latitude permafrost.Since the Qinghai-tibet plateau and its surrounding areas are seismically active areas,considering the characteristics of static load,dynamic load and the plastic deformation characteristics of permafrost,This paper carried out a different temperature,moisture and confining pressure of indoor triaxial test research,at the same time,combining with the triaxial test of soil physical and mechanical parameters,permafrost field model is established,the plastic deformation characteristics of permafrost and its derivative are studied,Finally,a typical railway embankment in the northern foothill of the Qinghai-tibet plateau is selected.Based on the calculation results of the site model,the plastic deformation characteristics of the roadbed near the subgrade of the typical railway subgrade are revealed.The main achievements are as follows:(1)For silty soil reshape the triaxial test sample preparation,the variety of temperature,moisture and confining pressure under the condition of dynamic elastic modulus,internal friction Angle and cohesive force of physical quantities such as changing with the temperature and moisture,and provides the field model parameters.The results show that the shear strength of permafrost shows a linear relationship with the decrease of temperature,and the sinusoidal relationship changes with the increase of moisture;The dynamic elastic modulus of permafrost shows a linear relationship with the decrease of temperature,and the high temperature unstable frozen soil(-0.5).°C,-1 °C,and-2 °C)are sinusoidal with increasing water content,and low temperature stable frozen soils(-3 °C and-5 °C)are exponential with water content.(2)In the ideal permafrost site under natural earthquake loads,the ideal plastic deformation of permafrost becomes smaller and smaller with the decrease of ground temperature under the same moisture;the plastic deformation of permafrost under the condition of 12% moisture is greater than under the same temperature condition.9% and 15% water content is ideal for plastic deformation in permafrost sites,but ideal plasticity at 15% moisture content at-5°C in permafrost is more than 12% and 9% moisture.Ideal plastic deformation at permafrost sites.(3)Under the action of dynamic loads,the plastic strain of the ideal permafrost site under natural earthquakes obeys the linear relationship of the plastic strain with the decrease of temperature.The results show that the plastic deformation law of permafrost obtained by numerical calculation is consistent with the results of laboratory experiments.The deformation obtained from indoor experiments is larger than that of ideal sites.This shows that the numerical simulation method is used for plastic deformation of permafrost sites under dynamic loading.Regular research is feasible.(4)The typical permafrost roadbed in the Beiluhe area has the largest plastic deformation of permafrost subgrade under the same moisture content.And-1 ? condition,when the moisture of 9% and left and right in the center of the subgrade slope foot plastic deformation are the biggest,up to 1.89 cm;Under the condition of-2?,the plastic deformation of the subgrade of permafrost subgrade was smaller than that of-1?.The results show that under the condition of high temperature unstable permafrost,when the earthquake occurs,it will cause damage to the railway roadbed of permafrost and threaten the safety operation of the train.