Study On Numerical Regression Model Of Shear Strength Of Frozen Soil With Application To Frozen Ground Engineering

Frozen soils mainly distribute at north-central region and Qinghai-tibet plateau area of China and are classified into permafrost frozen soil and seasonal frozen soil,which are composed of soil grain,water,ice and gas, and its characteristic of the cycle of freezing in winter and thawing in summer causes the complexity of the frozen soil.There is a large number of civil engineering construction in seasonal frozen areas of China and the lack of organization of mechanical property of frozen soil could result in potential engineering risk.Based on Mohr-Coulomb criteria,this paper focuses on the relations between shear strength parameters of frozen soil and other factors such as temperature, water content, freeze-thaw cycles,confining pressure and dynamic load and establishes fitting formula of frozen soil shear strength for different soils. Furthermore,the embankment stability is evaluated by COMSOL Multiphysics based on hydrothermal field in the background of the Ha-Qi high speed railway.The main research work and originality covers the following aspects:1.This paper reviews for frozen soil shear strength systematically and summarizes the changing law of frozen soil shear strength with temperature, water content, confining pressure,freeze-thaw cycles and dynamic load,results show that,the lower the temperature,the higher the shear strength becomes; Frozen soil shear strength decreases with increasing water content when the initial water content at high level,but increases at low level;Frozen soil shear strength gradually reduces with the freeze-thaw cycle,but begins to stabilize after a certain number;The relationship between confining pressure and shear strength is parabola; The strength is influenced by combined actions of factors of temperature, confining pressure,frequency under dynamic load.2.The mathematical expressions of shear strength parameter and each affecting factor is concluded for different kinds of soils by the methods of summary and fitting based on a large number of experimental data,which are analyzed for the applicability.3.On the background ofHa-Qi high speed railway.the frozen soil hydrothermal field is numerical simulated by COMSOL Multiphysics and the following conclusions are drawed,frost-heave depth and capacity at low temperatures is calculated and frost-heave capacity variation is found to lag behind the surface temperature variation; Taking hydrothermal fields of different months as the initial state and applying established mathematical expressions to different embankment soil layers,this paper analyses the embankment stability at different time points, results indicate that, the lower the temperature,the higher the safety factor becomes; Stability safety gradually reduces with the freeze-thaw cycle,but begins to stabilize after a certain number.This paper studies on the changing relationship of frozen soil shear strength with external factors systematically,and using the finite element software,some results are verified. It turned out that the conclusions drawed from the paper are valuable.