Study On Frost Heave Characteristics Of Harbin-Mudanjiang High-speed Line Subgrade

China's high-speed railway industry has developed rapidly,and several high-speed railways are in operation or construction in seasonal frozen areas.Although high-speed railways have made great progress in technology compared with ordinary railways,they still suffer from frostbite every year,among which frostbite is relatively common.In view of this problem,relevant scholars have conducted a lot of research and put forward many theories and countermeasures.Although the problem has been improving,it has not been completely solved.Based on the previous research data,this paper systematically studied the frost heaving characteristics of the railway subgrade of Harbin-Mudanjiang high-speed line by taking the subgrade filling of typical sections of Harbin-Mudanjiang high-speed line subgrade as the object and carrying out the soil frost heaving test in the laboratory,combined with the finite element analysis method.1)The investigation and research data of roadbed frost damage in the seasonal freezing regions of northeast China,north China and northwest China were collected and sorted out.The investigation shows that frost heave of railway subgrade is a typical disease form,and the development rule,location and time of frost heave are analyzed.2)Based on Harbin-Mudanjiang high-speed railway line the temperature,precipitation and other climatic characteristics of this region are analyzed.The physical indexes of the filler,such as particle size distribution,particle density,liquid plastic limit of fine soil,maximum dry density and optimal moisture content,were obtained by laboratory test.The shear strength and compressibility of the fillers were analyzed by direct shear and compression tests.The shear strength of the filler in the optimal moisture content state was less than that in the natural state,and the internal friction Angle was larger in both states,and even exceeded 45 in the natural state.The packing is low compressibility soil under the optimal moisture content state The a-p and es-p curves of the filling are both fluctuating.3)In order to analyze the frost heaving characteristics of the filler,a test device for soil frost heaving was developed.The test equipment includes: specimen model,cooling system,water supply system,temperature monitoring system,deformation monitoring system,etc.The freezing process of subgrade was simulated,and the frost heave test was carried out under closed system(no water replenishment)and open system(water replenishment).4)For different types of fillers(typical road subgrade fillers,soil samples with a fine soil content of 8% and soil samples with a fine soil content of 16%),the frost heaving test of the closed system with different water content is carried out.The temperature change of soil samples will go through five stages of rapid cooling,slow cooling,slow freezing,rapid freezing and freezing stability.With the increase of moisture content,the time of slow freezing period is longer.The frost heave increases with the increase of moisture content.5)For different types of fillers(typical road subgrade fillers,soil samples with fine soil content of 8%,and soil samples with fine soil content of 16%),the freezing test under open system was carried out under the condition of the same initial moisture content.The frost heaving deformation and temperature change of different fine particle contents were analyzed.The results show that the higher the content of fine soil,the larger the frost heave.Under the same condition,the amount of frost heave in the open system is larger than that in the closed system.The lower the temperature is,the faster the sample freezes.The frost heave amount of the sample is different at different temperature.6)The temperature field and frost heave deformation of subgrade at different time of typical subgrade section of Harbin-Mudanjiang high-speed railway line with different water content were simulated by finite element method.The results show that the rapid development period of frost heave is from November to January,the stable period of frost heave is from January to march,and the thawing period of frost heave is from march to may.The maximum frost heave deformation of roadbed top appeared in February.The frost heave deformation of slope top on both sides was enlarged in the center of roadbed,and the deformation on both sides of roadbed was asymmetric.