Optimization Study For Subgrade Structure Of High-speed Railway In Deep Seasonally Frozen Region Based On Temperature Filed

With the implementation of China’s "One Belt,One Road" strategy and HSR"going out" strategy,and further cooperation between China and Russia in the railway field,more and more railway projects will cross the deep-season frozen soil area.As a bridgehead for Sino-Russian cooperation,Northeast Asia has a unique positional advantage.At present,China has built several high-speed passenger lines in the deep-season frozen soil area,such as Harbin-Dalian HSR,and Harbin-Qiqihar HSR.In recent years,Russia plans to speed up the transformation of the Ussuri Railway,which is the eastern section of the Siberian Railway,and most of the routes planned for the new HSR Moscow-Kazan in Russia will also pass through the deep-season frozen area.Therefore,it is necessary to research the characteristics of climate and frost depth in deep-season frozen soil areas in a wider space area,and then optimize the subgrade structure to ensure the safe operation of high-speed railways.Combining the new Tieli to Yichun passenger transport line project in NortheastChina,through the methods of empirical calculation,theoretical analysis and numerical simulation,this paper makes a comparative study on the calculation methods of the freezing depth in China and Russia,and establishes the high railway basis.After that,the distribution characteristic of subgrade temperature field in deep-season frozen soil area is analyzed,and the effectiveness of "thermal insulation" engineering measures is proposed to optimize the high-speed railway subgrade structure.This study provides a reference for improving the design of high-speed railway subgrade structure in deep-season frozen soil areas.The main results are as follows through research:(1)In the deep-season frozen soil area in Northeast Asia,which center is Northeast China and Russia’s Khabarovsky Krai and Primorsky Krai,the seasonal freezing depth in this area basically obeys the latitudinal distribution law,and the designed freezing depth is between 170～275cm,and it obeys the law of increasing from south to north.The freezing depths of the stations calculated by different methods in China and Russia are similar,which shows the feasibility of the calculation method of freezing depth.(2)The maximum depth of the subgrade soil reaches the maximum at the 7th year,the freeze-thaw process of the subgrade soil has the characteristics of "unidirectional freezing and bidirectional thawing",and the duration of the process is shortened from north to south.The lateral temperature of the subgrade is different.For optimization of the HSR subgrade,the ground temperature state under the shoulder should be improved.(3)The laying of the thermal insulation material XPS on the surface of the subgrade can well block the coldness through the upper surface of the subgrade,and the filling of the insulation protection revetment or setting the widened shoulder on both sides of the subgrade slope can reduce the cold energy from the lateral slope to subgrade body.The insulation revetment structure has better insulation effect than the widened shoulder structure.(4)The composite thermal insulation structure can reduce the freezing depth and freezing rate,shorten the freezing period,at the same time,it is beneficial to reduce the lateral temperature difference of the subgrade soil.It is recommended to lay a composite insulation structure with 10cm thickness XPS insulation material+3.0m high and 2.7m wide insulation revetment in the new section of the new Tieli to Yichun passenger transport line project.This dissertation includes Figure 65,Table 19,and 91 references.