The Research Of Temperature Field Distribution Characteristics Of Culvert In Deep Seasonally Frozen Region

In railway subgrade engineering,the culvert not only improves the transverse drainage conditions,but also forms the natural wind channel in the subgrade body in seasonally frozen region,which makes the influence factors and boundary conditions of the roadbed-culvert transition section roadbed in the freezing and thawing process generate obvious changes compared with the line subgrade.Therefore,the frost damage often appeares in the roadbed-culvert transition section of subgrade in deep seasonal frozen region.The domestic and international scholar have done a lot of researches about the temperature field of culvert and frost damage problem early in permafrost regions,but less researches on the temperature field of culvert in deep seasonal frozen region.With reference to the second bid project of Huo-Bo Railway in building in seasonally frost region,the study about the temperature field distribution and the frost damage prevention of culverts was carried out through the field test and finite element numerical simulation method about the typical culvert section,considering the actual situation and the local climate and hydrological conditions.The results are as follows:(1)The distribution rule of temperature field and wind field in the hole of the culvert has been mastered through the field monitoring of typical section of culvert,which will provide the basis for antifrozing design and construction of culverts.Test results show that: in the winter,the temperature field from the mouth of the culvert to subgrade in the outer wall of culvert increases with increasing depth,and all in minus temperature condition;each measuring point temperature in the tunnel of culvert is closed to atmospheric temperature and the lower temperature measuring point tend to appear at the center of the culvert.the maximum wind speed in the tunnel of culvert often appear in the center of the clearance section,and the speed in the center of culvert tends to small.(2)The impact of the dry wet environment outside has bigger effects to the soil moisture content in the top surface of the culvert than the internal soil.In winter,The soil begins to freeze when the temperature in the top of the culvert drops to minus temperature state,while the soil moisture content increases due to the moving moisture from the subgrade body to the top of the culvert.(3)The temperature field in low temperature environment was simulated through the finite element software.The results show that: the side soil temperature of the culvert increases with increasing depth,and the positive temperature turns to negative temperature after reaching a certain depth.The soil temperature from the subgrade surface to the top of culvert decreases with increasing depth,and the minimum occurs in the top of culvert.(4)The design that 10 cm thick insulation is attached to the side of the culvert is optimal through the numerical simulation towards the different positions and thickness of the insulation layer of the culvert,combining with the convenience of field construction.