Subgrade Frost Damage Remediation Technology For Operation Railway In Seasonally Frozen Ground Zone

Lanxin railway is an important component of the railway net in northwestern China. The capacity is more than90million ton, and the speed of the train is up to160km/h in parts of the sections. Wuwei works section, Lanzhou railway administration, takes charge of398km Lanxin railway. The section between Jiling and Malianjin passes through the seasonally frozen ground zone above elevation of2100m. The lowest temperature is about-30℃in winter. The deepest frozen depth is1.43m. The average precipitation is around200mm annually, and most of the rainfall is in summer and fall. The subgrade frost damage begins from November, and lasts to May next year. During the6months, frost damage changes the profile of the railway line frequently; increases the workload of the maintenance and the cost. The quality of the railway decreases, the traffic safety is endangered, as well as the normal railway organizational order is disturbed.Therefore, Lanzhou railway administration combining with research institutions controls the subgrade frost damage by different measures in seasonally frozen ground section. Based on the data of the geological, hydrological, meteorological and frost damage collected during the last four years, the physical characteristics and the trends of the subgrade frost damage in seasonally frozen ground zone are analyzed. According to the investment plan, the following subgrade frost damage remediation tests were conducted: subgrade surface closed by geomembrane, drainage pores, as well as seepage wall combining with drainage pores. The above tests were conducted with the operation of the railway transportation. Based on the monitored subgrade frost damage trends during the whole freeze-thaw period, the following conclusions were obtained:1. Due to the water content in the subgrade is large during the subgrade surface construction by geomembrane, and the geomembrane is not closed tightly, the subgrade frost damage remediation results are not significance.2. The water content in the subgrade ground decreases before frost by the one layer drainage pores with spacing of1.0-1.5m. The ground around pores is frozen advanced. It can control the development of the subgrade frost heave. The drainage pores remediation results are significance for low subgrade frost damage along Lanxin railway.3. Seepage wall decreases the water content in subgrade ground with some degree depth around the drainage pores before frost. It drain the water in the subgrade ground. The seepage wall with drainage pores remediation results are significance for frost damage.Based on the project of the subgrade frost damage remediation, the following were analyzed and understood:the reason of the subgrade frost damage, the failure feature of the freeze heave, and the freeze law. The research method for the subgrade frost damage in seasonally frozen ground zone was established. The three types of subgrade frost damage remediation in seasonally frozen ground zone were analyzed and evaluated. During the daily maintenance, it will improve the remediation of the subgrade frost damage in seasonally frozen ground zone efficiently, decreases the disturbing of the railway operation due to the subgrade frost damage, make sure the safety of the railway transportation.