兰新高铁军马场至民乐区间路基冻害原因分析及整治措施

兰新高铁兰州铁路局管段2014年冬季无砟轨道精测精调时发现K2 005~K2 030区间的轨道平顺性不能满足列车运营要求,其原因系路基发生冻胀所致。通过现场调查、试验研究、数据分析得出冻胀原因,并提出整治措施。(1)基床底层填料多为B组粗颗粒填料,其粒径小于0.075 mm的细粒含量为10.96%~21.46%,填料在水分、低温等不利条件作用下会发生冻胀或微冻胀造成高铁路基发生冻害;(2)该区段雨(雪)水、农田灌溉水等水资源丰润,水分将从路基边坡、天然护道、排水沟两侧等进入路基,造成路基体内水分较高,给冬季负温作用下发生冻胀提供了有利条件;(3)因路基填料与天然地基土热力参数的差异性,加之该区间海拔高、冬季温度低且低温持续时间长等环境因素影响,路基冻结深度达到2.5 m以上,大于该区土壤标准冻结深度;(4)由于该线已开通运营,通过修建渗水盲沟、反压及保温护道、隔水墙等措施消除或减小冻胀变形,以保证高铁正常运行。

Cause Analysis and Treatment Measures of Subgrade Frost Damage in Junmachang to Minle Section of Lanzhou-Xinjiang High-speed Railway

In the winter of 2014,it was found that the track regularity could not meet the train operating requirements in the section of K2 005 to K2 030 of Lanzhou-Xinjiang high-speed railway in the territory of Lanzhou Railway Bureau. The irregularity was caused by subgrade frost heave. With field investigation,experimental research and data analysis,the causes are identified and treatment measures are provided.( 1) Where the bottom of roadbed is compacted with B class filler with 10. 96% ~21. 46% of particles less than 0. 075 mm,the filler in place would generate frost heave,resulting in subgrade frost damage subject to adverse moisture and temperature.( 2) In the section,surface water permeates into subgrade from slope and drain ditches,resulting in high moisture content in subgrade and constituting conditions for subgrade heave in winter when temperature drops bellow zero.( 3) Due to the difference of the thermal parameters between the subgrade filler and the natural ground soil,the high altitude,low negative temperature and long duration,the subgrade freezing depth is more than 2. 5 m,exceeding the standard freezing depth in this region.( 4) Based on the fact that this railway is already opened for operation,seepage blind ditch,back pressure,thermal protection road,water resisting wall and other measures are employed to eliminate or reduce deformation for normal operation of the high-speed railway.