路基土体“时变覆盖效应”的数值模拟分析  

NUMERICAL SIMULATION AND ANALYSIS OF ‘TIME-VARYING CANOPY EFFECT’ OF MOISTURE TRANSPORT IN SUBGRADE SOIL

作　　者：宋二祥[1] 仝睿 罗爽[1] 李鹏[1] SONG Er-xiang;TONG Rui;LUO Shuang;LI Peng(Key Laboratory of Civil Engineering Safety and Durability of the State Ministry of Education,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学土木工程系土木工程安全与耐久教育部重点试验室

出　　处：《工程力学》2019年第8期30-39,共10页Engineering Mechanics

基　　金：国家重点基础研究发展计划(973计划)课题项目(2014CB047003);国家自然科学基金项目(41272279,51778339)

摘　　要：针对寒区铁路路基浅层土体冻结状况变化时使其透气透水性(覆盖条件)改变,进而影响其内水分迁移、集聚乃至冻胀的现象,提出“时变覆盖效应”这一概念。基于非等温水热气耦合运移模型以及刚性冰模型,建立了对路基土体内水分迁移、冻胀发展进行模拟的数学模型。对时变覆盖效应下水分迁移与冻胀的一维问题进行模拟,揭示了时变覆盖效应下路基土体水分蒸发、迁移的规律。模拟结果显示,时变覆盖效应下,土体的冻胀量较全时完全覆盖条件下相比较小,但仍有可能对铁路设施造成危害。此外,该文还对土性、温差大小以及初始含水量对时变覆盖效应的影响进行了分析。The top cover condition of railway subgrade may change from evaporation boundary to sealed boundary after frozen in winter time,which will influence the transportation of moisture up from the bottom and its accumulation beneath the frozen surface.The concept of ‘time-varying canopy effect’ is introduced and a mathematical model is established for its analysis based on the non-isothermal coupled water and heat migration model as well as the rigid ice model.Water migration in one-dimension soil column is simulated considering constant canopy effect and ‘time-varying canopy effect’ respectively.Simulation results show that the frost heave under time-varying canopy conditions is smaller than that under constant canopy conditions,but it may still be large enough to disturb the normal performance of the railway.The influences of soil type,temperature difference and initial water content on the ‘time-varying canopy effect’ are also discussed.

关 键 词：时变覆盖效应 水分迁移 蒸发 冻胀 数值模拟 

分 类 号：TU445[建筑科学—岩土工程]