多年冻土区路基U型水沟热力耦合理论分析及现场试验

Theoretical Analysis of Thermo-mechanical Coupling and Field Test on U-type Canal of Embankment in Permafrost Regions

针对青藏铁路多年冻土区路基坡脚U型排水渠道的冻胀病害,采用热力耦合的有限元方法对U型排水渠道的温度场和应力场进行数值计算,分析U型排水渠道周围土体的温度场和渠道所受水平冻胀力的分布特点及渠道冻害产生的原因,并对提出的防治措施进行现场验证。结果表明,寒季在U型排水渠道附近将出现二维冻结区域,产生的水平冻胀力可导致其破坏;渠道所受水平冻胀力沿埋深呈不均匀形状分布,中段较大,两端较小;渠道周围换填10cm厚非冻胀填料可有效减小水平冻胀力,使其稳定性明显提高。

In response to the frost damages of U-type canal of the embankment of Qinghai-Tibet Railway in permafrost region,the temperature and frost heave stress fields of U-type canal were simulated through coupled thermo-mechanical FEM theory,to analyze the distribution characteristics of temperature field of soils surrounding the U-type canal and horizontal frost heaving force of the canal,and the causes of frost damages.Field verification was conducted on the prevention and control measures proposed.The computational results showed that a 2-D frozen zone would appear near the U-type canal in winter and the consequent horizontal frost heave force would cause the failure of the canal.The horizontal frost heave forces distributed unevenly along the depth of U-type canal,with higher horizontal frost heave forces occurring at 1/2~2/3depth of U-type canal and lower frost forces on top and bottom of the canal correspondingly.Replacing the soil along the U-type canal with 10cm-thick non-frost-heave material can effectively reduce the horizontal frost heaving force and significantly improve the stability of the canal.