深季节冻土区路基防冻胀道砟碎石排水盲沟热状况的数值分析

用透水土工布包裹道砟碎石填筑的截排水纵向盲沟, 是哈尔滨-大连高速铁路(简称哈大高铁)在大开挖路堑段采用的重要的防冻胀工程措施. 由于碎石层在顶部温度较低时, 其中发生对流换热过程而强化对其下部土体的降温作用, 可能导致盲沟底部冻结而影响其防冻胀效果. 通过数值仿真软件分析了排水盲沟的温度状况, 结果表明: 对于哈大高铁的气温环境, 在不考虑积雪影响的条件下, 将发生盲沟底部排水管冻结积冰, 影响纵向盲沟防冻胀效果的问题. 在盲沟顶土层中加设0.1 m保温板能够提高盲沟底部的最低温度, 推迟起始冻结时刻, 缩短冻结时长, 但不能完全避免盲沟底部排水管的冻结问题. 在有表层保温板的条件下, 在盲沟底部换填砂层虽然不能提高盲沟碎石层的温度, 但却能有效提高盲沟底部的温度. 复合措施可以有效解决盲沟底部冻结的问题.

Numerical analysis on the thermal regime around an anti-frost ballast subdrain within roadbed in deep seasonally frozen regions

An important anti-frost engineering measure applied on deep cut sections of the Harbin to Dalian High Speed Railway is longitudinal subdrains constructed with ballast layer wrapped with permeable geotextile. Convective heat transfer process, which takes place when the top temperature of the ballast layer is lower, will strengthen the cooling effect on the bottom of the subdrains, and affect its anti-frost effect. The thermal regime of the subdrain and the effect of engineering measure against frozen damage to the subdrains are analyzed by using numerical simulation software. It is found that the bottom of the subdrains will freeze up, and its anti-frost effect will be affected under the environment temperature along the Harbin to Dalian High Speed Railway and ignoring snow cover. Adding an insulation board of 0.1 m thickness in the soil above the subdrains can raise the minimum temperature at the bottom of the subdrains, postpone the starting time of frost and shorten the frozen period, but cannot completely avoid the subdrain frost. The temperature of the ballast will not increase apparently by replacing the lower part of the ballast with sand, in addition to an insulation board of 0.1 m thickness added to the top of the ballast, but it can effectively raise the temperature at the bottom of the subdrains. This compound measures are able to satisfactorily solve the frost problem of subdrains.