寒区弧底梯形衬砌渠道冻胀破坏的尺寸效应研究

Size effect on frost heave damage for lining trapezoidal canal with arc-bottom in cold regions

为探明地下水埋深、冻深及渠深对冻土地基上弧底梯形衬砌渠道冻胀破坏的影响规律,依据毛细理论将渠道冻胀分为封闭系统、半开放系统和开放系统;基于冻土水热力三场耦合理论,利用多场耦合软件COMSOL Multiphysics模拟研究了30组不同尺寸衬砌渠道的冻胀位移场和应力场。结果表明:规范建议的衬砌厚度内,渠道规模越大越窄深、冻深越大、地下水埋深越浅,则衬砌渠道冻胀破坏越严重。封闭系统,中小型衬砌渠道为渠底中心下表面拉裂,大型渠道为渠底中心下表面和距渠顶2/3坡长处上表面拉裂;半开放系统,中小型渠道为渠底中心上表面拉裂,大型渠道为渠底中心上表面和坡脚下表面拉裂;开放系统,小型渠道为渠底中心上表面拉裂,中型渠道为坡脚上表面拉裂,大型渠道为渠底中心下表面和距渠顶2/3坡长处上表面拉裂。该研究揭示了渠道衬砌冻胀破坏的尺寸效应,对弧底梯形衬砌渠道抗冻胀设计及衬砌结构合理设缝具有指导意义和定量化参考。

In order to find out the influence of groundwater table, frozen depth and canal height on the frost heave damage for lining trapezoidal canal with arc-bottom on the frozen soil base,a classification system for frozen soil was described as closed system, semi-open system and open system in terms of themaximum capillary rise. Based on the thermal-moisture-mechanic coupled theory for frozen soil,30 sets oflined canals with different sections were performed with the assistance of COMSOL Multiphysics software.The results of calculated displacement field and stress field show that within the range of the thickness oflining suggested by standard, the larger the scale of the canal with narrower and deeper section, and thelarger the frozen depth and the more shallow the groundwater table are, the more serious damage of frostheave for lining canal will be. For the closed system,the small and medium size canals can be cracked atthe center on the lower surface of the lining canal bed, while the large-size canals can be cracked bothat the center on the lower lining surface of the canal bed and at the 2/3 height from the top of canal onthe upper surface of the lining canal slope. For the semiopen system, small and medium size canals canbe cracked at the center on the upper surface of the lining canal bed, while large-size canals will becracked both at the center on the upper lining surface of the canal bed and on the lower surface of the lin-ing canals slope foot. For the open system, small size canals can be cracked at the center on the uppersurface of the lining canal bed,medium size canals can be cracked on the upper surface of the lining canal foot, while the large-size canals can be cracked both at the center on the lower lining surface of thecanal bed and at the 2/3 height from the top of canal on the upper surface of the lining canal slope. Theresults revealed the size effect on frost heave damage for lining canals, providing a guiding significanceand a quantitative reference for the anti-frost heave design and reasonable joints of lining construction for lining trapezoidal canal with arc-bottom.