基于TCR传热原理的混凝土复合保温衬砌渠道防冻胀效果研究

Anti-frost heave effect of lining channel with concrete composite insulation based on TCR principle

中国北方寒冷地区广泛采用保温措施进行渠道防冻胀,在苯板保温防冻胀设计中铺设厚度一般根据半理论半经验确定,并没有考虑衬砌板与保温板接触热阻及交错布置对保温性能与削减冻胀的影响。该文依据固体材料接触热阻(thermal contact resistance,TCR)原理与压力相关的传热本构模型,提出了混凝土复合保温衬砌新型式。通过ABAQUS有限元软件采用热力耦合模拟将其与普通型式的苯板保温渠道进行比较。结果表明:与普通保温衬砌渠道相比,外界负温时,复合保温衬砌的保温及消减冻胀力效果显著。理论上复合保温衬砌冻胀量消减40%以上,法向冻胀力减少66%,切向冻结力减小58%。对寒区衬砌渠道保温防冻胀设计提供了相应的理论参考。

In cold regions of northern China, the anti-frost heaving measures of lining channels were widely used. In the design of anti-frost heaving benzene insulation board, laying thickness was generally determined on the basis of semi-theoretical and half-experience analyses. However, it did not consider the thermal contact resistance（TCR） between canal lining and insulation board, as well as the influence of the staggered arrangement on thermal-insulating performance and anti-frost heave. Therefore, original canal insulation model was too idealistic. Based on the principle of TCR of solid materials and the stress-related heat transfer constitutive model, the paper presented a new concrete composite insulation lining. In order to explore the effect of anti-frost heaving capability and the anti-frost heaving mechanism, taking a trapezoidal channel in Altay irrigation area of northern Xinjiang as the simulation object and considering the impact of the frost heaving, the prototype channel model was set up. Based on this model, the anti-frost heaving effect of the EPS（expanded polystyrene） thermal insulation board on the channel was analyzed. The temperature field, stress and displacement field were calculated and analyzed by the thermo-mechanical coupling field finite element method. The composite thermal-mechanical simulation was used to compare the new one and the ordinary benzene insulation board by means of the finite element software ABAQUS. Simulation results showed that for the temperature field, the zero degree isotherm in the composite insulation lining channel soil was higher than that in the channel with EPS insulation board, and the maximum difference was nearly 20.3 cm. The concrete composite insulation lining could not only block the conduction of the negative temperature outside and improve the temperature of the soil, but also reduce the freezing depth of the soil and improve the anti-frost heaving ability effectively. For the displacement field, the distribution of the frost heaving amounts in the channel with EPS insulation board was even. Among these models, the frost heaving amounts of the channel with the composite insulation lining could be reduced by 71%, 46% and 40% respectively compared to the prototype channel and the other 2 models, which showed that the anti-frost heave effect was obvious. Similarly, the frost heaving force that functioned on canal lining was analyzed and compared, mainly including normal frost heaving force and tangential freezing force. In the stress analysis of flexible EPS insulation board composite insulation lining, the friction between concrete lining plate and foundation soil was reduced as the concrete lining did not contact with the soil. The EPS board between concrete lining and foundation had certain flexibility, and when the frost heaving of canal foundation occurred, it would release stress and distribute channel lining stress evenly. Compared with the prototype channel, the distribution of normal and tangential freezing force of the concrete composite insulation lining channel tended to be uniform, which improved the stress of the channel lining greatly. However, in terms of reducing the normal and tangential freezing force, the channel with the composite insulation lining was more obvious than the other 2 types of insulation linings in shady slope, and the frost heaveing force in this model could be reduced by 60% or more. Compared with the prototype channel and the other 2 types of channels, the normal frost heaving force in this model in shady slope was decreased by 91%, 78% and 66% respectively. In the sunny slope, the normal frost heaving force in the channel with the composite insulation lining was evidently decreased compared with the other 3 types. For the channel with the composite insulation lining, the tangential freezing force in shady slope about 1.0 meter from the top of the channel was decreased by 91%, 63% and 58% respectively compared with the prototype channel and the other 2 types of channels. Therefore, the composite insulation lining has stronger heat insulation and anti-frost heave capability than the ordinary insulation lining in the negative temperature. The research provides the theoretical reference for the design of the thermal insulation lining channel in cold regions.