基于部分保温法的渠道保温板厚度计算与数值模拟

保温板是北方渠道常用的保温材料，其铺设厚度一般通过经验或全部保温法的热工计算确定，工程造价较高。该文以聚苯乙烯泡沫板为例提出了部分保温法，分析了其合理性和适用条件之后，基于热阻等效原理给出了其计算方法，同时选取新疆车排子西干渠进行部分保温法保温板厚度设计，并与全保温法计算量进行比较。结果表明：部分保温法比全保温法降低了19%的工程造价。最后利用ANSYS有限元程序对原渠道和部分保温渠道进行热力耦合数值模拟。数值分析表明：部分保温渠道的最大冻胀量为1.35 cm小于设计允许值2 cm，满足抗冻胀要求，部分保温法是可行的；其冻胀量、冻胀力不但分布更加均匀，且被大幅削减，其中阴坡被削减达80%以上。

Thickness calculation and numerical simulation of insulation board for canal using partial insulation method

Insulation board is a widely used canal insulation material in the northern part of China. Its thickness is usually determined by experience or by thermal calculations based on the total-insulation method. A canal, as a long line project, normally requires a huge amount of insulation boards. Subtle differences in laying thickness have a great influence on the project budget. Three main considerations include: 1) the thawing settlement reduction ability of the canal lining structure allows certain frost heave displacement; 2) frost heaving is bidirectional, which will cause compression deformation of soil under the freezing front; 3) insulation board may postpone the frost period of the canal foundation soil and weaken the freezing strength through delaying the freezing front and affecting moisture migration. Therefore, a partial-insulation method is reasonable and feasible. A saturated layer underlying the insulation board may develop using the partial-insulation method during the freeze-thaw season, which may cause canal stability problems. So the applicable conditions of the partial insulation method are presented, including the safe slope ratio, setting toothed walls, or a rigid bottom under the canal slope. A concrete trapezoidal canal is not suitable for the partial insulation method. Insulation board, using both the total insulation method and the partial insulation method, was designed and compared with the actual laying thickness in the west main canal of Chepaizi in Xinjiang of China. The results indicate that the project cost associated with the partial insulation method is reduced by 19%. The general-purposes finite element software ANSYS was applied to simulate the thermal-mechanical coupling process before and after the insulation board was laid. When actual mechanical parameters were not available for the concrete lining structure and frozen soil under different temperatures, this paper adopted general parameters that are widely used in other articles. After the thermal-mechanical coupling simulations were conducted, the equivalent linear expansion rates of frozen soil were obtained by inverse computation of measured frost heaving. Finally, the equivalent linear expansion rates were used to simulate the canal thermal-mechanical coupling process before and after insulation board was placed, and the frost heaving, frost-heave forces, and uneven frost heaving coefficient were extracted. The uneven frost heaving coefficient was defined as the quantity difference of frost heaving between two points dividing the distance. Numerical analysis indicates that the maximum amount of frost heaving of laid insulation board canal is 1.35 cm less than the allowable value (2 cm), which proves that the partial insulation method is safe and feasible. Meanwhile, the frost heaving quantities and frost-heave forces of the lining structure are not only apparently reduced, but also more uniform. Moreover, the reduction in the shady slope is 80%, and the uneven frost-heaving index of the canal base dropped 94%.