考虑基土不均匀冻胀的梯形渠道混凝土衬砌弹性地基梁力学模型

为了探究寒区高地下水位引起渠道基土不均匀冻胀对梯形渠道混凝土衬砌冻胀的影响作用,该研究在前期提出的弹性地基梁模型基础上,将基土不均匀冻胀对边坡衬砌板的作用等效为作用在衬砌板上的荷载,给出在边坡衬砌板在基土发生不均匀冻胀的情况下其冻胀量,冻胀反力,弯矩和剪力的计算方法。以甘肃省高液限土壤,地下水位5 m地区的边坡系数为1的渠道为例,探究不同边坡衬砌板长度和不均匀冻胀基土之间的相互作用。结果表明,边坡衬砌板长度每增加1 m,冻胀反力最大值增大142%,弯矩最大值平均增大223%。同时,弯矩最大值点会从原来的距坡脚1/3左右处向坡脚偏移。因此,在寒区的高水位地区进行渠道设计的过程中,建议尽可能设计为宽浅式横断面,以减少由地下水引起的基土不均匀冻胀对渠道衬砌板的影响。同时,以边坡衬砌板长度为4 m为例,探究了基土均匀冻胀和不均匀冻胀对边坡衬砌板影响的差异,得出基土不均匀冻胀的冻胀反力最大值和弯矩最大值,分别比基土均匀冻胀大264%和170%。因此,在寒区高水位地区进行渠道抗冻胀衬砌设计时,宜按基土非均匀冻胀弹性地基梁模型计算。

Frost heave mechanical model of concrete lining trapezoidal canal considering nonuniform frost heave of foundation soil based on elastic foundation beam theory

In areas with high groundwater levels in cold regions, due to the different distances between the calculation points of the canal slope lining slab and the groundwater level, the frost heave of the foundation soil under the slope lining slab presents a different distribution from the canal top to the canal bottom. The slope lining slab has a large amount of frost heave in the bottom area of the canal, and a small amount of frost heave in the canal top area. To explore the effect of nonuniform frost heave of foundation soil caused by high groundwater level in cold areas on the frost heave of concrete lining trapezoidal cannal, the effect of nonuniform frost heave on the lining slab was equivalent to the load acting on the lining slab based on the elastic foundation beam model proposed earlier. The calculation methods of deflection, frost heave reaction force, bending moment and shear force were given in the case of nonuniform frost heave of the canal foundation soil. Taking the canal with slope coefficient of 1 and groundwater level of 5 m as an example, this canal was surrounded by the high liquid limit soil in the Gansu Province. The interaction between the different lengths of slope lining slabs and the nonuniform frost heave foundation soil in the process of frost heave was explored. The results showed that for every 1-m increase in the length of the slope lining slab, the maximum value of frost heave reaction force at the slope foot increased by 142%, and the maximum value of bending moment averagely increased by 223%. Meanwhile, the position of the maximum value of the bending moment moved from the original one-third of the slope foot to the slope foot. Therefore, it was recommended that the cross section should better be designed as wide and shallow as possible in order to reduce the influence of nonuniform frost heave of the foundation soil caused by the groundwater level on the canal lining slabs. For trapezoidal canal with narrow and deep cross-sections, it was recommended to set joints within one-third to one-fifth of the length of the slope lining slab from the slope foot to release the frost heave force. The specific location should be comprehensively considered and determined according to the groundwater level, the length of the slope lining slab and the slope coefficient. Meanwhile, taking the slope lining slab length of 4 m as an example, the difference between the effects of nonuniform frost heave and uniform frost heave on the slope lining slab was explored, and maximum frost heave reaction force and maximum bending moments were 264% and 170% greater than the uniform frost heave of the foundation soil, respectively. Therefore, when designing the anti-freeze-heave canal lining slabs in the cold area with high groundwater, the calculation should be based on the nonuniform frost heave elastic foundation beam model. This study can guide the design of anti-frost heave of canal lining slabs in cold areas with high groundwater.