| The hydraulic performance of the channel is the main consideration in the construction of anti-seepage lining engineering in unfrozen soil areas,there are numerous kinds of channel cross section forms with good hydraulic performance at present.In seasonally frozen soil areas,because the water in the channel foundation soil freezes under the action of negative temperature in winter,causing the migration of the moisture in the lower part.When the volume of ice crystals and unfrozen water exceeds the porosity,the soil will expand,and the concrete lining structure will be destroyed by squeezing,which affects the normal operation and anti-seepage effect of the channel engineering.Parabolic channels have good water and sand transport capacity and good frost-heaving resistance,having been used in the construction of anti-seepage lining engineering in recent years.Based on the current lack of a comprehensive optimization method that accounts for the hydraulic performance and frost-heaving resistance of the parabolic cross-section structures,this paper established an optimization model considering hydraulic performance and frost-heaving resistance comprehensively to solve the comprehensive optimal section,and carried out analysis and validation through numerical simulation.The main research results are as follows:(1)The calculation methods of parabolic channel section parameters,hydraulic parameters,optimal hydraulic section and practical economic section were summarized systematically.The frost-heaving mechanical model of parabolic channel was established,and the formulas for calculating the frost-heaving force,freezing force,bending moment,axial force and shear force were deduced.(2)Considering parabolic channel hydraulic performance and frost-heaving resistance comprehensively,with the goal of achieving a minimum cross-sectional flow area and a uniform channel section force,taking the flow velocity,the width-depth ratio and the crack resistance of concrete lining plate as constraints,the comprehensive optimization model of the parabolic channel was established.The ? method of linear weighted sum method was used to transform the multi-objective function into a single objective function,and then the weight was allocated to solve the problem.The optimal parabolic channel cross section form was obtained.(3)The optimized model was used to optimize the parabolic channel in the Shijin Irrigation District.Compared with the original channel section in the Shijin Irrigation District,the force uniformity of the optimal section was 23.2% better,the hydraulic performance was1.96% better,and the land use was 12.35% less.The comprehensive optimal section was compared with two typical parabolic channel sections.Compared with the hydraulic optimal section,the maximum positive and negative bending moments of the comprehensive optimal section decreased by 5.6% and 11.89%,respectively,and the force uniformity increased by7.62%.Compared with the practical economic section,the force uniformity and the hydraulic performance of the comprehensive optimal section increased by 1.79% and 0.2%,respectively,and the land use decreased by 4.49%.It showed that the parabolic section calculated by the comprehensive optimization model had both good hydraulic performance and good frost-heaving resistance.(4)Based on the finite element software COMSOL Multiphysics,a three-field coupling numerical model was established.The results of parabolic channel frost-heaving test in Shuguang Experimental Station of Hetao Irrigation District were used to verify and analyze the model.The comprehensive optimization channel was simulated using the numerical model after validation,and compared with the calculation results.The results showed that the outer surface of the channels in the central channel bottom reached the maximum stress,the inner surface of the channels near the bottom 1/3 of the slope reached the maximum stress.The calculated results were in good agreement with the simulation results,indicating that the comprehensive optimization model was reasonable and feasible,which could be used as a reference and guide for the selection and design of parabolic channels in seasonally frozen soil areas. |
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