北方灌区混凝土衬砌渠道断面优化及参数分析

人工明渠是中国北方灌区采用的主要输水方式。合理的渠道断面参数计算是水利计算中的重要环节。因此,合理的模型与较高精度的计算方法是求解渠道断面的关键。然而传统灌区混凝土衬砌渠道断面优化设计仅从最优水力断面角度出发,考虑单一水力要素,而忽视了渠道冻胀安全以及工程造价的问题。该文建立了以最优水力断面、工程造价最小为目标,满足混凝土衬砌渠道冻胀要求的数学模型。根据模型非线性的特点,利用自适应粒子群优化算法,对混凝土衬砌渠道梯形断面结构进行优化,选用自适应粒子群算法可以很好地克服算法陷入局部最优解的问题。建立的模型将混凝土衬砌量与工程占地最小作为目标函数优化。优化结果在最佳水力断面基础上,满足边坡稳定与工程量最小。最后将模型应用于黑龙江依兰县倭肯河灌区学兴干渠,分析了渠道边坡系数、渠底宽和渠道水深对目标函数的影响规律。优化结果表明,模型计算所得渠道工程占地减小1.5%,混凝土衬砌量减小1.8%。各个参数中,边坡系数对目标函数影响较大。混凝土衬砌厚度由土壤性质、冻结力大小所决定。该研究成果为提高寒区混凝土防渗渠道优化设计水平及灌区运行效益提供了理论依据。

Optimization and parameter analysis for channel cross section with concrete lining in northern irrigation district

Abstract: Artificial open channels are the major conveyance systems to deliver water. Computation of parameters of channel cross section is an important task in hydraulic design of open channels. From a hydraulic engineering perspective, it would be prefer to have an optimal method with reasonable mathematical model and high accuracy for designing the parameters of channel cross section. However, the optimization method of the channel cross section in northern Irrigation District with concrete lining only considers the reliability under single hydraulics conditions, while ignoring the safety of frost heaving and the economy. To optimize trapezoidal cross section structure with the concrete lining accurately, a mathematical model based on optimal hydraulic section, economy, and safety of frost heaving is solved by adaptive particle swarm optimization (APSO). The APSO is presented to overcome the problem of premature convergence and local optimal in conventional particle swarm optimization (PSO). With a reasonable assumption combined with the basic theory of mechanics, the constrained optimization model is propounded, which considers the thickness value of channel concrete slab simultaneously with the objective of cost minimization. The optimized channel section not only satisfies the optimal hydraulic cross section but guarantees the safety and stability of the side walls so that both the amount of the concrete lining and the land acquisition are optimized. Finally, the Xuexing main channel of Wokenhe Irrigation District in Heilongjaing Province is taken as an example to analyze the effects of design parameters, such as channel slope, width of channel bottom, height of channel on the objective function. The result shows that the parameters obtained by the APSO can minimize the lining cost and the land occupation under the condition of satisfying the optimum hydraulic section. Comparing the 12 continuous channel sections based on wetted perimeter, the reductions of the lining amount and the land occupation were 1.8% and 1.5% respectively with the low flow errors. For parameters, the optimum is less sensitive to the increase in bed width and more sensitive to the increase in side slope obviously. When the values of width and height of the channel increase, the objective function increases. The value of lining thickness is a comprehensive reflection of soil quality, negative temperature and status of moisture; thereby the objective function can be solved provided that freezing forces is determined according to the practical experience or experiment. The results obtained by APSO approach are satisfying and the method can be used reliably for the design of artificial open channels. The research can improve the level of concrete seepage channel optimization in cold region and provide a scientific basis for enhancing operation benefit in irrigation district.