排水沟附近农田潜水蒸发计算的渗流力学方法  

A Seepage Mechanics-based Method for Calculating Phreatic Water Evaporation on Farmland near a Drainage Ditch

作　　者：林飞[1] 任红蕾 韦婷[1] 陶月赞[1] LIN Fei;REN Honglei;WEI Ting;TAO Yuezan(College of Civil Engineering,Hefei University of Technology,Hefei 230009,China)

机构地区：[1]合肥工业大学土木与水利工程学院,安徽合肥230009

出　　处：《地球科学进展》2022年第5期484-495,共12页Advances in Earth Science

基　　金：清华大学水沙科学与水利水电工程国家重点实验室2020年度开放基金项目“数值模拟在重金属污染场地精准调查设计中的应用研究”(编号:sklhse-2020-D-06);国家重点研发计划项目“中南有色金属冶炼场地综合防控及再开发安全利用技术研发与集成示范”(编号:2018YFC1802700)资助。

摘　　要：潜水蒸发计算方法通常依据潜水水位消退规律建立经验和半经验公式,或是依据土壤—植物—大气连续体建立的SPAC模型。但在设置排水沟控制潜水水位的地段,潜水水位的消退受沟渠排水与潜水蒸发的共同影响,需建立特定水文地质条件下的渗流力学算法。结合实际观测统计制度,将潜水蒸发及灌溉回归等变量离散成阶梯函数;将设置滚水坝的排水沟,概化为水位稳定不变的第一类边界,建立沟渠边界控制下含阶梯函数型源汇项的潜水非稳定渗流模型;利用Laplace变换给出模型解析解,并通过数值法验证解析解的可靠性。依据模型的解,建立利用潜水水位动态实测数据逐日计算潜水蒸发强度的递推公式,讨论沟渠边界的影响;以安徽淮北平原的一个实例,演示方法应用过程与步骤。计算农田潜水蒸发的渗流力学方法,原理上有别于基于潜水位消退规律或SPAC模型的现行算法,且新方法可清晰反映边界条件的影响,计算所需参量较少,易于实际应用。In previous studies,methods for calculating phreatic water evaporation were based on empirical and semi-empirical formulas established by the law of phreatic subsidence,or were based on the Soil-PlantAtmosphere Continuum(SPAC)model.However,in the section where the drainage ditch is set to control the phreatic water level,the decline in the phreatic water level is affected by the ditch drainage and phreatic evaporation;therefore,it is necessary to establish a seepage mechanics algorithm under specific hydrogeological conditions.Combined with an observation statistical system of observation data,phreatic water evaporation and irrigation regression were discretized into a step function.The drainage ditch with a rolling dam was generalized into the first type of boundary with a stable water level,and an unsteady seepage model of the phreatic water with a stepped function source sink term under the control of the ditch boundary was established.The analytical solution of the model was derived using Laplace transform,and the reliability of the analytical solution was verified using a numerical solution.Based on the solution of the model,a recursive formula for calculating the evaporation intensity of the phreatic water daily by using the dynamic measured data of the groundwater level was established,and the influence of the ditch boundary was discussed.Taking the Huaibei Plain in the Anhui Province as an example,the application process and steps of the method were demonstrated.The seepage mechanics method for calculating phreatic water evaporation for farmland is different from the existing algorithms based on the submergence law of the phreatic level or SPAC model in principle.The new method can clearly reflect the influence of boundary conditions and requires fewer parameters for calculation,and it is thus more convenient to apply.

关 键 词：潜水蒸发 阶梯函数 潜水非稳定渗流 LAPLACE变换 递推公式 

分 类 号：P343.8[天文地球—水文科学] S152.73[天文地球—地球物理学]