降雨条件下残积土的优先渗流机理分析
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摘要
为揭示强降雨条件下残积土的优先流水分运移特性,基于双重孔隙模型,采用有限差分技术编制计算程序,对考虑与不考虑大孔隙的土体模型入渗进行比较,并对降雨强度、持时、基质域与大孔隙域间的水分传导系数(Ksa)等对水分非平衡迁移特性进行分析。结果表明,相同降雨条件下,考虑大孔隙条件下土体基质域湿润峰深度约为不考虑大孔隙条件下湿润峰深度的3倍,且同一湿润峰位置处的含水率较大。随着雨强和持时的增加,水流通过大孔隙入渗导致湿润峰深度快速增加,两域水分交换深度逐渐增大,但其峰值减小。增大Ksa值,土体基质域湿润峰深度逐渐增大,而大孔隙域湿润峰深度逐渐减小。
In order to reveal characteristics of preferential water flow under heavy rainfall,based on dual porosity model,the permeabilities of soil models with and without consideration of macropore were compared,and influence of some factors on seepage mechanism of non-equilibrium flow was analyzed. The results show that the depth of wetting front(water content of matrix domain)calculated by unsaturated preferential flow model is about 3 times of that calculated by unsaturated seepage model,and that the moisture content at the same wetting front is larger. Depth of water exchange and wetting front will increase with the increase of rainfall intensity and duration time but peak of depth of water exchange will decrease. The depth of wetting front of soil matrix domainincreases gradually while the depth of wetting front of macropore domain decreases with the increase of K_(sa).
In order to reveal characteristics of preferential water flow under heavy rainfall,based on dual porosity model,the permeabilities of soil models with and without consideration of macropore were compared,and influence of some factors on seepage mechanism of non-equilibrium flow was analyzed. The results show that the depth of wetting front(water content of matrix domain)calculated by unsaturated preferential flow model is about 3 times of that calculated by unsaturated seepage model,and that the moisture content at the same wetting front is larger. Depth of water exchange and wetting front will increase with the increase of rainfall intensity and duration time but peak of depth of water exchange will decrease. The depth of wetting front of soil matrix domainincreases gradually while the depth of wetting front of macropore domain decreases with the increase of K_(sa).
引文
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[2]郑晓栩.厦门地区花岗岩残积土降雨滑坡模拟试验及土体破坏细观演变规律研究[D].厦门:厦门大学,2014.
[3]程金花,张洪江,史玉虎,等.长江三峡花岗岩地区优先流对渗流和地表径流的作用[J].水土保持通报,2007,27(2):18-23.
[4]徐宗恒,徐则民,曹军尉,等.土壤优先流研究现状与发展趋势[J].土壤,2012,44(6):905-916.
[5]吴庆华,朱国胜,崔皓东,等.降雨强度对优先流特征的影响及其数值模拟[J].农业工程学报,2014 30(20):118-127.
[6]魏虎伟,程金花,张洪江,等.四面山2种林地大孔隙特征与优先流关系研究[J].水土保持学报,2014,28(4):263-268.
[7]吴宏伟,陈守义,庞宇威.雨水入渗对非饱和土坡稳定性影响的参数研究[J].岩土力学,1999,20(1):2-15.
[8]林鸿州,于玉贞,李广信,等.降雨特性对土质边坡失稳的影响[J].岩石力学与工程学报,2009,28(1):198-204.
[9]张社荣,谭尧升,王超,等.强降雨特性对饱和—非饱和边坡失稳破坏的影响[J].岩石力学与工程学报,2014,33(S2):4102-4112.
[10]GERKE H H,GENUCHTEN M T.A dual-porosity model for simulating the preferential movement of water and solutes in structured porous media[J].Water Resources Research,1993,29(2):305-319.
[11]VOGEL T,GERKE H H,Zh ANG R,et al.Modeling flow and transport in a two-dimensional dual-permeability system with spatially variable hydraulic properties[J].Journal of Hydrology,2000,238(1):78-89.
[12]KOHNE J M,MOHANTY B P.Water flow processes in a soil column with a cylindrical macropore:Experiment and hierarchical modeling[J].Water Resources Research,2005,41(3):1-17.
[13]杨改强,霍丽娟,杨国义,等.利用MATLAB拟合van Genuchten方程参数的研究[J].土壤,2010,42(2):268-274.
[14]阙云,林登辉,陈嘉.强降雨条件下含大孔隙土柱水分非平衡运移特性[J].同济大学学报(自然科学版),2017,45(4):488-496.