Characteristics of Infiltration Recharge at Thickening Vadose Zone Using Soil Hydraulic Parameters
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摘要: 为探讨包气带深部增厚区土壤水力参数变化对入渗补给过程的影响,采用压力膜仪对河北正定深部包气带(8.0~21.0 m)10个原状土样进行水分特征曲线测试,利用RETC软件中Mualem-van Genuchten导水率模型对其拟合,获取含水率与非饱和导水率的关系曲线,并根据达西法对其进行分析讨论.结果表明:场地包气带深埋区的非饱和导水率为25~240 mm/a.当某一埋深历史水位下降速度越快,该埋深处相同含水率情况下土壤非饱和导水率越大,说明对应土层的入渗补给强度越大;因包气带厚度增大使原来位于饱水带的层状非均质土层转变为包气带,潜水位波动下降过程中深部包气带土层因排水压密作用,使得土壤水力特性发生变化,进而影响垂向入渗补给过程.Abstract: Ten undisturbed soil samples were collected from deep vadose zone (8.0-21.0 m) at Zhengding, Hebei, and analyzed to study how thickening vadose zone impacts the infiltration recharge processes. These samples were measured by Pressure Plate Extractor to gain the soil retention curves, which were fitted by Mualem-van Genuchten Model using RETC software. Unsaturated hydraulic conductivity and the relation curves were obtained through the curve-fitting processes. The impact on the infiltration recharge processes at the thickening vadose zone is discussed according the Darcy's equation. It is concluded that the unsaturated hydraulic conductivities at sampling time were 25-240 mm/a at the depth of 8.0-21.0 m. If the velocity of water table decline was fast at a certain depth historically, the unsaturated conductivities with same water content should also have large values, which shows the soil has large infiltration capacity. Soil hydraulic parameters and infiltration capacities would change because of water table fluctuated-declining and drainage consolidation, which would impact vertical infiltration recharge.
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Key words:
- deep vadose zone /
- soil water characteristic curve /
- recharge intensity /
- RETC /
- Darcy's equation /
- soil conditions /
- groundwater
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图 1 包气带厚度足够大时土壤基质势随深度分布曲线(Nimmo et al., 1994)
a.均质剖面;b.层状剖面
Fig. 1. Hypothetical profile of matric pressure as a function of depth in an unsaturated zone deep enough that its lower portion has a constant downward flux of water in profiles
图 5 石家庄水位下降曲线(张光辉等,2008)
Fig. 5. Downwards water curves at Shijiazhuang
表 1 原状土样采集深度及颗粒分析数据
Table 1. The sampling depth and soil texture of undisturbed soil samples
编号 采样深度(m) 颗粒组成(%) 干密度(g/cm3) 国际制定名 粘粒 粉粒 砂粒 1号 8.0~8.5 7.30 26.08 66.64 1.66 砂壤土 2号 9.4~9.5 17.92 60.74 21.29 1.58 粉砂质粘壤土 4号 10.4~10.6 20.14 59.68 20.19 1.63 粉砂质粘壤土 5号 11.0~11.2 8.88 30.15 60.95 1.86 砂壤土 6号 11.6~11.7 10.23 39.83 49.96 1.78 壤土 7号 12.0~12.1 10.17 45.71 44.10 1.68 粉砂壤土 11号 18.5~18.6 12.44 48.97 38.55 - 粉砂壤土 12号 18.7~18.9 5.78 20.16 74.04 1.58 砂壤土 13号 19.8~20.0 11.61 37.46 50.95 1.85 壤土 14号 20.6~20.8 6.78 32.41 60.77 1.71 砂壤土 注:土壤质地分类由中国地质大学生物地质与环境地质国家重点实验室激光粒度仪测定. 表 2 土壤水分曲线测试压力值设置
Table 2. Pressure setting values of soil water retention curve
压强值(105 Pa) 水柱高度(cm) 0.02 20.41 0.05 51.02 0.10 102.04 0.20 204.08 0.32 326.53 0.54 551.02 0.84 857.14 1.20 1 224.49 1.66 169.88 2.24 2 258.71 2.94 3 000.00 表 3 土壤水分特征参数预测和拟合结果
Table 3. The prediction and fitting results of soil moisture characteristic parameters
编号 Rosetta预测 RETC拟合 θr θs α n θr θs α n R2 1 0.037 8 0.379 1 0.033 5 1.463 3 0 0.438 0 0.006 0 1.560 5 0.978 9 2 0.063 2 0.396 3 0.005 5 1.647 0 0.210 6 0.438 1 0.002 3 1.882 1 0.998 1 4 0.069 1 0.421 2 0.005 3 1.656 1 0.335 2 0.479 8 0.001 4 3.221 1 0.993 8 5 0.035 4 0.337 7 0.036 1 1.364 3 0 0.487 1 0.003 9 1.940 2 0.999 3 6 0.037 0 0.335 8 0.021 0 1.390 4 0.124 0 0.489 1 0.002 6 1.986 4 0.997 9 7 0.042 8 0.372 1 0.009 9 1.532 4 0 0.447 3 0.002 2 2.576 2 0.995 5 11 0.044 0 0.345 7 0.010 5 1.494 2 0.285 7 0.473 2 0.003 5 2.493 0 0.999 3 12 0.039 0 0.391 5 0.039 5 1.573 1 0 0.449 9 0.003 9 1.362 0 0.988 0 14 0.038 8 0.337 6 0.022 1 1.376 7 0 0.468 3 0.002 5 1.546 3 0.981 1 表 4 野外实地非饱和导水率及入渗补给速率
Table 4. Unsaturated hydraulic conductivity and recharge rate at the field
编号 取样深度(m) 岩性定名 深度区间(m) 原位体积含水率 拟合Ku值 国际制 (cm/d) (mm/a) 1 8.3~8.5 砂壤土 8.3~9.4 0.284 1 0.007 811 28.51 2 9.4~9.5 粉砂质粘壤土 9.4~11.0 0.364 9 0.030 786 112.37 5 11.0~11.2 砂壤土 11.0~11.6 0.287 1 0.016 712 61.00 6 11.6~11.7 壤土 11.6~12.0 0.328 9 0.014 499 52.92 7 12.0~12.1 粉砂壤土 12.0~13.7 0.293 6 0.065 834 240.29 11 18.5~18.6 粉砂壤土 13.7~19.5 - - - 12 18.7~18.9 砂壤土 - 0.358 1 0.011 119 40.58 14 20.6~20.8 砂壤土 19.5~21.6 0.301 6 0.006 891 25.15 -
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