ABSTRACTThe point dilution test is a single-well technique for estimating horizontal flow velocity in the aquifer surrounding a well. The test is conducted by introducing a tracer into a well section and monitoring its decreasing concentration over time. When using a salt tracer, the method is easy and inexpensive. Traditionally, the horizontal Darcy velocity is calculated as a function of the rate of dilution and is based on the simple assumption that the decreasing tracer concentration is proportional both to the apparent velocity into the test section and to the Darcy velocity in the aquifer. In this article, an alternative approach to analyse the results of point dilution tests is proposed and verified using data acquired at a test site in the middle Venetian plain, northeast Italy. In this approach, the one-dimensional equilibrium advection–dispersion equation is inverted using the CXTFIT model to estimate the apparent velocity inside the test section. Analysis of the field data obtained by the two approaches shows good agreement between the methods and suggests that it is possible to use the equilibrium advection–dispersion equation to estimate apparent velocity over a wide range of velocities.
Editor D. Koutsoyiannis; Associate editor K. Heal 相似文献
Abstract The design and construction of a special-purpose laboratory catchment and rainfall simulator is described. The equipment consists of a soil catchment area that can be inclined at various angles. Additional instrumentation then measures the flow of water across the surface of, and through, the soil bed. Precipitation is provided by a unit that simulates rainfall at particular rates with uniform distribution. The equipment was used to examine infiltration, runoff and other hydrological properties of a number of soils under different rainfall intensities and with different catchment slopes. Correlations were obtained for these variables. 相似文献
磁异常反演是获取地下场源磁化率分布的重要手段之一,在地球勘探中扮演着重要角色.在磁异常反演中,对比光滑反演,稀疏反演的结果具有边界分明,物性参数分布集中的特点,更符合实际情况.针对稀疏反演,本文首先构建了具有代表性的基于L1范数目标函数,利用交替方向乘子算法可分离凸函数的特点,将极小化L1范数的优化问题分解为一系列的子问题,通过对子问题求解获得原问题的解;为了增强交替方向乘子算法的适应性,本文结合广义软阈值函数将交替方向乘子法推广于Lp(0 < p < 1)范数的反演中.为了验证本文提出的算法的有效性,采用了三种常规模型进行模拟实验.与基于L2范数的反演算法进行实验对比,结果表明,本文算法得到了边界清晰,磁化率分布更集中的反演结果.最后,将基于交替方向乘子算法的L1和Lp(0 < p < 1)范数的反演应用到青海省尕林格铁矿保护区获得的实际磁异常数据中,获得了较为符合实际地质情况的稀疏反演结果.