Tracer Tests in the Fractured Rock for Investigating Groundwater Flow Pathway
Date Issued
2014
Date
2014
Author(s)
Chan, Wan-Chen
Abstract
Groundwater flow in the fractured rock is mainly controlled by a few permeable fracture. Core analysis and acoustic televiewer can be used to examine the fracture density and orientation, but difficult to characterize whether rock fractures are permeable. In this study, we integrate a variety of field tests, including tracer test, hydraulic test, and heat-pulse flowmeter test, to locate the permeable fractures and to detect the hydraulic connections between boreholes.
The field study was conducted at Heshe hydrogeological experimental well station in central Taiwan. There are eight test wells and two observation wells at the site where the in-situ rock below the overburden is primarily shale and siltstone. Surface geological survey shows three sets of joint planes. In order to detect the preferential pathway of groundwater flow, heat-pulse flowmeter measurement was adopted to identify the depth of permeable fractures in the boreholes. It was followed by the multi-well pumping test for investigating the hydraulic connectivity between these wells. The tracer tests were then used to detect the hydraulic connectivity of permeable fractures between two wells. By injecting saltwater or nano zero-valent iron into one well, it is possible to detect the variation of tracer in the nearby wells. We found nano zero-valent iron adsorbed by a magnet array in the detection well in two tracer tests. The adsorbed nano iron can specifically locate the position of permeable fractures connecting to the injection well. Our study results show that the nano iron tracer test is a potential useful tool to investigate the preferential groundwater flow in the fractured rock.
Subjects
裂隙岩層
地下水
示蹤劑試驗
奈米鐵
Type
thesis
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