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A Surface Resistivity Method for Measuring Hydrologic Characteristics of Jointed Formations.
MISSING :45 pages
A Bureau of Mines surface resistivity method has been used to determine the joint strike and coefficient of anistropy of jointed, near-surface formations at five study areas. The field studies demonstrate the use of rotated, or azimuthal, wenner-lee arrays for determining the strike of predominant joint sets. The results of the field studies include the following: in a formation having a predominant, vertical joint set, the maximum value of the apparent resistivity (pa) occurs in the same direction (azimuth) as the joint strike; the polar coordinate graph of pa for such a formation is approximately elliptical; the coefficient of anisotropy (x) can be calculated from the field data, and values of x for jointed formations are in the same range of values reported for layered formations; values of X are higher at mined sites than at unmined sites. The azimuthal resistivity method and horizontal profiling were used at a site in Pennsylvania to delineate a zone of intensely jointed and fractured bedrock that provided a flow path from a surface stream to a mine. Analysis of the data has been based on a simple model of a jointed formation having a single joint set; the success achieved to date indicates the need for a more complex model and additional field data.
IH; Report of Investigations
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division