Abstract
A comprehensive geotechnical drilling program is necessary to ensure a sufficient degree of confidence in constructing a structural model. This paper investigates the influence of the borehole inclination on the characterisation of the joint orientation. Discrete Fracture Networks (DFNs) are used to model joint set populations. The average joint properties are obtained by simulating boreholes in the DFN for three scenarios: vertical holes vs. inclined holes, increasing proportion of inclined holes and variable borehole inclinations. The results show that the estimated average dip direction is not significantly influenced by the borehole inclination, but the average dip value is closer to the population mean value for inclined holes. The percentage of joints intercepted increases when more than 70% of the boreholes are inclined. A higher percentage of joints is intercepted, and a better estimate of the average joint set dip is obtained when using boreholes at an inclination between 58 and 63 degrees.
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