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Feasibility of Hydraulic Fracturing of Soils to Improve Remedial Actions
Citation:
Murdoch, L. C., G. Losonsky, P. Cluxtpn, AND B. Patterson. Feasibility of Hydraulic Fracturing of Soils to Improve Remedial Actions. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S2-91/012, 1991.
Impact/Purpose:
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Description:
Hydraulic fracturing, a technique commonly used to increase the yields of oil wells, could improve the effectiveness of several methods of in situ remediation. This project consisted of laboratory and field tests in which hydraulic fractures were created in soil. Laboratory tests conducted using a triaxial pressure cell showed that hydraulic fractures were readily created in clayey silt, even when it was saturated. Laboratory observations are explained using the parameters and analyses of linear elastic fracture mechanics. Field tests were conducted during the summers of 1988 and 1989. During the1988 test, hydraulic fractures were successfully created from cement casing at depths of 2 to 4 m. The tests were limited to one fracture per borehole, and shortcomings resulted from the use of oil well equipment too large for our purposes. During the 1989 test, injection grouting equipment was used with a new method of*casing to create as many as four horizontally layered fractures from the same borehole. Following the tests, the vicinity of the boreholes was excavated to reveal details of the hydraulic fractures. In general, they were slightly elongate in plan view, and they were highly asymmetric with respect to their parent borehole; In each case, there was a preferred direction of propagation. Maximum lengths of fractures in 1989 average 4.0 m, and the average areas was 19 m2. Maximum thickness of sand in individual fractures ranged from 2 to 20 mm, averaging 11 mm. Results indicate that it should be feasible to monitor the growth of hydraulic fractures at shallow depths using injection pressure, surface uplift and surface tilt.