| Abstract |
Hydraulic fracturing, a method of increasing fluid flow within the subsurface, should improve the effectiveness of several remedial techniques, including pump and treat, vapor extraction, bio-remediation, and soil-flushing. The technique is widely used to increase the yields of oil wells, but is untested under conditions typical of contaminated sites. The project consisted of laboratory experiments, where hydraulic fractures were created in a triaxial pressure cell, and two field tests, where fractures were created at shallow depths in soil. The lab tests showed that hydraulic fractures are readily created in clayey silt, even when it is saturated and loosely-consolidated. Many of the lab observations can be explained using parameters and analyses based on linear elastic fracture mechanics. Following the field tests, the vicinity of the boreholes was excavated to reveal details of the hydraulic fractures. Maximum lengths of the fractures, as measured from the borehold to the leading edge, averaged 4.0 m, and the average area was 19 sq m. Maximum thickness of sand ranged from 2 to 20 mm, averaging 11 mm. As many as four fractures were created from a single borehold, stacked one over the other at vertical spacing of 15 to 30 cm. |
