|Fausey, Norman - Norm|
Submitted to: Ohio Academy of Science Meeting
Publication Type: Proceedings
Publication Acceptance Date: 4/8/1998
Publication Date: N/A
Technical Abstract: Where grain-size analyses are available, fractures in glacial till have been identified in settings ranging from over 45 percent to 18 percent clay-sized materials. X-ray defraction of these clays reveal that, for the most part, they are illite and kaolinite. Montmorillinitic clays are not commonly found in Ohio and, where present, are typically found in shallow soil horizons, not in the less weathered underlying glacial materials. Illitic clays are the major Ohio clays and occur in all horizons. Illite, once dehydrated, does not rehydrate, so fractures controlled by illitic clays remain open, even if the site is resaturated at a later date. Investigations to date have revealed that settings with levels as low as 10 percent total illite will maintain a fracture system once it has been formed. Ohio scientists are beginning to build a database of known fracture locations and conditions so that it may be possible to predict where fractures may be expected. While the exact location of the boundary where secondary fracture flow dominates is still not clearly defined, a range of easily definable conditions where secondary porosity/fracture flow should be anticipated, planned for and investigated in any site assessment, have been established. Any site where materials have at least 10 percent total illitic clays, should be investigated for fractures. Further research may lower that threshold.