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|Title:||Geotechnical aspects of rock erosion in emergency spillway channels. Report 3, Remediation|
|Authors:||University of Southern Mississippi. Department of Geography.|
University of Missouri--Rolla.
Repair, Evaluation, Maintenance, and Rehabilitation Research Program.
Cameron, Christopher P.
Patrick, David M.
Bartholomew, Craig O.
Hatheway, Allen W.
May, James H.
|Publisher:||Geotechnical Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: REMR research at the US Army Engineer Waterways Experiment Station has established that remediation of unlined emergency spillway erosion damage is a relatively new, but major, concern to the US Army Corps of Engineers (CE) Districts and to other dam owners and operators. The REMR work unit conducting the current investigation has identified numerous CE and other Federal, institutional, and private-sector dams that have experienced erosion damage in their unlined spillway channels. However, only a few projects have implemented or planned remedial and/or preventive measures. Remediation design is highly site-specific and must be cost-effective, address public safety, and provide continued reservoir operations. Selection of remedial technique(s) must be established by site-specific characterization of the rocks forming an unlined spillway channel in terms of rock composition(s), hardness, structural and stratigraphic discontinuities, and precursor erosion elements, all of which determine rock erodibility and its rate. Erosion probability indices based on methods which combine rock mass parameters (composition, hardness, structural discontinuity, etc.), which determine "rippability," with lithostratigraphic continuity may allow for site-prioritization in terms of the need for remedial and preventive techniques. Potentially useful remedial engineering techniques include cement-based methods such as grouting, shotcrete, soil cement/roll crete, and high-strength unreinforced and reinforced concrete, as well as rock bolts, wire mesh, gabions, and riprap. Potentially useful erosion preventive measures include construction of energy dissipators and cut-off walls and the removal of vegetation and other obstacles to flow. Flow rerouting, the relief of uplift pressures, and the placement of geotextiles and natural grasses (especially in poorly lithified rocks and soils) may also offer useful alternatives. The majority of these remedial techniques have been utilized previously in various erosion protection schemes (e.g,, stream banks, canals, levees, etc.); however, their use in unlined emergency spillway channels has not been extensive and there is little documentation available. The selection of a particular remedial technique will depend upon site conditions and costs which are highly variable for a given method. The present study established a need for more published documentation of performance and effectiveness of remedial measures as well as efforts to predict rock erosion in emergency spillway channels by the use of erosional indices.
|Appears in Collections:||Technical Report|