Repair, Evaluation, Maintenance, and Rehabilitation Research Program: Geotechnical Aspects of Rock Erosion in Emergency Spillway Channels. Report 3. Remediation

摘要

Remediation of unlined emergency spillway erosion damage is a relatively new, but major, concern to the US ACE districts and to other dam owners and operators. Remediation design is highly site-specific and must be cost-effective, address public safety, and to 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 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, relief of uplift pressures, and placement of geotextiles and natural grasses (especially in poorly lithified rocks and soils) may also offer useful alternatives. (EDC)