Repair, Evaluation, Maintenance, and Rehabilitation Research Program. Geotechnical Aspects of Rock Erosion in Emergency Spillway Channels. Report 4. Geologic and Hydrodynamic Controls on the Mechanics of Knickpoint Migration
Abstract
During the last decade, occurrences of emergency spillway discharges at Soil Conservation Service, Corps of Engineers, and private reservoirs have increased and, in certain circumstances, resulted in erosional damages to the spillways. Rapid headward erosion in unlined emergency spillways at Corps of Engineers reservoirs including Grapevine, Saylorville, and Black Butte caused the Corps to take a serious look at the available methods used to predict erosion damage in unlined emergency spillways. The catastrophic loss of private and Soil Conservation Service reservoirs because of knickpoint migration in emergency spillway channels was additional evidence that the mechanics of knickpoint erosion were not clearly understood. Severe erosion was documented at several Corps spillways where the flow was less than one-tenth of the designed capacity. The purpose of this research was to study knickpoint erosion phenomena with respect to the combined effects of the geologic and hydrodynamic controls. In order to study the mechanisms working at the knickpoint, several obstacles had to be overcome. First a material had to be developed which would erode like rock but would keep the eroding water clear so that the failure mechanisms could be observed. Sodium silicate and gelatin-cemented gravel in combination with Plexiglass were used to simulate knickpoints in layered rock. Next, a hydraulic flume had to be modified to accommodate layered samples.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1989
- Accession Number
- ADA216749
Entities
People
- James H. May