Stream Bank Remediation; Not Just a Geotechnical Problem

摘要

Slope failures along stream banks are caused by a combination of unfavorable conditions. Geotechnical engineers often focus on soils and groundwater issues and develop remedial schemes that are derived from a two dimensional stability analysis without giving due consideration to geologic conditions. Remedial solutions that do not account for stream dynamics may not have the anticipated life cycle and may exacerbate erosion upstream and downstream of the site under repair. Remedial solutions that consider the stream dynamics improve the slope stability and can be applied in an ecologically friendly manner. This paper presents two case histories that illustrate the geotechnical and geomorphic causes of slope failures along streams. For one case history, geotechnical issues, such as weak soils, steep slopes, high groundwater levels, and poor drainage, are the predominant causes of the slope instability. For the second case history, stream dynamics, particularly erosion of the slope's toe, caused the slopes to fail. The case histories illustrate how remedial methods are developed to address both the geotechnical and geomorphic issues. This includes traditional methods to improve geotechnical conditions and some non-traditional methods such as using the dry-mix method to improve the strength of soft sensitive clay soil. Remedial methods to address the stream conditions include measures such as river training, bank armoring, and revegetation.