Civil Engineering Association

Regular maintenance is essential for all man-made slopes and retaining walls, disturbed terrain features and natural terrain hazard mitigation measures to avoid deterioration or to upkeep their functions. The purpose of this Geoguide is to recommend a standard of good practice for the maintenance of man-made slopes and retaining walls, disturbed terrain features and hazard mitigation measures provided to natural terrain (e.g. boulder fences and check dams). The document is aimed at professional geotechnical engineers, although it will also be useful to the general public, many of whom carry responsibility for slope maintenance as owners of property. The general public may refer to an abridged version of the Geoguide: Layman’s Guide to Slope Maintenance (GEO, 2003a), produced by the Geotechnical Engineering Office, for simplified guidance on matters related to slope maintenance. This Geoguide deals basically with the maintenance inspections and maintenance works necessary to keep in good condition well-designed and properly constructed slopes and retaining walls and man-made mitigation measures provided to natural terrain. The maintenance inspections and works recommended herein can also reduce the probability of instability of slopes and retaining walls and disturbed terrain features which are not up to the current geotechnical standards for design and construction.
Maintenance inspections are sub-divided into four categories:
(a) Routine Maintenance Inspections, which can be carried out by any responsible person with no professional geotechnical knowledge,
(b) Engineer Inspections for Maintenance, which should be carried out by a professionally-qualified geotechnical engineer,
© Regular Checks of Buried Water-carrying Services, which should be carried out by a specialist leakage detection contractor, and
(d) Regular Monitoring of Special Measures, which should be carried out by a firm with special expertise in the particular type of monitoring service required. Such monitoring is only necessary where the long term stability of the slope or retaining wall relies on specific measures which are liable to become less effective with the passage of time. Chapter 2 describes the recommended approach to maintenance management and provides guidance on the necessary action to be taken for slopes and retaining walls, disturbed terrain features and natural terrain hazard mitigation measures. In addition, the importanceof a Maintenance Manual and maintenance records is highlighted. Chapter 3 provides guidance on the scope of maintenance requirements for man-made slopes and retaining walls, including the purpose and scope of Routine Maintenance Inspections and Engineer Inspections for Maintenance. It describes the requirements for the frequency and personnel for these inspections. In addition, the need to undertake Regular Checks of Buried Water-carrying Services is presented. It also outlines the need for, and the types of, Regular Monitoring of Special Measures. Chapter 4 describes technical aspects of maintenance inspections pertinent to the well keeping of man-made slopes and retaining walls, and Chapter 5 prescribes the use of preventive maintenance works to improve man-made slopes and retaining walls. Chapter 6 gives guidelines on the maintenance of disturbed terrain features. Chapter 7 provides guidance on the maintenance of hazard mitigation measures that are provided to natural terrain. The mitigation measures include stabilisation measures to prevent failure and defence measures to protect developments from landslide debris originating from natural terrain. It is important to remember that maintenance inspections and works as specified in this Geoguide will only serve to maintain the existing level of stability (i.e. existing margin of safety against failure), or to bring about marginal improvement. That is to say, slope maintenance alone may not be adequate in ensuring that a slope or retaining wall meets the geotechnical standards as stipulated in the Geotechnical Manual for Slopes (GCO, 1984). To determine whether the slope or retaining wall meets the required standard, the owner or the party required to maintain the land may have to arrange for a Stability Assessment to be carried out by a professionally-qualified geotechnical engineer. Upgrading works will be required in case the slope or retaining wall does not satisfy the current safety standards.