Highway Slope Manual

77
Table 9.1 Classification of Landslide Incidents Affecting Roads
Incident
Examples
Classification
Serious
(a) An incident affecting a road with casualties or
suspected casualties. (1)
(b) An incident which has resulted in closure of a
Category A Economic Consequence facility (e.g.
an expressway, a trunk road or a primary
distributor such as North Lantau Expressway,
Tuen Mun Highway, Ching Cheung Road,
etc. (2) ).
(c) An incident which has resulted in closure of a
sole access to critical services (3) , e.g. hospitals,
fire stations, etc.
(d) An incident affecting a road which necessitates a
major evacuation of affected buildings.
Landslide Inspection
• Top priority should be assigned
for inspection.
• Road owner should mobilise a
professional civil!highway
engineer (or an equivalent level
staff) from his maintenance
team and the emergency
contractor to attend the site
inspection.
• A geotechnical engineer (GE)
should also be requested to
inspect the site immediately.
Significant
An incident which is not minor but does not fall into
the serious incident category.
• Lower priority than serious
incidents (4) .
• A GE should be requested to
inspect the site in a priority
order on the basis of
consequence and other factors
such as available resource,
traffic and weather conditions,
geographic locations, etc.
Minor
An incident with no immediate consequence, e.g. a • Lowest priority.
small-scale landslide say < 10 m 3 affecting a rural • Road owner, s maintenance
road. For roads of a higher consequence category, staff to inspect the site first and
the volume of debris should be less than 5 m 3 for the seek geotechnical advice if
incident to be classified as minor.
necessary.
Notes: (1) The Fire Services Department being called out for a rescue operation for a slope failure affecting a
road may be an indication of a serious incident.
(2) A list of such roads (e.g. Red and Pink Routes) is maintained by the Transport Department and
Highways Department.
(3) A list of such roads should be maintained by the road owners.
(4) Incidents liable to develop into serious incidents should be accorded priority for site inspection.
The factors that could have contributed to the slope failure should be carefully
assessed during the landslide inspection, where site conditions permit. Figure 9.1 shows
some of the common factors that may contribute to the failure of man-made slopes. In all
cases, the road owner's maintenance staff with the assistance from the police should take
immediate action (e.g. cordoning off the site) to safeguard the public prior to seeking the
necessary geotechnical advice.
Landslide inspection should not be confined to the boundary of a failed man-made
slope feature. Where safe access is possible, inspection should be extended to cover the
ground beyond the crest of the slope, if considered necessary, as well as the road and its
drainage provisions above or below the slope, to identify areas of distress including tension
cracks. Some distressed slopes may exhibit progressive movement but rapid failure may be
triggered by subsequent heavy rain infiltrating into the tension cracks. Therefore, any