Highway Slope Manual

81
obtained from the inspection together with the as-built records certified by the supervising
personnel should be used to update the Maintenance Manual and to establish the need and the
priority of the slope for further upgrading or preventive maintenance works (see Section 8.).
9.2. Reopening o Roads
In making a decision to re-open a road which has been closed due to landslides, public
safety is the prime consideration and this should not be compromised for public convenience.
The necessary urgent repair works that will allow the re-opening of a road should be checked
for satisfactory completion by the professional engineer who is responsible for the works
before the re-opening of the road. For serious landslide incidents, the advice of a
geotechnical engineer should be sought on road re-opening. For all other cases, geotechnical
advice should be sought if it is necessary to interpret geotechnical data before reaching a
decision. Sufficient lead time should be allowed for any necessary inspection, monitoring
survey and consultation to be made before re-opening the road, and for arrangements to be
made to inform the public. This is especially important when re-opening of the road before
the morning rush-hours is intended.
In some instances, there may be a need to re-open a road in the shortest possible time,
e.g. for a sole access to a critical facility or for a busy road with grossly inadequate alternative
routes. Prolonged road closure could lead to unacceptable consequences to the traffic and
major disruption to the community. Where the repair works would take a long time to
complete, partial closure of the road together with implementation of suitable risk mitigation
measures may be considered. However, this should be adopted only when the risk of further
slope failure can be judged to have been reduced to an acceptable level. A road may be reopened
under certain restrictive conditions (e.g. checking of a pre-determined rainfall
intensity level not being exceeded or forecast not to be exceeded, surveillance to confirm no
further development of heavy rainfall and deterioration of the observed signs of distress, and
monitoring to confirm no trend of accelerating ground movements). In such cases, alert
levels should be established and contingency plans, which should include follow-up risk
mitigation actions by designated authorised personnel and the channels of communication,
should be agreed by all the parties concerned and clearly documented.
Conditional re-opening of a road is not recommended as a general measure as there
will be difficulties in implementing the measures effectively, in particular in forecasting the
weather condition. Also, frequent closures and re-openings of a road can cause confusion to
road users. Where a decision is made to have partial closure or conditional re-opening of a
road, good communication between all parties concerned should be maintained in order that
any difficulties that may arise can be resolved promptly.