Highway Slope Manual

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stabilisation/protective measures. Ground investigation works, if considered necessary,
should be carried out. Any special requirements (e.g. landscape/aesthetics, maintenance,
land-take and traffic), if dictated by the overall design geometry and constraints, should be
identified and specified in the GA, so that they can be adequately addressed in an integrated
manner at or before the subsequent design and construction stages. The likely excavation
methods and procedures that can satisfy all requirements should be identified, and any
significant construction management issues should be highlighted.
Traffic disruption may affect critical facilities which are of social or economic
importance, e.g. hospital, fire station, airport, power station, container port and the nearby
major roads. Serious traffic disruption could result in significant socio-economic loss to the
community. Where road closure is necessary for construction of the geotechnical works or
hazard mitigation measures, it may be necessary to carry out a traffic impact assessment at the
GA stage for the construction scenarios anticipated. In situations where loss of essential
services and/or social disruption are judged to be unacceptable, provision should be made in
the works contract for traffic impact mitigation measures to be implemented during
construction. This could include minimising closure to not more than a few sections of the
road at the same time, limiting the closure length, period of closure, as well as distance
between closures, or providing alternative access to the facilities during periods of road
closures. Good co-ordination of construction activities to minimise idling time could also
reduce the road closure period. The requirements of the relevant authorities should be
identified (Highways Department, 1995).
The GA should address the contractual and construction management issues related to
the geotechnical works and hazard mitigation measures. The possible impact of contract
strategy on the quality of the geotechnical works and hazard mitigation measures should be
considered at the early stage of the project. Where a Design Build form of contract is
intended to be used for a highway project with a significant proportion of geotechnical works,
in particular where the payment is to be on a lump sum basis, adequate site investigation
should be carried out to ensure that there is sufficient information to define beyond any
reasonable doubt the scope of the geotechnical works and hazard mitigation measures under
the contract. The contract should specify requirements for construction supervision and
design review, geotechnical checking, auditing and control testing to ensure quality of the
works and construction site safety (see Section 7.2). The use of Design and Build form of
contract would not be appropriate if the scope of the geotechnical works and hazard
mitigation measures could not be clearly defined for whatever reasons prior to the award of
the contract. Reference should be made to Works Bureau Technical Circular No. 31/99
(Works Bureau, 1999a) for guidance.