Highway Slope Manual

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7.3.2 Safety Precautions
The main safety precautions that should be considered when rock excavation is to be
carried out above and adjacent to a road are given in Table 7.2. Some of these precautions
cannot be specified fully in advance in the contract documents because they are related to the
working method to be used. The precautions are most effective when addressed at all stages
of a project, as shown in Figure 7.2.
Table 7.2 Range of Safety Precautions for Rock Excavation Adiacent to Roads
(a) Drovision of method statements detailing the proposed ways and means for excavating rock adjacent to the
carriageway (which should be reviewed carefully by experienced engineers).
(b) Drovision of road closure or traffic diversion arrangements during critical slope formation operations, e.g.
• mobilisation and demobilisation of construction plant and equipment on the slope,
• rock breaking and blasting,
• rock blocks and debris removal, and
• checking for suspected misfires of blasting.
(c) Drovision of temporary rockfall containment and retention measures as appropriate, e.g. rock traps, berms,
barriers, catch fences, free hanging mesh, etc.
(d) Stabilisation of potentially unstable boulders and rock exposures prior to access road formation or
excavation, where necessary.
(e) Drovision of no 叫 blast zones close to carriageway and checking of blast hole locations and charge weights.
(f) Engaging persons who possess a valid Mine Blasting Certificate or are duly authorised by the Commissioner
of Mines in accordance with the Mines (Safety) Regulations (Government of Hong Kong, 1986) to carry out
blasting.
(g) Supervision of works by a geotechnical engineer and other suitably experienced personnel with clearly
defined and stated responsibilities and authority to suspend all works.
(h) Carrying out inspection of excavated faces by a geotechnical engineer before making arrangements for re 叫
opening the road.
(i) Independent checking of work procedures, geotechnical assumptions, adequacy of new geotechnical works
and hazard mitigation measures and stability of existing slopes, including site checks by a geotechnical
engineer and other suitably experienced personnel.
(j) Drovision of induction/awareness programme on potential rockfall hazards and training in safety aspects of
working adjacent to carriageway for site personnel who require them.
7.3.3 Rockfall Protection and Prevention
Given the uncertainties inherent in any excavation, it is unrealistic to assume that all
potentially unstable rock blocks on slopes can be identified by inspection and stabilised using
preventive methods alone (such as slope treatment which involves removal or in-situ
stabilisation of potentially unstable blocks of rock). Therefore, protective methods (such as
provision of rockfall protective barriers) should also be considered for controlling rockfalls.