Active Site Supervision to Enhance Drilling & Blasting
In Hong Kong, the steep hilly terrain is a significant constraint on surface development but provides good opportunities for underground rock caverns. The systematic use of rock caverns will be the long-termed options to increase the land supply, and drill-and-blast is still the most commonly adopted excavation method in underground. However, the technology adopted in site supervision of drill-and-blast excavation has no significant advancement along the time-tunnel of development in Hong Kong. The checking on the as-built blast holes is not comprehensive enough as only the layout on the blast face and the depth of only reachable blast holes can be checked. The alignment of blast holes behind the blast face is unknown, which is however important. In addition, no qualitative and quantitative review on the geological condition ahead of the blast face can be carried out continuously while drilling.
“The relocation of Sha Tin Sewage Treatment Works to Caverns” is a pioneering project for the cavern development in Hong Kong. It showcases the use of rock cavern to unlock the precious land resources in congested urban area. The project team endeavours in adopting Measure-While-Drilling technique to uplift the current practice of site supervision. Sensors and routers are installed at the drilling jumbos to collect valuable drilling data, including the as-built alignment in three dimensions for 100% blast holes, such that live-monitoring of drilling operations could be carried out anytime and anywhere such as in office as well as on site. In case of any as-built blast holes were found to be significantly deviated from the original alignment, review on the drilling operation and rectification could be carried out immediately. Geo-mechanical data is also live-collected for rock mass analysis while drilling of each blast hole, serving like ground investigation drillholes to reveal the geological condition ahead blast face in a fast and an efficient way. The geological condition is one of the major factors in controlling the overbreak in drill-and-blast excavation as well as the blasting factors. The blast design can be reviewed and can be optimized to cope with the changing geological conditions. The huge volume of data generated will be stored into a Big Data database, which is versioned to share all the data obtained with the local construction industry. In long term, the use of Big Data would be the way in predicting the potential risks and its root cause instead of being traditionally merely responsive to an already happened event.
The site supervision for underground construction under public works projects has become more active than ever before, for which the client departments and Resident Site Supervisors (RSS) actively master the use of live data as to enhancing the safety and quality of drill-and-blast operation. The full adoption of Measure-While-Drilling are leading the site supervision sector towards a more productive, more effectively managed digital age where real time data and reporting will be available for key elements of future tunnel and cavern projects.
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