A gold mining company had pre-grouted around the collar for a new ventilation raise, constructed a concrete foundation and setup a raise boring machine. It was subsequently determined that un-grouted water-bearing fractures within 30 m from surface prevented deeper drilling of the pilot hole.
Company personnel contacted Peter White to arrange a site visit and provide engineering recommendations to resolve the situation by building a grout curtain so that pilot hole drilling could resume.
After assessing the site conditions and requirements, Peter developed designs and specifications for additional drilling and cement grouting work.
After the drilling and grouting contractor had mobilized to site, Peter returned to supervise cement grouting operations. Work proceeded by systematically drilling widely spaced primary holes utilizing top-hammer percussion drilling equipment and grouting using high-speed colloidal grout mixers.
Drilling and grouting work continued with secondary and tertiary holes to gradually close spacing between adjacent holes until the rock surrounding the ventilation raise had been successfully consolidated and pilot hole drilling could resume.