Mining

Mopani Copper Mines – Ventilation Shaft Grouting – Kitwe, Zambia, 2018-2019

Sovereign performed grouting of the Synclinorium Primary Ventilation Shaft at Kitwe, Zambia. This shaft was designed and constructed with the ventilation fans installed at the surface. There was water ingress into the shaft at various horizons in the upper 120m from surface, and the total inflow was originally estimated to be in the volume of 5000 liters per hour. The water entering the shaft had a very corrosive effect on the fan steelwork, and therefore was detrimental to the performance and the projected life span of the fans.
Sovereign designed a drilling and grouting program involving vertical holes drilled at locations outside of the shaft that intercepted the water leaks without removing of any of the fan infrastructure.
A shaft camera survey was performed to determine target drilling depths and a total water inflow water measurement was made prior to commencement of grouting. The actual water ingress into the shaft was measured at 10,130 liters per hour, more than double the 5000 liters per hour anticipated prior to the time of construction.
Upon completion of the grouting program the final water ingress measured at the bottom of the shaft was 82 liters per hour, better than a 99% reduction!
Drilling and grouting was carried out over a 90-day, incident-free period via down-stage pressure-grouting through 12 vertical diamond-drilled holes using a combination of Sovereign’s proprietary NOH2O® grout and Ordinary Portland Cement grout.

XNA Sinclair

British Coal – Whitemoor Mine. No 2 shaft. (Cementation Mining Ltd. UK JV) – UK, 1997

Over a period of several weeks, the No. 2 Shaft experienced an increased water make from 90 liters per minute to over 410 liters per minute. SCEM66 was used to successfully reduce the total inflow to less than 15 liters per minute.

Normandy Golden Grove – Scuddles Mine – Up-Cast Ventilation Shaft – WA,1992-1993

The 350-meter deep Northern Up-Cast Shaft of this mine was raise bored to 4.1 meters diameter and, at time of completion, registered 1536 liters per minute of water ingress. Apart from excessive pumping costs, this large volume in the shaft decreased fan efficiency and caused problems with water spray onto surface electrical power stations and surrounding vegetation. It was critical to eliminate airborne water in the shaft that would become entrained in the up-cast airflow.

Geological investigations suggested that water was entering the shaft in two zones (145 meter and 179 meter depths) and that it was unlikely that water inflows would be encountered at depths greater than 200 meters. SCEM66 was applied from a 2 deck stage suspended from an air winch capable of descending to a 200 meter depth. Shaft inspection revealed water ingress was from both vertical and horizontal cracks and fissures.

Water sealing by drilling and injecting was systematically carried out from the 114 meter level downward. Within one week all the airborne water was eliminated and measurement in the shaft at the 200 meter depth showed residual water make of 75 liters per minute. Additional measurements at a V-notch weir at the base of the shaft indicated water make of 335 liters per minute, indicating that leakage was occurring below the 200 meter depth.

Some six weeks later, readings at the bottom of the shaft indicated water ingress had increased to 970 liters per minute. In December 1992, Sovereign remobilized and inspected the entire shaft. The inspection revealed that the raise boring had intersected an HQ diamond drill hole at the 273 meter depth. The drill hole was discharging more than 600 liters per minute at the time of the inspection. The inspection also revealed that the water table around the shaft had recovered after the first application of SCEM66 and the water table was now at a shallower level situated above where grouting had previously occurred.

In June 1993, the top 130 meters of the shaft were lined with reinforced concrete. At that time, the diamond drill hole and other previously untreated water ingress zones were sealed with SCEM66. Total shaft water make was reduced to less than 120 liters per minute.

Gwithian Outfall Shaft, Penzance – Cornwall, England

The new Penzance/St. Ives Sewerage Scheme in Cornwall required the sinking of a 6.1-meter diameter shaft to a depth of 60 meters on the shore at Gwithian, to provide access to a 2.1 km long outfall tunnel to be driven out beneath St. Ives Bay. Initial ground support through the upper water-bearing sands, gravels and fractured killas (metamorphosed sedimentary rock marginal to igneous intrusions) was by precast concrete sections.

High water inflows were encountered while sinking through the water-bearing strata. Despite attempts to control water through backwall grouting with cement, the water make increased to over 1560 liters per minute at the base of the water-bearing interval at 35 meters depth. Due to the high inflow rate, cement grouting, even with use of bridging materials, was unsuccessful.

SCEMm66 was modified to yield the desired coagulation characteristics in the fast-flowing, saline water. After injection through the segmental lining over a 9 shift period, the water inflow was reduced from 1560 liters per minute to 114 liters per minute.

Pasminco Mining – Broken Hill South Mine (No. 5 shaft and Raise Bore Holes) – New South Wales (NSW), Australia, 1990

Broken Hill No. 5 Ventilation Shaft. During sinking of a new shaft, water entered the pilot hole at 300 liters per minute, despite a major cement grouting program from surface. Reaming of the pilot hole to 6.5 meters increased the flow to 850 liters per minute. In-shaft grouting with SCEM66 during 1990 reduced the shaft water make to 15 liters per minute.

Broken Hill Raise Bore Holes. The ingress of water into two 2.4-meter diameter raise bore holes (one each used for transport and ventilation) was reduced using SCEM66 from 60 liters per minute to less than 5 liters per minute in one shaft and from 120 liters per minute to less than 20 liters per minute in the other.

Samancor – Waterkloof Mine raise bore holes – RSA, 1990

Late in 1990, the South-East and South-West 1.83-meter diameter ventilation raise bore holes intersected water at 40 liters per minute and 60 liters per minute, respectively. The water table cone of depression was of concern, because local residences were entirely dependent on groundwater for potable water.

Over a two-week period, the mine unsuccessfully attempted to ring drill and grout by conventional methods. Sovereign mobilized, and sealed the South-West raise bore with SCEM66 in two days. Using longer holes to extend through incompetent ground, the South-East raise bore was sealed in four days under adverse conditions with heavy rain and water-logged turf.

West Driefontein Gold Mine, Vaal Reefs No 11 Shaft – Transvaal, RSA, 1990

Groundwater in dolomite was intersected from 100 meters to 600 meters depth. At 600 meters, the inflow into the shaft was 624 liters per minute. After 60 days of sealing, the inflow was reduced to 138 liters per minute, allowing normal shaft sinking operations to proceed.

A subsequent contract was awarded to apply SCEM66 to some 30 discrete areas of the tunnel where inflows varied between 1080 liters per minute to less than 1 liter per minute. These areas were all successfully treated with SCEM66 in 10 shifts.

Northam Platinum Mine – No 1 shaft – Transvaal RSA, 1989

During November 1988 the sinking crew at No. 1 Shaft reported intersecting water in a pilot hole at 4 level plat development. Attempts to pump cementitious grout via a telescopic packer proved unsuccessful. Drilling of additional pilot holes, together with the grouting program, fractured the surrounding rock so that what was only an intersection in a pilot hole subsequently became a general breakout through numerous fractures in the face and side-wall. Water inflow increased to 850 liters per minute, and water temperature was 55° C which was 2° C higher than the virgin rock temperature in the area.

In view of high hydrostatic pressure (17 MPa), the relatively weak tensile strength of the rock (14 MPa) and proximity to the face, it was decided to install a more remote seal closer to the source of the water. Numerous holes were then drilled into the fracture and grouted, but flow velocities within the water-bearing fractures were simply too high for emplacement of an effective cement grout seal.

During January 1989, Sovereign was contracted to seal the water ingress. Three strategically placed holes were drilled. Dye testing was performed to confirm adequate connection with the water-bearing fractures. SCEM66 with activator was injected, and the sealing operation was successfully completed within a single 8-hour shift.