DRILL AND BLAST | TECHNICAL


the pressure curve based on previous research


(Hayashi and Haimson, 1991; Raaen et al, 2001). “I believe the RSRT to a large extent can replace


more advanced stress measurement techniques when it comes to pressure tunnel design investigations, where we only need to measure the minimum principal stress,” he explains. “Interpretation can be made visually by detection of


a characteristic behaviour of the pressure development during fracture closure. No need for advanced pressure transient analysis.” Ødegaard explains that the method has been


developed with a robust, simple and semi-automated test protocol and there would be less requirement for specialised testing crews. But any testing should be planned and overseen by qualified personnel, he adds. The RSRT method is new and has had one full-


scale field trial for verification, with 29 test cycles over seven boreholes at Løkjelsvatn hydro plant, Norway. The test sites were measured by the standard methods beforehand and RSRT results correlated well. It is believed many tests down boreholes may be leading to initial rock fracturing and may not only be the controlled jacking open of existing slight cracks. More tests should be made of the system, though, he says. Companies involved with RSRT include


Injeksjonsteknikk, which developed an injection pump for routine execution of the tests, and, says Ødegaard, plans to use it for stress measurements on drill- and-blast tunnels in hydropower projects. The RSRT system he adds is to be among the stress measurement provided by Stantroll, which has established offices in The Philippines. Next steps also include supporting better grouting


operations. The idea, he tells T&T, is to look at grouting where the emphasis in recent years has been to keep pressures as high as possible while trying not to locally or unintentionally jack open the rock – enlarging or creating more minor cracks. Research would measure rock stress before each round of grouting and, it is hoped, quickly assess the maximum allowable grouting pressure to reduce the risk of hydraulic failure. “I am advocating a change from the current


approach of performing relatively few, and targeted, measurements,” he says, “over to an investigation strategy with a more distributed approach,” – and able to take measurements along the entire length of a tunnel. Using existing and not specialised or costly equipment, plus gaining more data to better refine designs, is a combination Ødegaard believes can help tunnelling performance and economics without causing impact to the drill-and-blast work at the face.


TRENDS AND EQUIPMENT Technology is advancing in drill-and-blast as well as equipment for other traditional methods of excavations. The trend is towards more instrumented and intelligent tunnelling drills, Sandvik’s product manager of tunnelling drill products Tommi Salo tells T&T. Salo says: “Customers are also asking for more multi-


purpose equipment” – such as for injection drilling, pipe umbrella drilling, and hollow bar anchors – “in addition to traditional face drilling.” Sandvik’s latest launch is the DT923i with the


improved boom design and rod handling system SRH, and which completes the i-series following the earlier launch of DT1132i. “Both drills have been used in tunnel projects in Europe and we have had good feedback,” adds Salo. “Some of the new drill rigs have also been sold to Asia.” The rigs are working on Stockholm subway, where


the rock is relatively hard and work includes a lot of injection drilling using the SRH rod-handling system, adds Salo. The DT923i has two electro-hydraulic booms with


automatic computer-controlled drilling functions. The rig also uses the recently introduced RD5 series high- frequency rock drills. An additional product for the company’s offering is


the AT umbrella pipe system, from its recently acquired subsidiary DSI Underground. Last year, Sandvik introduced the iSURE 8.1 version of


its excavation process control information management software aimed at helping to improve drill-and-blast performance. The new version enables more advanced metrics analysis and produces Key Performance Indicators (KPIs) based on data collected, round by round, onboard the i-series drill rigs. Recorded data include location of holes, recording


every 20mm using the Measure While Drilling (MWD) method, and can include geological interpretation of the rock and scanned point clouds of the tunnel profile achieved. Sandvik says the data can be studied per round or from the perspective of progress on each tunnel on a project. The iSURE 8.1’s approach with KPIs is to help dive into


analyses of production data (drilled volume and total length achieved, number of different types of drilled holes, realised blasting pull-out factor, linear advance of the tunnel, and changes in rock drillability) and realised schedule, including cycle time. Results can be compared across rigs and tunnels, and by time. Salo notes a rise in popularity for training simulators,


supporting remote training which has been important during Covid travel restrictions. Sandvik has its Digital Driller package to meet the needs, and plans to add a module matched to the DT923i rig this year. Among recent innovations from Epiroc are:


introduction of its Boomer M20 face drill rig with internal hydraulics; the COP MD20 rock drill designed to have longer service intervals; and the Avatel mechanised, semi-automated explosives charging system through its collaboration with Orica. Epiroc also notes increasing demand for automation and digitalisation, and it has lifted its stake to full ownership of underground positioning systems business Mobilaris. Among other 1business moves, Orica announced


two months ago a deal to sell its ground engineering products subsidiary, Minova, to European investment firm Aurelius Group.


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