SHAFT SINKING
removing or separating the worker from the hazard .
Eric Kohtakangas , Senior Executive Vice President of the company , told IM : “ The obvious challenge is the current rock cutting technology available for hard-rock conditions .”
While the industry has come a long way to make shaft sinking systems safer than they were , say , 30 years ago , the result is a process that is very technical in nature with many engineered solutions to mitigate risk and prevent incidents during shaft sinking .
This has led to the drop in advance rates that many in the industry have observed in recent decades , with schedules pushed back in favour ( rightly ) of safety .
“ The challenge we face in the shaft sinking business is the ability to maintain the historical shaft sinking advances from the past with the advent of new technology into the shaft sinking process ,” Kohtakangas said , adding that large
diameter shaft boring with raise bore in hard rock still offers near to or better than traditional drill and blast advance rates .
Within this , he singled out mechanised bolting specifically , saying that this process is far slower than traditional methods – again , a reflection of the complex nature of sinking .
“ The sinking systems are very technical and
complex today ; ground support requirements are far greater than they were 30 years ago , and many shafts are getting deeper ,” Kohtakangas said . “ Every sinking setup and shaft design is different as no two sinks are the same so there are many factors that influence the sinking rates .”
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Still , the more shafts sunk using mechanised methods , the more data there is to examine if boring technologies can be applied to certain projects .
“ I think if the rock type is suitable for the current mechanised technologies , then more clients are willing to accept the risk that may affect the overall schedule ,” he said . “ Today there is more benchmarking data on recent shafts excavated using mechanised technology , which gives mine owners more confidence in the risks associated with schedule when choosing the sinking method .”
And , in raiseboring , Cementation Canada has much of this data , with a recent milestone being the completion of the full faced raisebored raise at Solvay Chemicals # 5 shaft in Green River , Wyoming , USA : a project that required the company to sink a 22 ft ( 6.7 m ) diameter shaft , complete with concrete liner , from surface to a depth of 1,506 ft ( 459 m ).
Kohtakangas believes projects like this show Cementation Canada has truly made a difference to the shaft sinking market over the last 25 years . “ We believe we can sink shafts today without harm ,” he said .
“ Obviously safety is our first priority , and making sure we get the right estimate and schedule for any shaft sinking project we undertake . Once in execution , Cementation is committed to continuous improvement on every project we undertake to ensure performance is in line with the planned and scheduled performance .”
In practicality , this has led to the establishment of a performance management system that , Kohtakangas says , continuously drives ideas and actions for improvements .
This leverages two components to drive performance – a short interval control system using a software called Groundhog and a daily performance management ( improvement ) system that promotes continuous communication around variances in actual shift progress versus plan ( mentioned in detail in last year ’ s shaft sinking feature ).
The combined system cascades priorities and targets , creates transparency and drives controllable variance actions , according to Kohtakangas , who mentioned it had been used successfully at the Onaping Depth sinking project in Ontario , Canada .
Cementation Canada is currently excavating the last shaft station ( 2605 Level ) at the bottom of the Onaping Depth shaft , with plans to return to the shaft bottom loading pocket and then facilitate a changeover to the production team . The company commenced full-face blind sinking at the project in October 2021 , with the crews reaching the first of three shaft stations around the 2,490-m-depth level in July 2022 . The
28 International Mining | SEPTEMBER 2023