Tag Archives: Shaft boring roadheader

Anglo American ends DMC Mining shaft sinking contract at Woodsmith project

Anglo American has confirmed its Crop Nutrients business has ended the contract of its shaft sinking contractor, DMC Mining Services UK Ltd, at the Woodsmith polyhalite project in the UK.

Anglo, which only took ownership of the asset earlier this year, said DMC staff were expected to transfer to Anglo American under the Transfer of Undertakings (Protection of Employment) Regulations, and construction progress was due to continue.

DMC was awarded the design and build contract for the construction of the deep shafts at the Woodsmith project back in February 2018 when the project was owned by Sirius Minerals.

This contract would have seen it engineer and construct four shafts at the project in North Yorkshire. Those shafts include a production and service shaft, each around 1,500 m deep, and two smaller shafts associated with the materials transport system, each approximately 350 m deep. It was to sink the deep shafts using Herrenknecht’s Shaft Boring Roadheader technology.

Herrenknecht developed the SBR for the mechanised sinking of blind shafts in soft to medium-hard rock. Based on the technology of the Herrenknecht Vertical Shaft Sinking Machine, the SBR offers improved safety performance compared with conventional shaft sinking methods while also achieving higher advance rates, according to the company.

DMC, itself, had become familiar with the technology after helping successfully sink two blind shafts to depths of -975 and -1,005 m, respectively, at the BHP-owned Jansen potash project in Saskatchewan, Canada.

Sinking activities with the SBRs at Woodsmith, meanwhile, were expected to start next year, with the machines having already arrived on site.

A spokesman for the Woodsmith project said of the DMC contract cancellation: “This new structure provides us with simpler internal processes and allows us to better manage the important transition between the sinking phase and ramp-up to steady state operations.

“It also gives us greater control over processes like local recruitment and training.”

Herrenknecht heralds ‘game changer for shaft sinking in soft and medium-hard rock’

Having successfully excavated two 8-11 m diameter blind shafts using Shaft Boring Roadheaders (SBRs) at the BHP-owned Jansen potash project, Herrenknecht is leveraging all the lessons it learnt in Saskatchewan, Canada, to ensure this technology proves to be a “game changer” for the sinking of shafts in soft and medium-hard rock.

Mining contractor DMC Mining Services used two SBRs to excavate the blind shafts at Jansen, with the successful project completion acting as proof of the feasibility and advantages of the Herrenknecht SBR concept for the mining industry, according to the Germany-based company.

In August 2018, the mining industry milestone was achieved with the successful completion of two blind shafts to depths of -975 and -1,005 m, respectively, at the Jansen potash project. For the first time, shafts in the mining business were sunk using only mechanical excavation for this reference project.

Two Herrenknecht SBRs excavated the ground by a partial-face cutting method, using a cutting drum mounted on a telescopic boom. The excavated rock was then conveyed from the bench by an innovative pneumatic mucking system (PNM) and transferred into muck buckets to be hoisted to surface, the company said.

An innovative laser navigation system designed by the Herrenknecht subsidiary, VMT Group, using target units mounted on the SBR and lasers connected to the shaft wall, was used to keep the machines on track.

Herrenknecht, with its experience as a technology leader in mechanised tunnelling, developed the SBR for the mechanised sinking of blind shafts in soft to medium-hard rock. Based on the proven technology of the Herrenknecht Vertical Shaft Sinking Machine (VSM), the SBR offers improved safety performance compared with conventional shaft sinking methods while also achieving higher advance rates, according to the company.

The geological conditions at Jansen, however, were anything but easy. At a depth of around 450 m, the SBR encountered a layer of extremely hard competent rock causing excessive pick wear and low rates of advance. To overcome this and some further hardness challenges, the cutting drum was upgraded to a hard-rock cutting drum and torque output was doubled.

Because an existing high-pressure underground waterway, known as the Blairmore aquifer, posed a risk for water ingress into the shaft, ground freezing was executed temporarily in 2011 by BHP to a depth of approximately 650 m.

A major success in this difficult geology was the use of a mechanical ring erector, which allowed the installation of steel tubbing segments with minimal risk to personnel and a high degree of accuracy, according to Herrenknecht. The steel liner rings were installed through the Blairmore aquifer to assist in the development of a composite steel and concrete watertight liner in both shafts.

Since the project-specific design changes at Jansen required modifications to the SBRs, Herrenknecht, together with contractor DMC Mining Services, refined the SBR technology over the long term. The result is the second generation of Herrenknecht SBR technology.

As an example, the second generation SBR is equipped with an additional stabilisation level that allows the fixation of the SBR centre pipe on both ends. This ensures a stable transfer of the reaction forces from the cutting process to the shaft wall without movement of the machine – even with fluctuating excavation diameter of 8-11 m, as encountered at the Jansen potash project.

In addition to an improved filter system, a new design of the PNM system was installed in the second-generation machine, which results in a higher degree of separation in the suction tank itself, allowing wet material and even water to be handled.

Martin-Devid Herrenknecht, General Manager Mining at Herrenknecht, said: “The technical development of the second SBR generation is based on the lessons learnt from the Jansen project.” Two SBRs of this generation are currently in operation in Belarus and achieving good performance as a result of the improvements made, Herrenknecht said. “This pioneering approach is certainly a game changer for shaft sinking in soft and medium-hard rock, impacting the whole mining industry,” he said.

After the successful excavation at Jansen, another task was to be managed: the disassembly of the huge machines in the deep shafts. To remove the SBR from the shaft bottom, it was necessary to reduce the weight of the machine from 390 t to 340 t. This was achieved by stripping all components off the SBR that were in the excavation chamber. Both SBRs were safely extracted from the two shafts at the Jansen potash project in May 2019.

The Jansen potash project, located approximately 140 km east of Saskatoon, Saskatchewan, is a BHP-owned future potential potash mine with an expected initial mining output of around 3-4.5 Mt/y with valuable expansion options.

BHP’s Jansen potash project set for early-2021 investment decision

While uncertainty remains around the construction of BHP’s Jansen potash project in Saskatchewan, Canada, the company, in its September quarter results, confirmed it is still spending money on the asset prior to making a development decision.

BHP said the Jansen Stage 1 potash project will be presented to the board for a final investment decision by February 2021. The currently Stage 1 plan, which is in the feasibility study stage, involves building out initial capacity of 4.3-4.5 Mt/y of potash, with expansion optionality.

The miner has, so far, committed to spending $2.7 billion on the project. This is expected to result in the excavation and lining of the 7.3 m diameter production (975 m deep) and service (1,005 m deep, pictured) shafts – sunk by DMC Mining using Herrenknecht’s Shaft Boring Roadheader – and the installation of essential surface infrastructure and utilities. The overall Stage 1 project is expected to have a capital outlay of $5.3-5.7 billion.

In the September quarter results, BHP said in order to make a final investment decision, work on engineering to support project planning and on finalising the port solution is required. The BHP Board has, as a result, approved $144 million of spending for these activities, with an additional $201 million in funding set aside to further de-risk the project. The latter is focused on the mine’s scope of work, advancing other engineering and procurement activities, and preparation works for underground infrastructure, it said.

“This will enable an efficient transition of the project team between the study and execution phase, should the project be approved,” BHP said, adding that the release of funding to the project will be staged over this period.

The company, meanwhile, gave an update on its South Flank iron ore development, in the Pilbara of Western Australia, with CEO Andrew Mackenzie saying the project was 50% complete, with all major items on schedule and budget.

South Flank, which is expected to cost $4.6 billion to build, is set to replace production from the existing Yandi mine, which is reaching the end of its economic life. BHP is targeting first ore extraction at the operation in 2021 and expects to ramp up to 80 Mt/y of output.