SHAFT SINKING
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 DMC, refined the
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 Jansen.
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, Herrenknecht said. This next-generation
machine also came with 600 kW of extra power
compared with the first generation.
Martin-Devid Herrenknecht, General Manager
Mining at Herrenknecht, said: “The technical
development of the second generation SBR is
based on the lessons learnt from the Jansen
project.
“This pioneering approach is certainly a game
changer for shaft sinking in soft and medium-hard
rock, impacting the whole mining industry.”
After the successful excavation at Jansen,
another task was to be managed: the disassembly
of the 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.
Ahead of schedule
Two second-generation SBRs were already in
operation at IOOO Slavkaliy’s Nezhinskiy potash
project, in Belarus, while the equipment
dismantling at Jansen was ongoing.
That project, using two SBRs to sink two shafts
down to 750 m depth, with freezing required to
160 m depth, has broken Belarusian and European
sinking records.
Top maximum daily performance was around
7.4-7.5 m/d, while development rates of 144 m
and 138 m (with sequential shaft lining) were
achieved in the month of April 2020.
Jochen Greinacher, Managing Director of
Redpath Deilmann, Slavkaliy’s contractor and the
company behind such SBR sinking rates, says that
April record, in particular, was a big achievement.
“That was shortly before we achieved the
station level, so we had no opportunity to beat
that record,” he told IM. “But that is almost 5 m/d
on average, which is something to be proud of.”
Despite there being issues during the shaft
freezing section to 160 m depth, and the
occurrence of weak rock, and water ingress in the
next 160 or so metres of sinking, he was happy
with overall performance.
“When we talked last time (in July 2019), the
SBRs were in the freeze section, and then we had,
due to the weak rock and water ingress,
geological problems below,” he said. “At this
point, we had to leave the concept of
simultaneous excavating and lining; we had to
lower the forms into the cutting chamber and
reduce the height of the forms from 5 m to 3.2 m
which, of course, reduced the available cutting
time and thus performance.”
In that section – from around 160 m depth to
330 m depth, with the changed procedure and
methodology – the best performance was
achieved, according to Greinacher.
“Not so much in terms of absolute metres per
days, but in the respect that, even after departing
from simultaneous excavating and lining, we
achieved close to 4 m/d on average over a long
period of time,” he said.
The record April development numbers were
achieved in salt rock-type conditions, Greinacher
explained.
“From 500 m down – when we had already
reinstated excavating and lining at the same time
– we were mainly in the rock salt and that is
comparably simple; the sidewalls are stable, no
water comes in and the rock has very
homogeneous conditions,” he said. “That is where
we then achieved the 144 m monthly figure.”
It should not be forgotten, these latter records
were achieved during COVID-19, when social
In August 2018, two blind shafts at BHP’s Jansen
were completed to depths of 975 and 1,005 m,
respectively, using Herrenknecht’s SBR
technology
distancing was in place on site, fewer people were
in the cage and masks were being worn.
“It didn’t really impact production,” Greinacher
said of such restrictions. “At the same time as all
of this was happening the routine got better and
fine tuning was taking place to improve performance.
“I wouldn’t say COVID-19 had a negative impact
on production.”
Asked about current progress on the project, he
said: “We are just in the final stages of lining the
stations. We ended up carrying out the station
excavation with a little roadheader (a Voest-Alpine
(now Sandvik) AM-50), which wasn’t in the
original plan, but performed very well.”
The original plan was to drill and blast these
stations, but with the border between Belarus and
Russia closed due to COVID-19 restrictions and no
domestic supplier of explosives in the country, the
company instead used the available roadheader.
“I think we have another month or so ahead to
complete the reinforced concrete liner of the
stations,” he told IM in mid-July. “Due to the fact
we only had one roadheader, we completed the
sinking in one shaft at a time, including the sump,
and then backfilled it again with loose material,
which you can get out quickly by using the PNM
system of the SBR. On the other station, there is
still the sump to sink and the loading pocket area
to excavate.”
The company then needs to equip the shaft and
install and commission the skip hoisting system.
After that, the lateral development work can start,
probably early in 2021.
Even with all this work ahead of it – and a slight
delay to the original target of starting the shaft
sinking in January 2019 – Redpath Deilmann is
well ahead of schedule, Greinacher said.
72 International Mining | SEPTEMBER 2020