DM Civil

DM Civil’s Tesmec TRS 1475 Trenching Rock Saw essential equipment for mine pit

June 2020

DM Civil were initially contracted to undertake several kilometres of drainage trenching surrounding a mine pit dewatering pond at amine site in the goldfields using DM Civil’s 95 tonne 600HP Tesmec TRS 1475 Rock Saw.

The existing near surface material was extremely hard and site management were extremely impressed with both the machine’s performance and also the our crew’s work ethic.

Senior mining engineers recognised that the use of the Tesmec TRS 1475 may help with excavation works as part of the primary development of a new lift shaft infrastructure.

The key issue was that the hardness of the subsurface material and confines of the work between existing stockpiles, mine pit haul road and mine site offices in the near vicinity precluded the standard drill & blast and bulk excavation methodology.

This standard approach would be too invasive to the mine’s operations and with potential harm to nearby existing infrastructure

Discussions between the mine and DM Civil resulted in a team collaborative approach to an extremely tight excavation, utilising the Tesmec TRS 1475, plus 36 tonne excavators and 30 tonne front end loaders.

The methodology was to undertake slot trench excavation, up to 3 metres deep then backfill and compact immediately to allow the next slot trench pass to be within 300mm of the previous excavation.

The works was to be undertaken included in 5 different flitch (box-out) levels. ,By  with gradually reducing overall perimeter sizes, to a depth of approximately 13.5 metres and with an 8 degree entry/exit ramp approximately 100 metres long left in place for access to future raise boring and concrete works.

Location, orientation, overall cut shape and time were all essential elements of the proposed earth works, with overseas specialty drilling, grouting & and raise boring contractors scheduled for mobilisation in advance of the earthworks being completed.

DM Civil mobilised two (2) teams of personnel to undertake 24 hour shift operation.

DM Civil in-house survey teams uploaded excavation design and individual trench cut route alignments into a GPS base station, which was linked with the Tesmec TRS 1475 GPS system.

This produced extremely accurate position, orientation and depth control essential to create a level and flat base for each flitch for the Tesmec TRS 1475 to undertake the next batch of slot trenches.

The 300mm wide by 3000mm deep “biscuits” of hard material left between each slot trench cut were easy work for DM Civil’s Cat 336EL excavators to snap off when undertaking the bulk earthworks.

DM Civil’s Cat 980 front end loader was the “War Horse” that uploaded and carted excavated material back up the ramp to a stockpile.

The trenched material was excellent material was, free of rock boulders because of the chain saw trenching process and was therefore later re-used as valuable backfill. to This was placed and compacted to fill a disused pond at the location of one of the shaft A-Frame back-brace footings.

The operation of trenching, immediate backfill, re-excavation, loading and carting of material to a stockpile was undertaken using a mixture of 12 and 24 hour shifts over a 14 day period.

During this time DM Civil also worked in conjunction with specialised drilling and soil anchoring contractors, who installed rock bolts and soil anchors to the vertical sided pit excavation walls.

The mine management was extremely pleased with the quality of the finished product, timeliness of the operation and importantly ability to re-use valuable trenched material that would otherwise be drill and blast boulder waste.

The GPS control to the Tesmec TRS 1475 allowed peg-less survey control of the excavation, which aided in the overall safety of the operation without the need for ground based survey personnel in the near vicinity of very large earthmoving machinery, with restricted visibility.

Trenching machine productivity and GET (Ground Engaging Tool) performance were greatly enhanced through the use of construction water, which also aided for trench backfill compaction and also pre-conditioning of the excavated material for subsequent re-use for the A-Frame footing earthworks. This also had the added benefit of controlling dust during the earthworks.

Overall, whilst the Tesmec TRS 1475 with its GPS control was essential to deliver the required project outcomes, ultimately, the teamwork between mine management, & staff and DM Civil personnel that guaranteed its success. The excellent use of interpersonal skills and cross fertilisation of ideas and solutions to problems, as they arose on site, was testament to the “Can Do” approach of both organisations and a truly rewarding experience for everyone involved.

The Tesmec TRS 1475, showcased in this video, was an essential element in delivering a successful outcome for this highly integrated project.