PROJECT DESCRIPTION

As part of the development of a new excavation area at Bardon Hill Quarry, Aggregate Industries required a slot to be excavated through the uppermost two benches of the original quarry. The slot was to enable Doppelmayr to install an 850m long RopeCon suspended conveyor across the former quarry, which will be used to transport 12Mm3 of overburden from the new quarry into the former excavation void over a 14-year period.

CHALLENGE

Whilst a slot was required to be constructed through the upper rockface high up on the existing rock face, the practicality and logistics of how to safely excavate the rock, in such a precarious position, had not been resolved. GWP was tasked to assess the ground conditions and the rockmass, and develop a safe working method to access, excavate and stabilise the slot in advance of the suspended conveyor being installed.

SOLUTION

GWP

• supervised the site investigation including vertical and sub-horizontal boreholes and laboratory testing;
• undertook UAV survey of the faces to collect discontinuity data using photogrammetry;
• used the discontinuity data to assess the rockmass characteristics and determine the type and extent of stability issues as the slot is excavated.
• developed a safe working method to excavate the slot some 30m below the crest and over 165m above the quarry floor.
• designed and supervised the rock netting and bolting required to stabilize the sidewalls of the slot.
• undertook 2D and 3D rockfall assessment to develop a design of the rocktrap bund required to protect the haul road from the risk of rockfall.

IMPACT

These works enabled Doppelmayr to install the RopeCon suspended conveyor to transport the overburden from the new quarry into the former quarry void. Furthermore, the new 4m high rocktrap bund alongside the haul road, mitigates the risk to plant and personnel from rockfall.