Geotech New Zealand l Geotechnical Engineers Blast Scary Lucy

Ridgeline Mining ProjectScary Lucy

RMP A14 Mining Block Ch5485 to5500m L27. Scary Lucy and associated worries

View of the block named ‘Scary Lucy’ prior to restarting the deconstruction of A14-E2 at the end of Oct. A crack has developed and is being monitored more closely. Beddings and defects on the southern side bring uncertainty as to how to which way to approach.


The progress of the moat in momentarily interrupted to allow for a better stabilisation of the block


Geomos prims are being dis-intalled and re-installed before each rock breaking session. It becomes hard between these interruptions and the bad weather to acquire enough data on the block movement. More site-based monitoring is required, which implies multiple daily observations

of the cracks and signs of movement


The geotech PC300-mounted man-cage


It is decided to rock-break and excavate the block as quickly as possible before further creeping of the base is observed.


Continuing movement is however observed once the top 3m are removed. We are left with an approx 60t block, detached from the escarpment along a crack that is becoming more and more visible with the slightest deconstruction-induced disturbance. The moat is not deemed capable of

hosting the hole rock mass at once. Further stabilisation is required.


4 holes are drilled to allow the installation of 32mm fully grouted reidbars, themselves anchored to shorter ones mounted into competent rock, to the East. Once these in place, intense rockbreaking is undertaken, but progressing further south becomes impossible with the too short, too

narrow and shallow existing moat profile.


To progress the moat again, the rock needs to be further stabilised as two of the 4 dowels have been dislodged during rock-breaking activities and an approx 45t block with a rear crack more prominent than ever still remains. It is decided to recycle RXI200 rockfall barrier net and ropes

to wrap the boulder and tie it back


Two excavators (using boom and track base dissociatively) and one drill are timely orchestrated to perform the tensioning of the 4 cables onto added roof bolts


Ant Black inspecting the positioning and tensioning of the cable. Highlighted in pink dazzle are the first signs of the birth of Lucy’s monster baby, indicating further undermining of the block)


With the block stabilised, the moat can progress by another 15m and gain in depth and width. We are now in position to eliminate our worries.


After a small amount of rock breaking the block blatantly detaches itself and the stabilisation work takes over the load.. And yes, surprisingly enough, it sustains it!


only just… for the early dowel located too close to the edge of the crack


The block after the blast


Viewed from the North


And the final crack at it. Less proud she stands…let’s remember the block slowed down productivity in that area for nearly two month and cost the project more than $70K. An expensive piece of sandstone.

Geotech New Zealand l Geotechnical Engineers Blast Scary Lucy

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