Pit Problems

Yeah, but there it rains rocks!

Same is true in the pesky small clay pits here. Get to a point of severity of angle and even rock will fluidize. Eventually the pit walls slide to a softer slope and becomes less a issue.

it's the angle of repose. What mother nature seeks in a given material.

I can not guess how many tones of material fell in the small slide but I remember in the early 70's at Kaiser I was on a D-9 and waste dumps are always moving and I was putting a ne lift on and a 200 ton truck would dump and that is not a huge amount of rock when you are putting a 10 ft lift on a waste dump

^ I had 4 50 ton terex trucks bringing me rock at Cowlitz falls, I had a 9L to push and it was maybe push push push and wait for the next truck on a 45 minute round. Hard to stay awake and the rotten rock would not tolerate a bunch of massaging. We were building that little island in the lake here from rock taken from the dam cut. https://goo.gl/maps/RtXZhDWuG2vrYqZX8

92U 3406 said: I've spent a fair amount of time in shovel pits. There was a rule that you had to be a certain distance from the working face. I want to say it was 2x the face but I can't remember. Haven't been in a mine in about 5 years. Click to expand... We used 1.5 times the bench height but basically the same thing. In really unstable areas Mine Ops would build a berm maybe 5m away from the toe of the bench to (hopefully) catch any stray rocks that came crashing down.

Nige said: seen the photos of Freeport in Indonesia, and now seen the photos of this one. All of them involved the movement of major league amounts of material (10+ million tonnes minimum). Click to expand... I don't know a ton about freeport Indo though did work for freeport for a while just as they started going underground block and cave in Indo. We'd get news articles and updates about Indo and I believe they went to almost all remote muckers ran on the surface pulling from the draw points because mud rushes out the draw points were so common. Is the ground in Indo just that loose and unstable?

Christy Minerals owns most of the clay pits here, has independents work those pits, have seen or heard there are changes coming to MSA Rules on depth to wall angle to bench width and height requirements at least on these mines.

Just received a text from a friend, the slide in the pit has not moved any more and they are going to open the pit again.

Just a couple of quick notes to help add to the info given. Nige said: A bit of research reveals that both open pits at the Highland Valley operation have been suffering slope stability issues since the late 1970s, so I will hazard a guess that the situation is not going to be new to them. From a report that's over 10 years old......... https://www.tandfonline.com/doi/abs/10.1080/1389526042000263324?journalCode=nsme19 Click to expand... There are actually 5 pits at Highland Valley. 3 of which are currently active. The Valley pit was the only put affected by the slide, and the other 2 remained in operation. The Valley pit is the main pit though, so it was a considerable slowdown for them. Nige said: To give a better idea of the scale of what came down the bottom RH corner of the 2nd photo and the 3rd photo show parts of the same area. That's a 793 truck and I think a P&H 4100 shovel partly buried. View attachment 274514 Click to expand... The Freeport shovel is actually a 2800 or smaller. You can tell by looking at the back of the house roof. The 2800s and down used to have the raised rear section visible across the rear of the house roof. The 4100s have never had that feature. Nige said: Couple of interesting videos from Bingham Canyon. First one if I'd been the driller who put that hole pattern in I'd have been crapping myself thinking that my drill could have been on top of that lot..!! 2nd one is a time lapse of the 9-month process to dig through the bottom end of the slough and re-establish the haul road down to the bottom of the pit. Click to expand... The two slides pictured at Bingham Canyon were actually separate events on different sides of the pit. The slide that was shown beneath the drill pattern was a second slide in 2021, years after the large one that was featured in the time lapse video that happened in 2013. Not trying to step on toes, just help expand the information presented.

I heard that a few days ago Highland valley had a 10 bench slide come down. Shovel in pit had rocks over top of tracks. No pictures as my contact is on holidays.

Are seeing typical fractured rock degradation on older bench profiles here. Highway cuts, deeper quarries. Extensive site set backs. When performed the original blastings’ the rock shatters further into wall, blaster I know noted such, over time freeze thaw fractures deeper and the walls fail, he suggested to the Highways group engineers here to revisit benches at least biannually to validate that extension of fracture for remediation. MSA is after miners here to extend benching further back as have had narrow escape events in the clay pits.