It's a shame you missed the rest, although your description of sand and pebbles in the roof does hint at why bolting that floor-collapse was so important. Ironically the cartgate section is easily the most stable part of the trade route! The 'squeeze' under the first stone stemple is only a squeeze because loads of shale grot from the floor-collapse landed there. Dragging the bolting kit through was bad enough, without us resorting to taking in shovels too, so if someone could spend a mere fifteen minutes on a future trip just digging that rubbish out, it would be a great help, and it wouldn't be a squeeze no more - there's plenty of room in the floor-pit you traverse over, as that's where the rest of the collapse is. There used to be as short downward passage there, with digging potential, but it's not there any more. And that stemple weighs about 200kg, so you really don't want it on your shoulders as you pass through!