Aug 2, 2011
I wasn’t 74 buckets from getting in but I’m 74 buckets closer to being in. Not just buckets of mud either..We took out ten buckets of just rock from the replenished cairn. Replenished after the mud slump from behind the east wall ten (?) weeks ago. It allowed the rock pile to settle down replacing the mud as backfill. We moved the rocks up to the surface to make room for two boulders from the dig ten feet below. My bedrock floor, marble, is dropping straight down instead of the 70degrees East incline of the geologic strata. The boulders were my steps to get me out of the hole as each bucket was moved up to the lifting cable. The boulders had to be replaced by steps. I was blessed with 2 small anomalies on the west wall that allowed me, with some strategic shaping with the pruning saw, to hold the west end of the steps. The east end fit into cracks in the rock pile on the east side. Rearrange the rocks a little bit, cut everything just the right length and just the right shape, and, presto!, 2 more steps fit into the rocks as we descend down this sink-hole into the unknown chambers waiting below. The upper step wasn’t quite perfectly horizontal, but it will have to do. If it’s a slipping problem I can put a slight wedge on it.
Now in touching on safety, my chief concern this season has been shoring up the west wall from what started out as shored rock and clay, but is now boulders too big to move on the north end. I need to shore over to the southward sloping wall. The south wall not only slopes angling down to the south but also slopes down to the west, striking SE to NW, and so I can lock the south end. I can lock the south end of the shoring from coming out but not down. Without backwards pressure, the shoring planks want to settle down and lose their tight grip on their north end. Creative cross-bracing over to the rough marble of the west side that keeps upward pressure on the east wall has helped. The only back-pressure I’ve gotten is when thirty buckets of mud flowed out from behind the wall one day, and my rock cairn settled down until a big rock wedged itself somewhere behind the wall. The rest of the rocks slowly (over weeks) settled into place and things seem to have stopped moving.
Now I have come down to this big boulder, 4’ long. My wall is now sitting on that, I am digging down alongside, about 2’ so far, and have to ask myself what is this rock sitting on. The one above is sitting on it, and the one above that is sitting on that one, and there are two or three more up to the bedrock of the NW corner, twenty feet above, just below the collar where the culvert to the surface is attached. (Wow! What a wonderful poetic sentence!)Could this rock just tip over, falling out of the east wall onto the west side, loosened by my digging, opening up a huge gap at the bottom of the east wall, and activating the sink-hole? Now, I have had to ask this about every rock above this one and the answer so far has been, “No, it’s sitting on a bigger one.” But, this one is the biggest, so if something goes wrong it’s a bigger wrong. What these boulders appear to be are pieces of a dike broken by faulting. They seem to fit together and are not much moved from the original placement in relation to the marble. The dissolution of the marble alongside the dike allowed the fault fractured rocks to fall down into the descending passageway, and opened up a hole for the North side talc seam to wash and slump down over the rock rubble, leaving the larger pieces of the dike practically in situ. Which all may be true but it still doesn’t tell me what it is sitting on, and if it is al all inclined to stay put.
At this point, the upper corner of the south end is locked behind the sloped ceiling (south wall), chinked with a wedge rock. The north end at dig level is pointed with mud back under the point. I haven’t found the bottom in the middle. I am encouraged by the fact that the rock seems to be right where it has always been during the whole process of cave and sinkhole formation, and collapse to the surface. If it went through all that and stayed put, perhaps it will suffer my shoveling in the same spirit. I think I’ll add a cross brace anyway, a sturdy one. Here’s hoping my Mistress will be kind to me!!
The last day of July was a great dig. Laptop and cameras up and running and we got some video on the hard-drive. Hole ddrying out and I can even stand and dig. I can’t wait to see what the next 100 buckets will result in!
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