Godstone Sinkhole

If it is caused by a burst water pipe the water must be carrying the sand out somewhere to create the void. Either it is filling another empty space (a mine down stream or out into a surface water course). But where?
 
In another forum someone with considerable local expertise identified on a late 1800s map the site of the current sinkhole was indicated as "entrance to underground sand mine". So Seems to be a smoking gun there 🤔 🔫
 
There is considerable evidence of historic sand mining in the Godstone area, some of which are documented in the Chelsea Speleological Society records (these are not by the present collapse), but other unrecorded mines are likely to be present. The old six-inch topo maps do indicate the entrance to an old mine close to the collapse, but the extent of the mine is not known. It is likely that the leaking pipe has saturated the local soil, weakening the rock, and possibly triggering the collapse of one or more old sand mines, with attendant flushing of the weak unconsolidated sand from beneath the road along the line of the pipe. Finding out where the water has gone would help identify the cause of the collapse; it may have gone into the back-filled quarry to the west of the village. It is not, as some media outlets have suggested, anything to do with dissolution of soluble rocks, or old chalk mines.
 
And thanks to Jenny Potts at the British Caving Library for digging out some of the Chelsea SS records for this area. She dug out the relevant journals and set me scans quicker that it would have taken me to walk home and dig out my own copy! The BCL really is a fantastic resource and Jenny and Mary are a veritable mine of information.
 
I’d be curious to see exactly how extensive those passages are.

Feels a bit surreal that there’s this whole hidden network quietly sitting beneath the road.
 
A bit more detail here
and in the Independent (mentions Andrew Farrant)
 
In the days of coal fired power stations, there would be a large and cheap shortage of fly ash, which could've been pumped down as a slurry and sets hard.
Not sure what the preferred "gloop" to stabilise something like like this is these days?
 
In the days of coal fired power stations, there would be a large and cheap shortage (surplus?) of fly ash
When pouring large thicknesses of concrete, we used to replace a percentage of the cement with pulverised fuel ash as it set much more slowly and avoided overheating and consequent cracking. An alternative was ground granulated blast furnace slag - now probably just as hard to find as fuel ash. Maybe it's imported now?
 
Sorry... "no shortage " is what I meant. Doh!!!!

I've used retarding plasticiser in mortar and aware of "Extratime" for plaster (although never used Extratime), but I think you'd get through a lot of little sachets of Extratime pouring the quantities needed to underpin that sinkhole 🤣

Didn't know blast furnace slag worked also
 
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