Category Archives: Mine

Artificially created underground spaces

Mine

Sand mine near Bearsted

Request from a developer to investigate and survey workings uncovered during site development works.

On 11 May 2022 we were contacted via the KURG website enquiry page by a contractor preparing a site for construction near Maidstone. They requested that we might help in urgently investigating a ‘sinkhole’ which had been exposed by their ground works excavations.


John Smiles and Pete Burton attended the same day to investigate the site and advise the contractor on what they might need to deal with before continuing with their works.


The sinkhole was a small, domestic scale sand mine cut into the locally abundant fine-grained construction sand of the Folkestone Beds laid down in the Cretatious. At least two other underground sand mines are known to exist in the immediate area.


Following the usual safety checks, an approximate tape and compass and photographic survey was carried out. This survey was then supplied to the contractor, ready for referral onto their design team to advise what to do next to make this minor working safe for the access roads and light industrial units destined to be built on the site before the end of the year. 


The likelihood is that the site will either be untopped – the tops of the chambers being no more than four metres beneath the current (recently modified) landform – and levelled with layers of compacted fill, or made good with foamed concrete or similar.

Whichever fate awaits this small mine will of course obliterate it, probably within a week or so.  

Mine, Other, Surface, Underground

Hucking Denehole, Kent

17th December Work started on this dig. An aerial cable was placed across the hole using the fence posts for support. A second lifting cable and ingenious pulley system was hung below this to enable the bucket to be raised and then moved sideways.
28th January After another early start 2 members who wont be named decided to take the exercise and walk the ‘short’ way across the fields to the dig. Unfortunately they took a wrong turning somewhere and ended up going completely the wrong way. They arrived about 1 hour after they left the car park. Progress was slow because the excessive amounts of wire in the hole and we even had to resort to using a car to pull it out. We didn’t get as much done as we would have liked to but we think we can now see the top of the chamber.
25th February Work continued and good progress was made despite the weather. We managed to remove lots of wire along with many old logs from the hole. At the end of the day the top of a small chamber was visible.
25th March Despite a promising start the top of the chamber visible last time has so far been a bit disappointing. Although just big enough to crawl into it seemed to be very small and almost entirely back filled. However after several hours of digging a small entrance was found about 120° from the small one. Clive was the first to enter and explore this, despite an initial concern about the quality of the air. The chamber turned out to be larger then expected and unusual in design as it turned through 90°. This chamber is about 20′ long by about 6′ wide with a height of about 10′. There is another small chamber off the back of this which looks as if it may connect to the small chamber first discovered. For more pictures click here.
15th July It was amazing to see just how much growth had taken part since we last visited. Nature seems extreamly keen on reclaiming the hole and the surrounding area. Despite further digging the only thing we found was a mouse in one of the holes made to probe for the third chamber. After some deliberation it was decided to persue the dig no further. The bats will have to make do with a single chamber. The picture shows the spoil heap from the dig. For more pictures click here.
Mine, Surface, Underground

Burwash

3rd July Initial dig by farmer using JCB. This reached down to about 8′. The remains of a previous exploration trench could clearly be seen cutting across the new one. We fenced off area to make it safe for cattle in field.
7th August We removed some slippage that had occurred since the last dig and explored the bottom of the hole to locate original shaft position. Temporary scaffolding was placed across the top of the hole to facilitate hauling and removal of infill. Work started to construct the ‘tower’ inside the hole. This is backed with corrugated steel sheeting cut to size and slipped (or bashed) behind the tower frame. The area around the shaft was started to be backfilled.
11th September A permanent frame was erected above the shaft to allow petrol driven winch to be installed. Work continued to dig and backfill the area around the shaft.
25th September Continued digging and backfilling area around shaft. Various pieces of wood from the original shaft were excavated.
9th October More digging and backfilling. Added another 5 feet to the depth of the shaft and passed through a layer of limestone which is clearly visible.
6th November We had to haul all the equipment down to the dig site in a wheelbarrow due to the very soft ground. Despite this and the wet weather we managed another 5 feet. The excavation is now in the original shaft cut through sandstone.
20th November The digging continued despite the freezing temperatures and the present depth is now 35 feet. The top has been extended and back filling is happening around this to make sure any surface water flows away from the shaft and not into it. Loads more wood from the original shaft has been recovered and the remains of the original timbers can now be seen in one corner the shaft
26th March The first dig of the new year saw us shuttering up the 9 foot of previously dug but un shuttered shaft. The weather was not very kind (it rained), but the farmer was and lent us his tractor to transport the shuttering and poles. At one point a gurgling sound from the bottom caused interest as all the water disappeared, but subsequent trampling in the bottom seems to have blocked it again.
3rd May Added about another 4 feet to the shaft and shuttered 3 feet. Although the weather was kind to us today, nice sunshine, were disappointed to see that water was entering near the bottom of the shaft and had formed quite a puddle by the time we left. Hopefully we have not hit the water table and this will have drained in time for the next dig. Still large amounts of old shuttering timber coming out, we have quite a pile now.
25th June Things don’t look too promising at the moment. Water is coming in to the shaft in one of the corners and seems to be settling at a constant level. Despite much prodding we couldn’t seem to replicate the gurgling we saw on the 26th March. When we left there was about 5 inches of water in the bottom of the shaft.
27th August Not much to report, more pumping, more digging, more water.
24th September Even with the pump running flat out the level of the water remained constant despite the dig continuing downward. By the end of the day the water was at thigh height.
8th October For the last push of the year we increased the pumping capacity by using a sump pump in the bottom of the shaft to pump the water up to the main lift pump. This necessitated having a generator on site as well as all the usual kit. Despite shifting about 60 gallons per minute we were still not making headway.
26th – 28th September 2008 After hiring a 3 phase pump the shaft was eventually pumped out and with a little digging the entrance to the mine workings were slowly exposed.
The workings could be clearly seen extending away from the shaft. The main route is in very poor condition and appears to be collapsed after a few meters. Side workings appear to have been worked out and bricked up. The workings are only visible with the pump running and quickly become submerged when the pump stops.
28th December 2009 This project has now been completed and no further exploration is anticipated in the foreseeable future. The final outing was to cap the shaft and tidy up the site. The water at the bottom of the shaft was at the highest level we have ever seen at 16.5ft. Together with a depth of 35ft to the surface of the water this gives a total shaft depth of 51.5ft.