Twinwall Pipes In Cave Digging

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The Old Ruminator:
At Vurley we used 7m of 1m concrete pipe. That basically because they were lying redundant in the next field. The dig also had a sturdy hut a few metres away so these seemed the best reason to dig there. Mostly in my long digging career we have resorted to scrounging for free the materials that we used. We also got 60m of free scaffold tubes for Vurley. Now we have three shaft digs going and it was time to try another approach. We came across Twinwall plastic pipe. By sheer luck a contact in the caving world got us about £3,000 for nothing as the pipes had been used in a major construction job and were then discarded. New Twinwall comes in 6 metre lengths at 900 mm , 750mm and 600mm internal diameter. The Twinwall 900mm cost £1,200 new. One end has an overlapping flange taking the external diameter to 1020mm. ( best remembered if using shuttering ). Twinwall cam be carried or rolled, cut and takes impact screw bolts. We got enough 900mm for the three shafts plus some 600mm. All had been cut for use to about 1.5m length which suited us fine. A club member delivered them to site in his camper van. The images show the process of shaft construction using Twinwall.

At Vurley using concrete pipes which needed a machine to put them in place. Ultimately the machine cost us £1.500 for excavation and pipe fitting.

Stage one of the excavation at " Ramson's One ".

Our prize from the forum competition at  "Ramson's One ".

The Old Ruminator:
Shoring in place at  "Ramson's One ".

The pipes arrive at " Ramson's One ".

Preparing the shaft for pipe insertion.

Getting the pipes in.

We forgot the extra 20 mm for the flange.

The Old Ruminator:
Pipes finished at " Ramson's One ".

Fitting the internal ladder. If using through bolts leave access to the outside of the pipe. Drill driven screw bolts worked and the top was through bolts in stainless steel.

Preparing for the concrete cap and gate.

Setting the gate ready for concreting. The gate came free made from material thrown out by my local supermarket. We decided on a small access for security and ease of fitting . In any case we were constrained by the frame already existing in the ex display unit.

The concrete cap and gate completed and the quadpod's job done. It is now at " Ramson's Three " which is already 4 metres deep.

The Old Ruminator:
The gate. On the underside of the cap are two inset U Bolts for rigging.

Inside " Ramson's One " showing the Y hang on the U bolts.

" Ramson's Two " in progress.

Pipes set aside for " Ramson's Three "

Cost has been kept to a minimum by scrounging and help.

The pipes and ladders were free. The gate was made up by a " Tuesday Digger ". All work has been done by hand but the prize quadpod was a great help and continues to be so. So far the cost incurred were for aggregate and cement. About £70. Some of my images are numbered to maintain a hardback record of the work which is estimated to take a year in total. " Ramson's Four " is also an ongoing project giving us two days a week work. Well most of us are retired.

Weight is a big advantage of twinwall; the Wardlow Sough pipe was manhandled into place by about half a dozen people IIRC whereas had it needed to be concrete piping, I don't think we'd have been able to get machinery near enough lift it into the hole!


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