draughting sand?

[ian mckenzie]

Anyone have any experience with airflow permeating apparently solid chokes of sand/silt?  I would have thought it unlikely, but there's a dig here with no airspace that feels cool and there's no breath condensation (common throughout the rest of the cave, which is high, cold and relatively humid). 

 

[graham]

Willing to bet that there's a tiny airspace that you haven't seen yet.

 

[AndyF]

When we dug Rubble Rift, we had to pump air to the face to avoid suffocating. Suddenly, we didnt have to do it anymore.. the tube was still 100% silt filled, and we couldn't find the source of the air, but it was there alright..

We learned it took only the tiniest fissure or gap carrying air to keep a point "fresh"..

8m further on we broke into a chamber.....

 

[Tony_B]

A while ago we used to dig a completely sand-filled passage in Dan-yr-Ogof. We became convinced there was a draught, and the air quality never seemed to deteriorate, so we took in a joss stick and were amazed to watch the smoke 'blown' down the digging face and out behind us. Sadly we had to abandon the dig after a narrow miss with a boulder that was embedded in the sand, so never proved the point about the draughting sand.

I recently went back with a hot-wire anemometer that showed a resounding '0.00', but I have other witnesses to the joss stick incident, so it wasn't a figment of my imagination. 

 

[ian mckenzie]

This particular dig might just add 150m depth to a 500m deep cave, so the question of draught is a significant one.  Thanks for the input...

 

[SamT]

Sounds like you need access to a hot-wire anemometer (or infact some joss sticks)