How to Brace

I'm trying to figure out how to temporarily brace the walls of a 4' deep pit that measures 10'x15' cheaply (hopefully with scrap lumber and plywood I have on hand). Its like beach sand so has a tendency to cave A LOT and its not going to be filled for at least a few weeks which could mean hours of digging if I don't prevent cave ins. I'm not going to be working where it could be dangerous (near the walls) so I was thinking about just putting 2x4 stakes in the ground and plywood behind it. What do you think?

Any insights are greatly appreciated.

In case you're wondering, its for a climate battery/solar geo thermal heating & cooling system.

I would do the stakes and plywood, and then brace the tops of the stakes, either diagonally across the corners as far as your lumber will reach, or straight across the 10' dimension in the middle of the span, with 2x4s scabbed together to reach (as long as you have some that are close to full length). Every stake probably needs to be braced, or tied to one that is. A line of 2x4s flat side horizontal around the top inside faces of the stakes before other bracing will help significantly to keep everything lined up. What size range is your scrap lumber? How many long pieces do you have? Unless there are a number of longs near 8', you may have to make do with a short diagonal brace back into the sand floor for each stake. I would not make such braces less than about 4' in from the wall, for stability.


How are you planning to install the permanent sides of the cavity? Will the sand in a couple of weeks collapse as soon as you remove the temporary sheathing? Or will there be any structure at all in there?

Thanks for the ideas. No structure. I'm just laying tubing in the pit and then its just going to be backfilled.