Working in sand... need advice

Hey guys. I am new to sandy soil and am having a real problem doing my job.

In the drainage business we dig something called a starter hole. In order to connect a tile pipe to a tile pipe main, we dig a short trench 30" wide, 2-3' deep, and about 10' long. From here we can install a connector into the main, connect a pipe to it, and then backfill. In clay its easy. Figure about 3 minutes per hole for a skilled operator.

In loose water sand its impossible. The two issues are water pouring in at about the 30" depth, undermining the trench walls, and speeding hole collapse.

Tried a bunch of different techniques including 2 excavators to bale and dig together. but nothing works.
By the time you give up, you have a hole as big as a small house, but only 24" deep, filling with water and sand as fast as you can bail it out. Whats really interesting once the hole gets wide, the sides start to sink, and the bottom starts to rise. Without any soiling falling into the hole, it gets shallower. Standing in the hole, you can feel yourself rising. Its wacked. So getting the trench bottom graded right is not going to happen.

I was thinking a trap bucket or a tilt bucket might help. Dig the trench with sloped walls and a narrow bottom.

I would listen to any advice anyone has

Thanks

Well points/spears is the only way to go. Dewater the the ground before excavation. It's a bit slower but pays big dividends over the job time plus you should be able to charge the client to do it.

Yupp, gotta get rid of the water!

The main should pull the water table down to the bottom of the pipe and make the sand dry enough to work.if it's a old existing main is it so over loaded so it's not working. If it's a new main did you installed is it deep enough, and you may need to give it time to pull the water table down to make it easier to dig your lateral starts and put in your tap tees.

You could 2:1 slope it or lay it back farther but you will be wide at the top could you dig off to the side to get the water to run over to a deeper hole with a pump in it to to try and keep the water down I have done that and put a little bit of rock in the bottom of the hole set the hose on it then throw more rock on top of it make a little leach pit then you could stand and work in the hole

Well points or a kelly well would work best in that situation. Soupy sand is no fun.

02SILVER said:

Well points or a kelly well would work best in that situation. Soupy sand is no fun.

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FYI don't google kelly wells. Its way off topic.

Haha I googled and haven't found a satisfactory answer yet!

I might be wrong, but i think a kelly well is a perforated pipe surrounded by clean stone. I would think that would be hard to construct with the current ground conditions and less than ideal to put in the middle of a field.

Water sand is a pita.....that shrit defies the laws of physics.

Ed

If wellpoint dewatering is not available or too expensive,try using a trench box and drain rock.

72hayes said:

If wellpoint dewatering is not available or too expensive,try using a trench box and drain rock.

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In real runny sand it won't work. the sand boils through the rock. BTDT