What do you use for trench compaction

[terman]

Hi for trench compaction. 160mm pipe at 1.2 to 1.5 M with 400mm trench width.

1/ Is it necessary to use a trench whacker machine for the
10mm pea gravel below the drain. Or home made alternative. i.e heavy wooden post

2/ Above the drain upto 300mm I believe the gravel and backfill should only be gently compacted

What to use.? heavy wooden post

3/ What to use for compacting clay above this level in 300mm layers, should I wet the clay to make for easier compaction.

trench compator or heavy wooden post?

[seanandruby]

just put the shingle in and slice with a shovel, walking on it will compact it. lay your pipe, bring shingle half way up and slice along the side of the pipe with a shovel ( do this gently or your pipe will raise up ). top up with shingle 100 / 150 above pipe. now back fill in 150 layers and use a Rampactor to compact, or a plate wacker, definitely NOT a lump of timber.

[terman]

Thanks s&r

Do you know the standard width of a trench compactor, the petrol part at the top seems quite wide not sure it will fit down the trench.

[seanandruby]

if your trench is too deep for rampactor it should be battered, or shored up. how deep is trench? max working depth 1200 after that seek professional guidence. that was the benchmark we worked to. Now there is no restriction its what you deem to be safe , i e 50 ml.

[terman]

Hi Sean, Trench is about 1.2 to 1.5 M. I expect by the time I have added 300mm of pea gravel + 160mm pipe and 150mm of clay I will be compacting at about 900mm. I presume I could add a little more pea gravel or start compacting a little higher. Should I be OK with this depth with a standard trench wacker with a trench width of 400mm.

[seanandruby]

pea gravel is expensive i would go with 150 shingle/ pea gravel,. 300 as dug cover for your first run, then 150 layers thereafter.

[terman]

Thanks again sean

Building inspector has changed his mind on bedding in pea gravel and said to

pea gravel upto bottom of pipe, then concrete upto 150mm above pipe. This is due to the distance away from the house foundations.

What mix would you use for the concrete, can I use the 10mm pea gravel in the mix as I have already had 2 ton delivered although some can be used for the bedding.

Regarding the compacting I assume I can just asdug above the concrete and start compacting 300mm up in 150 layers as you said.

Thanks for the help.

[Tony McC]

Yes: use the 10mm gravel and mix a ST4 concrete as described here

[terman]

Thanks Tony

All the help here has been excellent. Layed my first run of 160mm pipe today and water tested. Seems to be working a treat, so your answer on the concrete was well timed.