Concrete canvas

[Adam2]

Anyone used this on here 

https://www.concretecanvas.com/

 

Am considering as an option to add stability to an excavation that will be about 3m deep x 4m wide and 70 degree slope. Will be backfilled in 5 weeks so only temporary. 

 

Price is not too bad and quick to install with no special tooling etc. 

 

Currently either that or trench sheets and some props set into concrete thrust blocks . This sheet option will cost more and take more time hence considering new fangled ideas 

 

 

 

[nod]

There doesn’t seem much point for five weeks 

[Adam2]

Without something being there the slope may collapse especially with heavy rain/wind as the site is exposed as at the top of a hill. The top of the slope is my neighbour's path down his side of the boundary. Limited room so the slop will be very steep and some lucky person will need to work next to it to waterproof the walls before we back-fill. Unlikely to collapse but I;m sure that was said many times before it did ?

 

Open to any other suggestions, my default option that both the ground workers and build co are happy with is below. This is more expensive that the concrete canvas (which my geotechnical contact says should be OK) option but is better understood/trusted by the teams who need to work near it.

 

Any other options of course appreciated - I was intrigued by the concrete canvas but that route may just take too much time to get agreed whereas the one below I can get done in 3 days.

 

[Mr Punter]

I think you would be better leaving temporary works design to others as it is potentially high risk and you are not skilled to do this.

 

You could expose yourself to all sorts of issues and CDM would come into play.

[Hobbiniho]

In the instillation guide for the concrete canvas it says "prepare the surface so it is well compacted, geotechnically stable and has a smooth and uniform surface" you say that it may collapse so it is not geotechnically stable, this stuff is for providing a quick cost effective protective top layer for streams, rivers etc it is not for shoring excevations, there are strict guidelines for working in trenches, if you cannot bench the excevation due to space constraints then you need propper shoring as your diagram shows.

[Adam2]

2 minutes ago, Hobbiniho said:

In the instillation guide for the concrete canvas it says "prepare the surface so it is well compacted, geotechnically stable and has a smooth and uniform surface" you say that it may collapse so it is not geotechnically stable, this stuff is for providing a quick cost effective protective top layer for streams, rivers etc it is not for shoring excevations, there are strict guidelines for working in trenches, if you cannot bench the excevation due to space constraints then you need proper shoring as your diagram shows.

 

It's a difficult decision and I agree I'm not qualified to make it. The geo-technician who did the ground investigation thinks this is OK as does an engineer at the product supplier but I'm a bit cautious so expect we will go with the shoring as per the diagram (which was the SE original proposal). I think I've found a decent source for trench sheets so this is coming down in price which is helping!

 

My reference to collapsing was really meant if there is prolonged bad weather at an inopportune time vs a substantial sudden collapse as per the recent house in the news on the Isle of Sheppy.

 

Anyway - a really interesting product but not one then that I'm expecting to use for this project unless we want to make some concrete furniture or other interesting garden feature ?

 

[Bitpipe]

When we did our basement excavation it was a hole about 12m x 13m at the bottom (3.5m down) and about 2m wider all round at the top to allow for the battering back. Soil was clay on gravel on chalk so not super stable but it was end of summer in SE England so quite dry.

 

Based on the ground investigation report, the SE specced the hole 'design'  but ultimately the excavation was up to the groundworks contractor and it was their crew who were working in the hole. I applied the EPS to the outside wall (at my own risk) and was more than happy when it was all backfilled with clean stone.

 

So I'd leave it to your groundworking contractor  - if you install something and it fails... well, you don't want to be in that position.

 

 

Edited June 4, 2020 by Bitpipe

[Mr Punter]

Trench sheets can be hired.  Again I would make this the responsibility o the groundworker to do.

[Adam2]

Thanks for the input- completely agree, it is the people working there that need to decide and be happy with the solution. The sheets will be a bit out of shape hence the intent to purchase - I'm providing materials (at their suggested spec).