UKTC Archive


Subject: RE: APN1
From: Mark Wadey
Date: Dec 12 2000 15:56:03

As I understand it APN1  does not work for several reasons

*       The area for installation usually has to be pre-rutted
*       Poor use of aggregate fill such as Type 1 Roadstone can lead to
toxic leaching. (I'm not 100% sure, but I think it is down to the lime
content and amount of small fines)
*       Once the aggregate fill has been placed on to the Geogrid, the
material must be rolled and compressed to enable sufficient tensile strength
for load spreading, hence pre compaction of the soil.
*       Side butting wooden boards do not always hold firm a hard surface
when put under heavy loading from large vehicles.
*       If surfaces are installed below a driveway and need repair in the
future, there is no way to reinstate the drive again without damaging the

There are alternative products (Geoweb) that can be found from companies
such as Cooper Clarke, however it must be stressed that, as we all know,
sites and conditions surrounding the trees will always vary. A great deal of
thought should go into how such a build above existing soil levels will be
successfully achieved without realistically compromising the root systems.


From:         Dealga O'Callaghan[]
Reply To:     UK Tree Care
Sent:         12 December 2000 06:52
To:   UK Tree Care
Subject:      RE: APN1


You are right - geogrid is not adequate.
I would suggest that you look at Geoblock
which I have used many times with success.
It sounds similar to Volta Cell.

Remember, the only aspect of APN1 that is worth anything
is the fact that it establishes the principle that surfaces
can be constructed over roots without damage.  Everything else
is, as you say, theoretical - by their own admission, the AAIS
never built nor tested the construction shown in APN1.  They never
'Practised' it!!

Interesting what?


-----Original Message-----
From: []On Behalf Of
Sent: 11 December 2000 23:04
To: UK Tree Care
Subject: Re: APN1

I am in the process of using APN1 to guide us thro the specification for a
small car park under some protected trees in a protected setting.

The Geogrid refered to in APN1 seems a bit theoretical. So far research
produced a product called a VOLTA CELL, confinement system which is
in panels and can be secured by pins. I am acquiring a sample.

Does anybody have any experience of the same product or any other
alternatives or any info on the weight distrubution it will afford over
tree roots.


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