Geotechnical
Specialists
Bachy Soletanche protects the Englishman’s castle
Bachy Soletanche constructs a slurry
cut-off wall for a Bolton residential development
Leading geotechnical specialist, Bachy Soletanche Limited has
just completed a project for Urban Regen to carry out the
construction of a slurry cut-off wall as part of preparation
works for a new residential development based in Tonge Moor,
Bolton. The purpose of the slurry trench works were to
permanently isolate the proposed built development within the
site - preventing the ingress of any potential contaminants from
the adjoining landfill via both permeable fill and natural
ground.
Andy Tucker, site engineer for Bachy Soletanche commented:
“Due to the depth of the underlying impermeable deposits, and
restrictions of space imposed by the development layout – a
vertical slurry trench cut-off wall was selected as the most
appropriate type of barrier. This environmental measure was
taken to prevent some of the issues raised on the risk
assessment.”
Bachy Soletanche’s process prevents contaminant migration from
outside the site through permeable horizons, which are within
the made ground and the natural superficial deposits underlying
the Northern and Western parts on the site. Andy Tucker
continued:
“One of our considerations was that residents are living in
close proximity to the site – therefore our aim was to ensure
that operations do not affect them”
Works began on site in February to construct the 270metres wall
in clean soils – forming a permanent seal to protect the site.
The depth of the wall varies from 3metres to 13metres and is
constructed using bentonite cement slurry as a support fluid
through the soils.
Andy Tucker added:
“The length of the excavated wall was on an incline which caused
Bachy Soletanche to undertake the work in stepped individual
sections along one part of the length of the wall, each
approximately 10metres long. As a result, we were continually
building bunds to surround the excavation which helps to control
the final slurry levels.”
“As the incline was not originally incorporated into our
designs, we had to re-sequence the excavation method –
eliminating any plans to go over schedule”
Once the slurry mix is installed into the wall, it will harden
in-situ giving a near impermeable barrier to any potential
contaminant. In addition, a width of 1metre will offer the best
cut-off point and future protection for the housing scheme as it
is thicker than typical specified slurry walls. Andy Tucker
commented:
“Normally 600mm is a sufficient thickness, yet the concentration
of possible contamination means this width is preferable.”
When the first sections were constructed and the slurry wall has
taken on a sufficient setting time; the excavation to fill in
the missing sections began. After approximately one week, the
wall is sufficiently set for the excavator to sit above the
previously constructed section of the wall and excavate towards
it.
Andy Tucker concluded:
“The Jethro Street project was completed in early April ready
for the housing scheme to continue apace.”
Email:
fiona@manifestcomms.co.uk