Bachy Soletanche Ltd - Preparation is the Key for Bachy
Soletanche at Must Farm
Leading geotechnical specialist,
Bachy Soletanche Limited (BSL) has recently completed
the construction of an 1825metre slurry cut-off wall at
Must Farm in Cambridgeshire – preparing the site for
future quarrying of Oxford Clay and any present sands
and gravels. In a contract worth around £800,000, BSL
has overseen all environmental works as the project’s
main contractor.
The Must Farm site, near Whittlesey, Peterborough is to
be developed by Hanson Building Products as a quarry to
extract brick clay, sand and gravel, to be transferred
to its Kings Dyke and Saxon Brick factories. However,
before quarrying works can begin, migration measures
have to be carried out by BSL to prevent the ingress of
groundwater from Kings Dyke to within the Must Farm
boundary, which in turn will protect the groundwater
levels of the Nene Washes.
Barrie Arkwright, Contract Manager at Bachy Soletanche
commented:
“Must Farm has several links to groundwater networks,
such as an existing flooded quarry located in the
Western part of the site and also the Kings Dyke. As a
result, Hanson Building Products required the
construction of a slurry cut-off wall to stop the water
from the Kings Dyke migrating through the sands and
gravels – whilst preventing the external groundwater
levels from lowering – as the site is quarried.”
The Kings Dyke tributaries also cross the site in five
places, as Barrie Arkwright explained:
“We had to create a temporary causeway across each of
the five ditches by laying casings lengthways into the
water. This created a makeshift bridge for the plant
equipment to drive over, and for the excavator to stand
on when excavating the slurry trench.”
In order to create the slurry cut-off wall, a trench had
to be installed using two excavators that work
simultaneously. As these continue along the wall, the
slurry, which is a carefully selected mix of bentonite,
cementitious materials and water, is pumped into the
trench utilising two mixer plants. Barrie Arkwright
continued:
“Our supply of slurry had to remain constant due to the
vast 1.8kilometre distance between the trench and the
slurry plant. This required the two mixers to have
enough pressure to pump the slurry through approximately
2000 metres of pipeline in order to reach the trench. Up
to 450m3 of slurry can be mixed and pumped daily to
produce approximately 50 linear metres of wall.”
“Once the trench is excavated and filled with the slurry
mix, it will set to provide a low permeable barrier.” He
added.
The land at Must Farm is occupied by tenant farmers and
as the farmers will return to crop the land after BSL
completes the migration measures – further preparation
works were required to protect the farming land around
the site. Barrie Arkwright explained:
“A 25metre strip of vegetation and topsoil needed to be
stripped down to a depth of 300 millimetres. This would
stop any of the slurry arising contaminating the topsoil
and allow them to continue farming once the slurry wall
is capped with clay and the topsoil replaced. The Oxford
clay used to cap the wall is quarried from the old Must
Farm quarry on the site. As the wall runs right through
the steep banks of the now depleted lake, the steep
banks have had to be built up to create a level platform
that will enable excavation of the wall once the Oxford
Clay has been quarried.”
“The excavated soil will remain on site and then
replaced when the slurry wall is finally complete.” He
added.
The slurry wall is to be constructed along sections of
the southern and western areas of the quarry boundary
and will stretch to a total length of 1825 metres. The
longer section is 1600metres, and the shorter section,
on the far side of the flooded quarry is 225 metres. The
depth of the wall varies between 6metres and 10.5metres
deep and has to be installed 1.5 metres into the Oxford
Clay to ensure it is watertight.
The slurry cut-off wall was completed at the end of
June. The works will allow the area around the Must Farm
site to be dewatered, enabling excavation of the upper
superficial deposits.
Email:
fiona@manifestcomms.co.uk
Arundel Jones Associates Ltd
Hill Farm, Linton Hill, Maidstone, Kent ME17 4AL
Tel : 01622 745333
news@buildingdesign.co.uk
Registered in England and Wales No. 07334149
News Categories : Geotechnical Specialists
Piling
Structural Retaining Walls
Ground Anchors Soil Nailers
Jet Groating Injection Grouting
Environmental Engineering
Building Design Engineers
Civil Engineering Projects
|
Geotechnical
Specialists
