Geotechnical work
Site investigations and intrusive
ground investigations
Geotechnical work
Intrusive Ground Investigations
Introduction:
Geotechnics Ltd have been appointed by United Utilities Water plc to carry out site
Intrusive Ground
Investigations
investigation
works as part of a pipeline scheme. This leaflet is designed to illustrate the
type of activity which may be required on your land. We will be happy to agree your
Geotechnics Ltd
Saltney
Chester
have
beenhole
appointed
to carry
out protection
site investigation
preferred
access
routes to the
exploratory
locations together
with ground
measures
and reinstatement
prior to the commencement
of work.
works as part of a pipeline
scheme.
This PowerPoint
is designed
to illustrate the type
of activity which may be required on your land.
Trial Pits
• Trial pits provide a visual
assessment of soils close to
ground surface.
• They tend to be used for a
rapid shallow sampling
programme.
• They can be produced by a
variety of methods from hand
dug pits to machine excavated
trenches.
• Trial pitting is usually carried
out to a maximum depth of
4.5m, depending on soil
conditions.
Window Sampling & Dynamic
Probe Testing
Window sampling is used on sites
where there is restricted access or
where shallow samples are required
without the potential disruption
caused by trial pits.
A Window sampler is a portable
drilling rig.
It can be track mounted or hand held.
Samples are retrieved form a
“window” shell or in plastic tubes
which have been driven into the
ground.
Monitoring instrumentation can also
be installed in the boreholes.
Cable Percussive Borehole
• Cable percussive boreholes are the most common method of site
investigation.
• Used for shallow exploration of soils and soft rock.
• Drilling rigs vary in size and shape and are often modified to suit site
conditions.
• Typically, they are an A-frame from which a steel tube is driven into
the ground by repetitively dropping and lifting it.
• This method of boring permits in-situ testing techniques including
Standard Penetration Testing (SPT),
• Permeability Testing,
• Borehole Vane Testing,
• providing information for geotechnical design.
• Disturbed and undisturbed samples can be retrieved from the
boreholes.
• Monitoring instrumentation can also be installed in the boreholes.
Rotary Drilled Boreholes
Rotary drilling techniques are used for
boreholes in rock.
The equipment may be truck mounted,
track mounted or tractor mounted.
The rig also needs extra equipment
such as a compressor and a water
bowser.
There are two forms of rotary drilling,
open-hole drilling and core drilling.
Open-hole drilling uses a cutting bit to
break down all the material within the
diameter of the hole.
In core drilling, a diamond or tungsten
bit cuts a hole in the rock and an intact
core enters the barrel, which is then
removed as a sample.
Rock cores
Testing for
core for rock
strength to
left.
Selection rock
cores to right.
Storage of
rock cores
bottom right
Installations & Instrumentation
Boreholes also enable the
installation of instrumentation
for the measurement of
various factors.
Instrumentation may include
a) extensometers /
inclinometers for the
measurement of ground
movement;
b) standpipes and piezometers
allowing the monitoring of
ground water and gas
regimes.
Instrumentation and instillation
Standpipes and piezometer
installations maybe be completed
in various ways to suit existing
land use.
Ground protection
• When carrying out works
Geotechnics Ltd try to
minimise any inconvenience
to landowners and
occupiers.
• We try to limit the damage
caused by the plant and
equipment that we use.
• It is possible for us to
arrange for ground
protection track-way and
boards to be laid out along
access routes and at the
site of exploratory holes.
Thanks to Geotechnic, Saltney and
Paul Hayes for the use of images