| Why Undertake Ground Investigation? |
A
ground investigation is undertaken at the
start of a project to assess the
condition of the soil, the underlying groundwater
and the geological conditions of
a site.
By it's very nature, a ground investigation
can only sample a very small amount of the
soil, or water on any site. Thus it is
possible that pockets of contamination
and changes in soil conditions lie between
the points tested. This is where the skill
of experienced consultants is needed-minimising
the risks as much as possible.
REC uses a wide range of ground sampling and
analysis techniques in its geotechnical
investigation
work.
A borehole
investigation is an exploratory hole drilled
into the soil and rock to gather
physical data. Both water samples and
gas samples
can be taken out of boreholes. Often
boreholes are left in place after
construction in order to allow continued
gas/groundwater
sampling.
This technique involves using a cable
percussion driven tool to collect samples.
The technique
is especially useful where space is
an issue and is generally used in
the investigation
of softer ground. The technique is
particularly useful because it allows
the maximum
amount of information to be obtained
from the soil sample.
In this type of borehole a rotary auger
collects the sample with a central
core for sample collection built in to
the
drill. This type of boring is particularly
useful when hard ground conditions
are encountered.
When an assessment of the strength of
the rock or when assessing the distribution
of lithologies it is necessary to
retrieve
samples of rock. Rock mechanics requires
the retrieval of undisturbed samples
for physical laboratory testing.
Therefore REC is acutely aware of the
need for
high quality data.
| Trial Pitting
Investigation |
This is a rapid and inexpensive method
of examining the soil on a site. The
process usually involves digging a
trench with an excavator in order to
allow sampling
of the revealed soil. Trial pitting
has its limitations in that soil can
only
be sampled to the reach of the excavator
and the soil obtained is highly disturbed.
Ground Investigation
Services
Borehole Development
|
Rotary Coring
|
Trial Pitting
Investigation
|
Rotary Auger Boring
|
Soil and Groundwater Collection
|
Analysis and Interpretation
|
Soil Vapour Surveys
|
Window Sampling
|
|
Window sampling is a cost
effective technique that is routinely used
to provide an
assessment of ground conditions within
superficial materials. Window sampling
allows for the drilling of boreholes
to a shallow depth (normally <10mbgl),
retrieval of samples (undisturbed and
disturbed) and the installation of
groundwater/ ground-gas pipe work and
infrastructure.
Soil vapour surveys are used
to investigate whether vapours such as
landfill gas,
petroleum hydrocarbons and solvents
are being generated by the soil. These
types
of surveys are usually carried out
on site using direct reading instrumentation,
however REC can, through it’s
UKAS accredited sister laboratory company,
also obtain speciated analyses of vapours
from the soil.
| Soil and Groundwater Collection |
REC collects soil samples
from the ground for chemical analysis to determine the
presence of
any contamination. The method of soil
sampling varies from investigation to
investigation depending on the soil
type, and the contaminants being tested.
Most chemicals can be sampled from
disturbed soil, as would be the case in
trial pitting.
When undisturbed samples are required,
sampling tubes can be used to keep
the soil in its original condition.
Water samples are often collected from
boreholes in the ground and surface water for chemical
analysis. These samples are analysed for
possible contaminants, using knowledge
gained during the investigation about the site’s historic
use.
| Analysis and Interpretation |
The data obtained from the
soil sampling and analysis is used for comparison
with
published values such as the CLEA guidelines.
Expert interpretation of the data then
provides an accurate picture of the conditions.
|
