SOIL INVESTIGATION - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 38

initial soil pressure and the (shear) failure pressure can be determined (but initial
pressure is affected by the probe penetration itself).
Monitoring of vertical deformation in the subsoil is possible by an extensometer.
Packer-anchors are fixed (by grout) in a boring, at various levels. A hollow pipe in
the anchor allows transmission of fibreglass rods, which are fixed at other anchors
(maximum 6), allowing vertical deformation recording at various levels. At the
surface, sensors register the displacements of the fibres. Data can be collected
locally or remotely via GSM. An inclinometer is used to measure the horizontal
displacement at different levels. It consists of a plastic pipe, in which the
inclinometer rolls along grooves, while recording deviations of the vertical that are
caused by deformations of the vertical pipe due to horizontal soil movements.
Soil quality survey
Interactions between surface water, groundwater and ground particles are
complex. Consequently, groundwater pollution, sometimes referred to as
groundwater contamination, is not easily classified. In particular, groundwater
aquifers (permeable sand layers) are susceptible to organic (sulphur dioxide,
ammonia, nitrates and phosphates, heavy metals) and inorganic (detergents, food
processing waste, insecticides and herbicides, hydrocarbons, industrial solvents,
cosmetics, medicines) substances from sources that are related to surface water
bodies, heat, industrial spill or ongoing releases of chemical or radionuclide
contaminants or by waste and agricultural fertilizers, which infiltrate into the
subsoil and initiate physical, chemical and/or biological reactions. The pollution
manifests itself as a contaminated plume or floating thin lenses, such as dense
nonaqueous phase liquids (DNAPLs). The movement of the plume, a plume front,
can be part of a geohydrological transport model or groundwater model. Analysis
of ground and groundwater contamination focusses on the soil characteristics, site
geology and the nature of the contaminants. A series of tests for the groundwater
status is defined in the Water Framework Directive (2000/60/EC) and Groundwater
(Daughter-)Directive (2006/118/EC). In situ testing includes boring (sampling for
further lab testing) and specially equipped cone penetrometers, e.g. measuring
volatile substances, electrical resistance, chemical characteristics and a realistic
view by a micro-camera.
Special CPT-probes such as laser-induced fluorescence, X-ray fluorescence, soil
conductivity/resistance, and cameras for capturing video imaging are also
increasingly advanced in conjunction with the CPT probe. The camera probe is a
soil investigation technique that uses a standard soil penetrometer to visualise
record images of the subsoil, retrieved by a lamp, a mirror and the camera itself,
which focuses at the soil aside through a sapphire-glass window of 35 mm 2 . The
camera is connected to a video recorder and a monitor via an electrical signal
cable. Images show the soil at high resolution, clearly exposing grain size and
colour. As images can be magnified up to 100 times on the monitor, the camera
also acts as a microscope, providing information that cannot be seen by the naked
eye.
The water-probe measures the local electric resistance of the pore water in a
small cell with a volume of 5 ml. The ground-probe measures the electrical
resistance of the bulk soil. Combining both results provide information about the