GEOTECHNICAL INSTRUMENTATION AND MONITORING

Causeway Geotech Ltd have the capability to install and subsequently monitor a wide range of geotechnical and geo-environmental instrumentation. These can be for a variety of applications, such as groundwater and ground gas monitoring, and ground movement – to name but a few.

We are able to install a full range of groundwater and gas monitoring instruments, including standard standpipe piezometers set in sand cells within boreholes, and slotted standpipes typically from 19mm up to 50mm internal diameter, although alternative sizes are also available.  Multilevel monitoring and sampling installations may also be provided, where several discrete levels of interest may be monitored from a single borehole. Groundwater levels are measured using a graduated dipmeter and ground gases monitored using an infra-red analyser. Multiphase dip meters are employed on sites where there is potential free product within the water column.

If long term groundwater information, or for example, the variation in water level over a series of tidal cycles, is required, we carry a large stock of pre-programmable electronic data-loggers which are installed in the piezometers/standpipes to record continuous data. These are later collected and the data downloaded and presented in AGS format.

When measuring gas concentrations, both initial and steady state levels are recorded together with atmospheric and installation pressure and flow rate – all in accordance with the CIRIA guidance.  Where long term continuous gas monitoring is called for, we have strong relationships with a key supplier for wellhead monitoring devices that record ground gas and flow rate on a continuous basis. This device can be accessed remotely via an online portal allowing the Client to assess the data in real time.

In addition to conventional groundwater piezometers, vibrating wire piezometers may be installed.  These are particularly useful where monitoring of piezometric levels in low permeability soils are required.  The instruments are grouted into the boreholes and may either be monitored manually at discrete times, or by using automated data recorders which can record the piezometric data at prescribed intervals over days, weeks, or even months. We carry a range of dataloggers and standard industry software which is used to process the data in AGS format.

With regard to ground movement, one of the simplest techniques is installing and monitoring the level of settlement plates set into the ground.  More sophisticated monitoring of ground movements includes the use of extensometers, with target magnets placed at multiple levels in boreholes, and borehole inclinometers (used to assess lateral movements), commonly used in slope stability analysis, which are monitored using a biaxial probe. Causeway Geotech have the capabilities to both install such instrumentation, as well as provide the professional services for monitoring and interpretation of the data produced thereafter. We have experience of installing such instrumentation to depths of 120m below ground level to determine possible settlement of ground associated with disused solution mine workings.