Geotechnical work

Site investigations and intrusive ground investigations

Geotechnical work

Intrusive Ground InvestigationsIntroduction:

Geotechnics Ltd have been appointed by United Utilities Water plc to carry out site 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 preferred access routes to the exploratory hole locations together with ground protection

measures and reinstatement prior to the commencement of work.

Intrusive Ground InvestigationsGeotechnics Ltd Saltney Chester have been appointed to carry out site investigation 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