Soil Investigation


The investigation of the geology and previous uses of any site, together with the determination of its engineering, environmental and contamination characteristics is fundamental to both safe and economic development.

GEONAMICS is a specialist company that can provide guidance and management of the investigation process through all phases of study, ground investigation, testing and design. Methods range from non-intrusive geophysics through to fully intrusive borehole installations. The method depends on parameters such as depth, soil type and access to the site It is common for investigations to be phased – allowing the results of the early phases to guide the next stages.

Soil Investigation Techniques that are employed for the majority of projects as followed :

  • Boreholes
  • In-situ Testing
  • Trial Pitting
  • Dynamics Probe Testing

BOREHOLES

Rotary Drilled Borehole

Rotary drilling techniques are employed where boreholes are required into soil or bedrock. This utilises a rotary drilling to advance a hole into the ground. Soil samples are collected from a core device from the centre of the drill stem. The choice of drilling equipment depends on ground conditions. Equipment varies from a relatively compact (2m x 1m x 2m high) self powered rig. Rotary drilling is particularly useful in difficult ground conditions or when rock coring is required.

Rotary drilling borehole are used on land and on coastal areas.

Cable Percussive Borehole

The minimum diameter of hand auger boring is 100mm and casing not be required. It was advanced by hand auger tool, Hand Augers may be used for any proposed where disturbed sample are satisfactory and are valuable in advancing holes to a depth at which disturbed sampling are required.

 

Hand Augering Borehole

A large (4m x 4m x 7m high) percussion rig that drives a cutting or collecting instrument (dependent on ground conditions) into the ground, to collect soil that is then removed and sampled. This can be a slow technique; however the advantage is that the hole can be cased to prevent collapse in loose soil layers, allowing easy installation of groundwater sampling pipework. It is highly adaptable to, and designed for, geotechnical testing.

IN-SITU TESTING

In-situ testing techniques including Standard Penetration Testing, Permeability Testing, Borehole Vane Testing, Pressuremeter Testing and Packer Testing can all be carried out in the boreholes in order to provide information for geotechnical design. Disturbed and undisturbed samples are retrieved from the boreholes for inspection and logging by engineers and subsequent testing in our laboratories.


TRIAL PITTING

Trial pitting can be carried out by a variety of methods from hand dug pits to machine excavated trenches. Trial pitting is generally carried out to a maximum depth of 4.5m with standard excavation plant and, depending on soil conditions, is generally suitable for most low rise developments. All trial pit investigations are supervised by experienced engineers with a thorough understanding of geology and soil mechanics.

Cone Penetration

DYNAMICS PROBE TESTING

Cone Penetration Test

To carried out the cone penetration test is pushed into a soil deposit while various measured parameters are recorded. The test is similar to the Dutch Deep sounding (or piezocone test) with the addition of a cone penetration element in the probe to measure water pressure. The test is also known as pore pressure sounding or CPTU.

 Mackintosh/JKR Probe Test

MackintoshThis is a dynamic penetrometer test used to check the consistency of the subsoil. Mackintosh Probe which has 30° cone penetrometer while JKR Probes has 60° cone penetrometer. This is a light dynamic test and the cone is driven directly into the soil by driving a hammer 5 kg. weight dropping through a free height of 280mm. The probe is unable to penetrate into medium strength soil and gravelly ground.