Land Services
Ground Investigation
What is Ground Investigation?
Ground investigation is the process of exploring the geotechnical and environmental properties of the ground, including groundwater.
The main purpose of ground investigation is to reduce and control ground-related risks in construction.
Ground investigation should be considered the first step of any development process thus enabling appropriate consideration in the design stages of a project.
Causeway Geotech employ a wide range of ground investigation techniques, find out about some of them below.
Rotary Drilling
Rotary Drilling
Rotary drilling techniques are employed where penetration is required through very dense or very stiff soils, or into bedrock. Standard methods employed may be subdivided into rotary percussive and rotary coring. We operate a broad range of tooling using a varied fleet of rigs and we are confident we can provide the perfect solution for your site. Our rigs range from the compact multi-purpose tracked Comacchio 205s, through larger track and lorry mounted Comacchio 601/602 and T7 units.
Sonic Drilling
Sonic Drilling
Sonic drilling is an advanced drilling technique which operates on the principle of high frequency vibratory energy generated inside a sonic head to advance a core barrel downwards through a substrate. Production rates are typically significantly quicker, and sample return and quality often much higher, than other drilling methods. The system has also been proven to be the optimal method for drilling through challenging ground conditions where old technologies struggle, such as dense granular materials, heavy made ground and landfill material.
All our sonic rigs are dual purpose allowing for sonic methods in the overburden followed by rotary coring follow-on in suitable soils and rock. This ensures full recovery from ground level to the base of the borehole with a single rig set-up.
Cable Percussion Boring
Cable Percussion Boring
Cable percussion boring returns information on soils to depth. Complementary in-situ testing techniques include Standard Penetration Testing, Permeability Testing and Borehole Vane Testing. Disturbed and undisturbed soil samples (including Piston Samples) are retrieved for environmental and geotechnical testing in our laboratories.
Causeway Geotech has several Dando 2000, 2500 and 3000 cable percussion rigs within our fleet. In addition to this, we have bespoke low ground bearing units comprising specially adapted cable percussion rigs mounted on low ground bearing wide-tracked vehicles to allow access over soft and challenging ground terrain.
Dynamic Sampling
Dynamic Sampling
A method of investigation best suited to shallow soils sampling and commonly employed in environmental investigations, dynamic sampling is carried out by either tracked light percussion rigs or hand-held (Carl Hamm) samplers. Samples are retrieved in seamless plastic tubes for logging by a suitably qualified engineer. Window(less) sampling is particularly suited to restricted access sites, contamination investigations, and where disturbance must be kept to a minimum. The track mounted equipment is also capable of carrying out dynamic probe testing. This is a continuous soil test procedure which enables the relative density or strength of the ground to be assessed to depths of 10m or more.
We operate a fleet of Dando Terrier light percussion boring rigs that are easily and efficiently deployed to sites. Coupled with this, for rougher terrain or steep slope access, we have bespoke track dumper-mounted Dando Terrier rigs. For mid-slope and embankment works, as well as works on railways, we have specially adapted rigs which mount directly to quick hitch fittings of excavators/RRVs.
In-Situ Testing
In-Situ Testing
We offer a broad range of in-situ testing, carried out by a team of skilled and trained Site Technicians and Engineers.
In-house services include:
- DYNAMIC CONE PENETROMETER: UKAS-accredited testing. Used as an initial estimate of California Bearing Ratio (CBR) for road design.
- IN-SITU THERMAL RESISTIVITY: Thermal resistivity measures the capacity of the soil to conduct or dissipate heat, used primarily in data centre and cable route works. Can be carried out in trial pits, slit trenches or on borehole samples.
- IN-SITU SOIL RESISTIVITY: Soil resistivity testing determines the conductivity of the soil and semi-directly relates to the amount of corrosion activity you may have on a buried structure. Measured using the Wenner 4-Pin Method.
- MACKINTOSH/PEAT PROBING: Enables a quick and accurate determination of the depth of peat deposits.
- FIELD SHEAR VANE: The shear vane test is quick method of measuring the undrained shear strength of low strength cohesive soil in the field.
- PLATE LOAD TESTING: UKAS-accredited testing using the PLATEMAN system which presents results in real-time displayed on a rugged PDA. Used as a final verification of subbase layers for the construction of roads, pavements, piling mats and crane pads. Also used as a formation level test for some structures such as retaining walls.
- SOAKAWAY, INFILTRATION, PERCOLATION TESTS: Tests which investigate the hydrogeological characteristics of the soil to aid in the design of drainage systems. Carried out in machine or hand dug pits at ground level.
- VARIABLE AND CONSTANT HEAD PERMEABILITY TESTING: Tests done in boreholes or standpipe installations to determine the permeability of soil or rock at depth.
- PACKER (LUGEON) TESTING: Tests undertaken in boreholes to determine the hydraulic properties of bedrock at discrete horizons.
- CLEGG HAMMER TESTING: Provides an estimate of California Bearing Ratio (CBR) at ground level, e.g., where site levels have already been reduced to formation level.
Trial Pitting & Slit Trenching
Trial Pitting & Slit Trenching
Trial pitting is used as a quick and cost-effective method for gleaning a basic understanding of the soil profile across a site, or to supplement information provided by other methods of investigation that are completed concurrently.
Additional testing in trial pits can include infiltration/soakaway testing (in accordance with the guidance as set out in BRE 365), CBR testing and in-situ strength testing.
Cone Penetration Testing
Cone Penetration Testing
Cone Penetration Tests (CPTs) are carried out using a sonic or rotary rig equipped with Drill’n CPT module, or using traditional standalone CPT rigs.
The advantage of our Drill’n CPT module is that with a single set-up, we can alternate between CPTs and sonic/rotary drilling. We can drill through obstructions, such as cobbles and boulders, a particular problem in ground and glacial soils, before reverting to CPT. This allows for a high quality, continuous profile of the ground without data gaps.
Ground Water/Ground Gas Monitoring & Sampling
Ground Water/Ground Gas Monitoring & Sampling
Causeway Geotech installs a variety of groundwater and gas monitoring instruments in a range of sizes. 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.
We offer the option to undertake low flow groundwater sampling with groundwater chemistry measurement. This method of sampling provides more representative groundwater samples as it extracts the groundwater at rates comparable to ambient groundwater flow and reduces potential for the mixing of stagnant water with water from the well response zone. This method also allows measurement of groundwater chemistry (pH, D.O., redox, conductivity, temperature) and turbidity of the purged water before a sample is taken.
Analysis of groundwater samples can be arranged through our laboratory. The results of monitoring and testing often forms a crucial part of Environmental Assessments.
Pre-programmable electronic data-loggers are employed where long term monitoring is required, or where continuous measurements are required for pump tests or tidal cycles. Vibrating wire piezometers may be installed where monitoring of piezometric levels in low permeability soils are required.
Where long term continuous gas monitoring is called for, wellhead monitoring devices can be installed to record ground gas and flow rate on a continuous basis. This device can be accessed remotely via an online portal allowing the Client to view the data in real time.
Ground Movement Monitoring
Ground Movement Monitoring
Monitoring of ground movement includes simple techniques such as settlement plates and datum rods. More sophisticated monitoring of ground movements can involve 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. Our experience includes installation of instruments to depths in excess of 100m to determine settlement of ground associated with disused solution mine workings.
As well as the installation and monitoring of instruments, we can offer interpretation and recommendations through our Geotechnical Design department.
