Site Investigation
There are many facets to drilling and the most applicable to site investigation is cable percussive, windowless sampling and rotary drilling.
Rotary Core Drilling: This drilling technique is subdivided into rotary percussive and rotary coring. They are both employed where penetration is required through very dense or very stiff soils, or into bedrock.
Where Rotary Coring is undertaken, we have a vast range of systems to suit your requirements, from conventional core barrels of various diameters to wireline systems such as Geobor S where samples are recovered in seamless plastic tubes.
Our Beretta T44 drilling rig is capable of obtaining continuous insitu tests and samples of soils using dynamic sampling equipment as well as carry out the Standard Penetration Test (SPT). We can also carry out conventional coring using different-sized barrels to facilitate pressuremeter tests.
At MT Geoservices Ltd, we have a low ground bearing compressor-mounted JCB Fastrac and low loader, which gives us and our clients a unique advantage when working in rural farmlands or mountainous wind farm locations. This eliminates having to rely on farmers or third-party companies for movements across sites.
We can also carry out Lugeon/Packer Tests to check and record the hydraulic conductivity of rocks and issue a calculated result suitable for use in your design work.
The Rotary Percussion system available to us are Symmetrix, Robit and Odex; these allow full-hole drilling and casing through unstable ground.
Open Hole Drilling: The choice of open-hole drilling is dependent on the requirements of the investigation. This method offers a quick way of investigating into voids relating to issues such as karst topography or investigation of old mine workings (Coal Mining Risk Assessment). It can also be used to get a rough estimation of strata changes by interpreting drilling parameters and lastly for Dewatering. This method does not offer a core sample and geological interpretation is fraught with many difficulties however it allows for drilling of more boreholes in a short time period. We offer direct or reverse circulation systems with varied sizes of conventional tricone or drag bits and down-the-hole hammer techniques using air, water, mist, polymer or foam circulation.
Geo-Environmental Drilling: This is a low-cost drilling method for shallow geotechnical and geo-environmental sampling, generally suitable for cohesive strata and sands, where information on shallow ground conditions are required or shallow foundations are expected to be feasible.
It is usually carried out by a lightweight, compact easy to manoeuvre rubber-tracked drilling rig with minimal ground disturbance making it ideal for sites with narrow access, and sensitive environmental policy. The rig can be tracked up slopes and driven through a standard domestic doorway. In areas where there is low-headroom or access limitations, hand-held equipment can be used.
The percussive window or windowless sampling method involves driving cylindrical steel tubes into the ground using a hydraulic hammer. The sampler uses one-metre long extension rods and is driven into the ground by a percussion method using a drop hammer, obtaining one-metre-long plastic-lined samples to a depth of up to 10m in favourable geology (generally 6m), hence providing a full soil profile. Standard Penetration Tests (SPT), U100 and UT100 samples can be obtained with this technique.
We can also attach rotary concrete coring head to our rigs to enable us to penetrate hardstanding grounds, where necessary.
Our terrier rig is also capable of carrying out Dynamic probing, which is another method of soil profiling. This involves driving a sacrificial cylindrical cone into the ground with a 63.5kg rammer, dropped through 750mm and the penetration rate is determined by the number of blows over a distance of 100mm.
As well as being an effective and low-cost method of getting the estimated soil strength, this method is also good for determining depth to suitable ground conditions for your foundations, to prove depth to rockhead where it varies across a site, investigating cavities and dissolution features.
Dando Terrier Rig