Cable Percussion drilling is one of the most common methods of site investigation. Boreholes can be drilled to depths of up to 60m at a variety of diameters ranging from 150mm to 300mm. The boreholes are advanced using a variety of cutting tools that retrieve soil samples. This is carried out whilst simultaneously installing the temporary casing into the borehole. The casing then prevents any loose soils collapsing into the borehole.
As the borehole is advanced in-situ testing can be undertaken including Standard Penetration Testing (SPT), borehole vane testing & permeability testing.
Drillers take both disturbed and undisturbed samples from the borehole. Experienced geo-environmental engineers log the samples which in turn can be sent off for laboratory testing.
When completed, monitoring equipment can be installed directly into the boreholes. This allows ongoing measurements to be taken by dedicated technicians, which can include gas and groundwater monitoring.
Strata’s cable percussive drilling crews are directly employed and are NVQ qualified in land drilling and British Drilling Association (BDA) audited to ensure high standards in both safety and quality.
The crews are supported by our qualified geotechnical engineers who undertake supervisory and technical duties.
Strata Geotechnics can provide difficult access and ground protection solutions for our standard Cable Percussion rigs and offer our unique VETRAK rig for restricted access sites.
In conjunction with our inhouse rotary drilling crews we can advance the boreholes into bedrock through the base of the cable percussion boreholes and recover rock core samples.
The VETRAK uses the same drilling principal as a traditional CP rig. However it is mounted on a self-contained tracked machine. This specialist rig is able to access through a 800mm wide doorway, and can also have a shortened mast to enable drilling beneath a 4m height restriction.
The rig is transported to site by lorry or trailer and is easily and safely erected on site with a hydraulically operated mast. The hydraulic winch is fully enclosed with emergency stop buttons in easy reach of both the lead driller and the assistant driller.
The alternative restricted access rig has always been the Dynamic Sampler (DS), which is also mounted on tracks. The DS rig is restricted to depths of typically 10metres and is not able to ‘chisel’ through hard stratum. The VETRAK rig has the access capability of a Dynamic Sampler but the drilling capability of a Cable Percussion Rig.
Cable Percussion is a tried and tested technique for drilling through superficial deposits and very weak rocks. The borehole is advanced by using a cutting tool which is dropped down the hole to retrieve the soils. All whilst advancing a casing to prevent the borehole collapsing. The drilling method allows accurate definition of strata boundaries and soil type together with insitu soil strength testing (SPT) and Class 1 sampling for subsequent laboratory testing.
To progress boreholes to depths of up to 35m the casing diameters can be reduced as the borehole is advanced. This allows the opportunity to introduce bentonite seals to prevent a migration pathway for contaminants. Various monitoring wells and geotechnical instrumentation can be installed within the VETRAK CP boreholes.
The VETRAK rig is ideal for working on restricted access sites such as rail projects, inside buildings, at the rear of domestic properties or under service station canopies. It has also been used for tracking along footpaths where minimal disruption is required and is easily lifted into the work site using a crane.