Our services are divided into Phase 1, Phase 2 and Phase 3 & 4

Site Investigation fieldwork is frequently carried out in the U.K. using a cable percussion drilling rig to obtain engineering information on ground conditions and samples for subsequent laboratory analysis.

Commonly, depths of up to 30-35m can be achieved. As an example only - a 10 to 15 metre deep, 150mm diameter, borehole will normally take 1 day to complete.

In-situ testing and sampling can include Standard Penetration Tests (SPT’s), undisturbed samples (U100’s) along with disturbed, bulk and water samples as necessary.

The precise location of each borehole is often decided on site, in order that boreholes are located to cause least disturbance to other activities in the area and so that services may be avoided. All borehole locations are checked with a Cable Avoidance Tool (CAT).

Cable percussion boreholes are drilled using a Dando 150 cable percussion boring rig, or similar, operated by a two-man crew and all borehole arisings are normally removed from site.

The rig is towed behind a 4-wheel drive Land Rover or similar and is self-contained. During site operations there will be a certain amount of noise from the diesel engine and intermittent noise from the drilling process.Work is normally undertaken under the direction of a qualified geotechnical engineer who may attend during site operations.

When access for a standard cable percussion rig is not available or when the depth of geotechnical information required is 15 metres or less and ground conditions are suitable then the Premier Tracked Rig can be employed.

In-situ penetration testing and sampling can include Standard Penetration Tests (SPT’s), along with disturbed samples as necessary. These can be re-moulded to allow for 38mm triaxial tests to be undertaken.

The SPT comprises a weight of 63.6 kg dropping through a free-fall height of 762mm in accordance with British Standard BS 1377 : Part 9. The weight drives a 50mm diameter “split-spoon” sampler into the ground. The resistance to penetration is recorded for 6 consecutive 75mm increments with the SPT ‘N’ value calculated from an addition of the final four 4 readings.

The rig is brought to site within a large Transit Van and is self-contained and self-erecting. The sampling tube, including a 98mm diameter casing system is driven into the ground with a series of 1 metre long metal tubes. The sampling tubes can be driven through the casing to obtain disturbed samples at regular depth intervals and vary in diameter from 80mm to 35mm.

During site operations there will be a certain amount of noise from the diesel engine and intermittent noise from the drilling process.

The window sampler (also known as the Drive-in-Sampler) is a lightweight portable boring equipment, ideal for shallow boreholes with limited access. 

The drive-in-sampler boring technique can commonly drill down through concrete and brick overburden and superficial made ground  to a depth of 5-7 metres below existing ground level. In ideal conditions depths of up to 10m can be achieved.

The technique is therefore very useful in Subsidence and Contamination sampling situations. An added advantage is that the technique does not arouse as much interest from the general public or create the damage and remedial/reinstatement works that trial pitting does when, for example, excavating through existing tarmac car parks etc.

The drive-in-sampler comprises a series of 1 metre and 2 metre long, 100mm to 35mm diameter, tubes that are driven into the ground using a mini-hydraulic breaker. The tubes are subsequently jacked out of the ground and side windows enable the tubes to be cleaned and small disturbed samples to be taken.

During site operations there will be a certain amount of noise from the hydraulic power pack and breaker unit as the sample tubes are driven into the ground. The precise location of the boreholes is often decided on site, in order that they may be situated so that they cause least disturbance to other activities in the area and that services may be avoided.

Mechanically-Excavated Trial Pits

Trial pitting is often carried out using a JCB type wheeled mechanical excavator complete with a hammer breaker attachment if required.

Work is undertaken under the supervision of a qualified geotechnical or geo-environmental engineer at all times.

No excavations are left unattended when open and once information has been gained from each excavation this is normally backfilled. Where access is restricted, for example rear gardens to residential properties, smaller "mini-excavators" can be employed.

Hand-Excavated Trial Pits

When access does not allow for a JCB or ‘mini-excavator’ Trial Pits can be hand-excavated up to a maximum depth of 1.20m. This will commonly reach underside of foundations and is very useful in sensitive areas where known services are located.

In-situ Shear Vane tests can be performed in open Trial Pits in order to provide quick shear strength results of soil. It is not recommended, for the purposes of foundation design, that Shear Vane values replace those from conventional triaxial tests.

The Dynamic Probe operated by Risk Management Limited is classed as a Dynamic Probe “Heavy” (DPH) in accordance with BS 5930:2015 “Code of Practice for Site Investigations”.

The Dynamic Probe is hinged for easy transport and access to site.

Height when extended: 2.34m Width: 0.78m Length: 0.785m Total weight approx: 360 kg

The Dynamic Probe uses the 50 kg weight dropped in “free-fall” from a fixed height of 500mm to drive a 15cm2 cone into the ground.

The number of blows per 100mm is recorded and the resulting blow counts can be used to obtain equivalent Standard Penetration Test (SPT) ‘N’ values.

Approximate ‘Equivalent’ SPT ‘N’ Values can be determined by dividing the cumulative blow counts for each 300m of penetration by 1.5 as recommended by Card and Roche. The results are presented as plots of blow counts versus depth.

During site operations there will be noise from the continuous blows to the top of the drive rods.

On completion of a borehole, gas and groundwater monitoring installations can be installed comprising 50mm or 19mm diameter (depending on plant used) HDPE slotted and plain casing as necessary wrapped in a geotextile sock to prevent silting up and finished at ground surface with a lockable stopcock cover, concreted in flush with the existing ground surface.

A cement/bentonite seal is normally installed from 1.00m to ground level and the installation finished with a gas valve on top of the pipe and a lockable stopcock cover concreted in flush with ground level.

Gas monitoring of carbon-dioxide, methane, oxygen and flow levels can be recorded and together will provide a Gas Screening Value (GSV) and a classification in accordance with CIRIA Publication C665 “Assessing Risks Posed by Hazardous Gases to Buildings (Revised 2007)” and/or the NHBC “Traffic Light” System.