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As part of its comprehensive range of site investigation services the Harrison Group is able to carry out a range of in-situ testing and sampling. We are able to make use of a range of in-house resources including: -
- Tracked and wheel mounted dynamic probes
- Tracked, wheeled or hand held window sampling equipment
- California Bearing Ratio (CBR) equipment
- Plate Bearing Testing (PBT) equipment
- Nuclear Density Gauges (NDG)
The range of tests available includes, but are not restricted to, the following: -
- California Bearing Ratio testing (CBR) - this is a penetration test for evaluation of the mechanical strength of road subgrades and is carried out on site. A load is applied to a standard plunger which penetrates a soil sample in order to determine the resistance to deformation under load. As the load is increased, regular readings are taken of load applied against penetration of the plunger. The results give the CBR value for the soil and allow the road pavement to be designed.
- Plate Bearing Testing (PBT) - to determine settlement and for calculation of Modulus of Sub-grade Reaction.
- Sand Replacement Density testing (SRD) – to determine the dry density of in-situ soils.
- Nuclear Density Gauge testing (NDG) – to establish the moisture content, wet density and dry density of soils. This test is carried out on site and used to establish the wet & dry densities and moisture content of soils and granular construction materials. Measurement of soil density in situ is most commonly used to assess whether material used as backfill, lining or capping (road and landfill construction for instance) has been adequately compacted.
The site operation is non-destructive, with results immediately available, resulting in minimal downtime for the contractor. As this method makes use of low level radiation, site personnel are fully trained and strict health, safety and environmental procedures strictly adhered to. - Permeability testing – falling/rising and constant head tests in boreholes.
- Soakaway testing – to establish soakage rates in boreholes and trial pits.
- Shear vane testing – used to measure the undrained shear strength of cohesive soils.
- Penetration Testing (DPT) – Penetration testing is used to provide a rapid assessment of sub-surface stratigraphy and relative density either by dynamic or static cone methods: -
- Dynamic Penetration Testing (DPT) is carried out by means of a wheeled or track mounted percussion hammer; measurements of blow counts are taken to obtain a continuous profile of the relative density of the ground penetrated. Soil samples are not usually obtained using this method and so penetration testing is often carried out in conjunction with other investigation methods such as boreholes in order to provide infill information, or where obstructions or the presence of voids is suspected. Depending on the nature of sub soils, probing can be carried out to a maximum depth of about 20m, with up to 100 linear metres of testing achievable in one day.
- Static Cone Penetration Testing (CPT) involves hydraulically pushing (rather then hammering) a cone into the ground at a constant rate of penetration. During penetration, electrical measurements are made of the cone resistance, the side friction and in a piezocone test, the pore water pressure generated, to provide a detailed picture of the variation of the measured parameters with depth. Analysis of the data can provide information on the sub-surface stratigraphy and estimates of various useful geotechnical parameters. A number of different cones are available including those able to measure hydrocarbons, gamma rays, electrical conductivity, detect hydrocarbons and magnetometers for the detection of buried UXO. The technique causes minimal soil disturbance and productivity is high with up to 150m a day being achievable in suitable soils.
- Pile integrity and load testing – Non Destructive Testing (NDT) and static or dynamic load testing of piles.
- Structural monitoring – using a variety of instruments ranging from basic “Tell Tales” to sophisticated digital extensometers and load cells.
- Window Sampling is a site investigation method that utilises portable equipment to drill small diameter boreholes in order to take soil samples and install monitoring wells. Drilling equipment is portable and versatile: -
- Track or wheel mounted, which make use of a percussion hammer to drive the sampler tubes.
- Hand held, which makes use of a breaker attachment to drive the sampler tubes.