Dando Terrier probing rig working on site
Dynamic Sampling:
Dynamic Sampling is a technique of site investigation most suited to shallow soil sampling.
Dynamic sampling (windowless sampling) is a commonly used method of putting down boreholes using a compact tracked light percussion boring rig. OCB Geotechnical operate a Dando Terrier rig that is transported to site in an enclosed van.
Dynamic Probing:
Dynamic probing is a commonly used rudimentary method of assessing ground conditions by measuring resistance against penetration of a cone being driven over fixed intervals.
OCB Geotechnical operate a Dando Terrier rig that is transported to site in an enclosed van.
The method involves driving a solid cone into the ground, using repeated blows of a hammer of fixed mass falling through a fixed distance. The hammer strikes an anvil which is rigidly fixed to rods which are of a smaller diameter to the cone, and transmit the hammer energy to it. As the cone is driven into the ground, the number of hammer blows required to drive it through each increment (typically 100 mm) is recorded. The blow count is plotted against depth to provide a continuous profile of penetration resistance against depth.
Heavy Dynamic Probing (DPH) involves the use of a cone 43.7 mm in diameter, driven by a weight of 50 kg falling through 500 mm. Super Heavy Dynamic Probing (DPSH) involves the use of a cone 50.5mm diameter driven by a weight of 63.5 kg falling through 760 mm.
Dynamic Cone Penetration Test:
The TRL Dynamic Cone Penetrometer (DCP) is a widely used in-situ test for providing an indirect measurement of the California Bearing Ratio (CBR) value, as applied in pavement design.
The equipment was developed in conjunction with the UK Transport Research Laboratory, is used widely throughout the world, and is referred to in the UK Highway Agency Interim Advice Note 73/06.
The penetration per blow (the ‘penetration rate’) is recorded as the cone is driven into the ground and then used to calculate the strength of the material through which it is passing.
A change in the penetration rate indicates a change in strength between materials, thus allowing layers to be identified and the thickness and strength of each to be determined. These layers are then grouped together into the pavement layers of base, sub-base and subgrade, supplemented by test pit or as-built records if available.