Ground Investigation

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At Substruck, we regularly complete ground investigation for restricted access (extensions) and one-off developments all over Ireland. Our multi-purpose Premier Plant Engineering rig can work in many different environments and terrains. The primary type of ground investigation we offer is dynamic probing and windowless soil sampling.

The primary objective of DP is to determine the resistance of soils and soft rocks in situ to the dynamic penetration of a cone. A hammer of a given mass and given height of fall is used to drive the cone. The penetration resistance is defined as the number of blows required to drive the cone over a defined distance. A continuous record is provided with respect to depth, but no samples are recovered.

The requirements for DP, according to IS EN 1997-1 and IS EN 1997-2, are specified in EN ISO 22476-2 Geotechnical Investigation and Testing – Field Testing – Part 2: Dynamic Probing. BS 5930:2015, Charles (2005) and BRE (2003) outline the strengths and limitations of DP. The system is quick, simple, relatively inexpensive and robust which allows a greater number of tests to be carried out in a day. Probes can be carried out close to the foundation outline unlike trial pits.

The primary limitation is that the soil cannot be identified; therefore, Substruck recommends a minimum of one sample for each site. BS 5930:2015 identifies dynamic sampling as a popular method for shallow sampling due to the recovery of a reasonably complete soil profile, a general absence of spoil, the relatively small size and light weight of the equipment which makes for easier access on restricted sites, smaller transport requirements and lower cost. The secondary limitation is where occasional cobbles and boulders are incorrectly interpreted as bedrock, particularly in glacial material. This can be overcome by providing sufficient locations to provide a good representation of the soil profile.

The test results of EN ISO 22476-2 are specially suited for the qualitative determination of a soil profile together with direct investigations (e.g. sampling according to EN ISO 22475-1) or as a relative comparison of other in situ tests. They may also be used for the determination of the strength and deformation properties of soils, generally of the cohesionless type but also possibly in fine-grained soils, through appropriate correlations. The results can also be used to determine the depth to very dense ground layers e.g. to determine the length of piles, and to detect very loose, voided, back-filled or infilled ground. Penetration resistance can give an indication of density index of coarse soil and undrained shear strength of fine soils.

Dynamic probing is distinguished in Table 1 of EN ISO 22476-2 based on the dimensions and masses of the components of the driving device. DPH is selected for general use as giving a good compromise between sensitivity in loose materials and penetration rates in denser materials but there has been far more research completed on DPSH. Please contact us so we can discuss your requirements further and determine the most appropriate approach.