Geotechnical Field Tests

Geotechnical Field Tests

We offer a range geotechnical field tests; which include in-situ shear strength, light weight cone penetration, California Bearing Ratio and Plate Load. Contact us to discuss how this capability can help you.

The Dynamic Cone Penetrometer (DCP) is an instrument that drives a metal cone into the ground by repeatedly striking it with a weight dropped from height. It is designed for the rapid in-situ measurement of ground conditions to allow design of road pavements and other surfaces such as multi use games areas. The simple design means that the DCP is quick and easy to use, portable and suitable for use in locations where access may be difficult.

An 8kg hammer is lifted and dropped through a height of 575mm. The distance pf penetration of the cone tip is then recorded and the cycle repeated. Continuous measurements can be made to a depth of approximately 850mm or when ground conditions permit with extension shafts fitted, to a maximum depth of 2m.

Where strata have different strengths, the boundaries can be identified and the thickness determined. A typical test takes only a few minutes, so the instrument provides a very efficient method of obtaining information which can be correlated to provide an estimate of undrained shear strength (Cu), CBR value, SPT value and other related empirical values useful in geotechnical and pavement design.

The Plate Loading Test (PLT) – a small scale test used to measure the stiffness of the ground beneath the test.  It comprises the controlled loading of the steel plate and the measurement of the settlement caused.  The results can be used to inform bearing pressure of shallow foundations and to determine the appropriate spring stiffness for design of raft foundation or pavement slabs.    It is particularly useful to determine appropriate design values for soils with gravel or larger particle sizes.

Earth Science Partnership’s engineers undertake Plate Load Tests in accordance with BS 1377 Part 9: 1990. The test measures the penetration by applying a vertical load to steel bearing plates. The test can be undertaken using either a 4×4 vehicle or excavator plant as kentledge,dependant on the load or plate diameter that is required.

Plate load 1

In Situ Shear Strength

The California Bearing Ratio (CBR) – a test devised to aid the design of the pavements. Originally that was highway pavements but the test was soon adopted for use of pavements of many types including: concrete slabs for airport and airfield runways and aprons, railway permanent way, temporary roads, working platforms piling platforms, concrete slabs for warehousing etc. and Multi Use Games Areas (MUGA) within schools and sport centres.  The test measures the stiffness of the soil and its provides an indication of its capability to withstand transient loads; i.e. those typically associated with pavements where vehicles load the ground through the pavement for relatively short periods.cbr

The test involves measuring the load required to push a plunger of given diameter, at a defined rate and to a prescribed depth in to the soil subject to the testing.

Earth Science Partnership engineers can measure the CBR of a soil directly via in-situ testing from a 4×4 vehicle, through correlation with Dynamic Cone Penetrometer results and on remoulded samples of soil in the laboratory testing. The results of the testing are used to design an appropriate construction pavement prior to the installation of the surface feature (tarmac/concrete/astro turf etc.).

Contact us to discuss geotechnical field testing on your particular project. For further information see our Geotechnical Engineering capability page.

 

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