Falling Head Test

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Definition - What does Falling Head Test mean?

A falling head test is one of the variable head test procedures that is undertaken in-situ in a borehole to determine the permeability of the soil. The falling head test is carried out for permeable soils and requires knowledge of the groundwater level in the area.

It is an important part of the geotechnical investigation in trenchless technology for the design and installation of pipelines and determining the route for boreholes.

Trenchlesspedia explains Falling Head Test

Permeability gives a measure of the soil's ability to allow water to flow through the pores. For carrying out the falling head test first the depth is measured from the top of the standpipe to bottom of the well. A slug is rapidly lowered into the well causing a sudden rise in the water level. The recovering water level is measured until it is fully recovered.

This test carried out in-situ gives more reliable results than when conducted in the laboratory. Boreholes to carry out the test can be drilled using cable percussion boring using which boreholes up to a depth of 60 meters can be drilled.

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