How to Determine Soil Compressive Strength with a Pocket Penetrometer

pocket penetrometer

A pocket penetrometer is a fantastic little invention which geotechnical engineers and technologists find very handy.  It is a small handheld gauge which contains a telescoping rod which can be pushed into the soil. The distance the rod goes into the soil corresponds to a compressive strength on the dial.

Measurement of Soil

The pocket penetrometer measures the compressive strength of the soil.  Most penetrometers available today contain units of tons/ft2 or kg/cm2, and the compressive strength is read directly from the gauge.  Some common conversions are:

1 ton/ft2 = 2000 psf = 13.9 psi

1 kg/cm2 = 98.1 kPa

Limitations

A pocket penetrometer is a primative instrument that is subject to many errors such as non-uniform soil.  As a minimum, you should take a series of measurements in one area and average them.  The penetrometer should not replace laboratory testing or field analysis, or be used to produce foundation design data.

About Bernie Roseke, P.Eng., PMP

Bernie Roseke, P.Eng., PMP, is the president of Roseke Engineering. As a bridge engineer and project manager, he manages projects ranging from small, local bridges to multi-million dollar projects. He is also the technical brains behind ProjectEngineer, the online project management system for engineers. He is a licensed professional engineer, certified project manager, and six sigma black belt. He lives in Lethbridge, Alberta, Canada, with his wife and two kids.

View all posts by Bernie Roseke, P.Eng., PMP

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