9 - Penetrometer Measurements

Abstract

This chapter teaches how to measure mechanical impedance using penetrometer measurements. It first defines a penetrometer and then looks at different kinds of instruments and their uses. It considers the type of tests that are done with penetrometers and what factors affect the measurements, and then looks specifically at the cone penetrometer. A penetrometer is any device forced into the soil to measure resistance to vertical penetration. The earliest soil penetrometers were fists, thumbs, fingernails, pointed sticks, and metal rods. They are still used for qualitative measurements. Two types of tests are done, when making penetration-resistance measurements: a static test and a dynamic test. In a static penetration test, the penetrometer is pushed steadily into the soil. A static penetration test is exemplified by the use of the cone penetrometer, and is discussed in detail in the chapter. In a dynamic penetration test, the penetrometer is driven into the soil by a hammer or falling weight. A dynamic penetration test is done with a spray-tainer or spra-tainer. The spra-tainer is a thin-walled can of 12-ounce size (341 grams) manufactured to dispense products such as shaving cream and bug spray under pressure.