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T&D > Programs Areas > Inventory & Monitoring > Williamson Drive Probe Program Areas
Williamson Drive Probe
Mike Mitchell, Project Leader

A project proposal was made for improvements to the Williamson Drive Probe (WDP). The proposal called for minimizing human error associated with using the WDP and the ability to correlate the data collected using the WDP to the Standard Penetration Test (SPT). To accomplish these requirements, the couplings and test points associated with the WDP are to be analyzed. The couplings are used to connect two consecutive pieces of pipe together and a pipe plug on the end of the WDP is referred to as the test point. Also to be analyzed is the hammer weight, how the hammer is dropped and to develop a device which efficiently transfers energy from the falling hammer to the ground. Along with these improvements, the WDP cost is to be kept to a minimum allowing for a cheap and accurate alternative to other test equipment available.


It was first developed by Douglas Williamson, a USDA Forest Service Geotechnical Engineer. He developed the WDP as a cheap alternative for determining soil relative density. The principle behind the WDP is to use an 11lb hammer dropped from a vertical distance of 39 inches. The impact from the hammer drives sections of pipe into the ground. A correlation between the blows required to drive the WDP into the ground 6 inches is then used to determine ground conditions. The WDP is also used to detect ground water using small holes drilled in the pipe which is inserted into the ground. With these many uses and the low cost, (under $500) the WDP is an effective alternative to other tests which require expensive equipment and are less portable.

Additional Information