Cone penetrometer comparison testing
Wisconsin Highway Research Program
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To build the best, most durable pavement, designers must have accurate information on the quality of the subgrade the pavement will stand upon. Cone penetrometer testing is a promising method for measuring subgrade strength. The equipment is simple and portable, and with it engineers can gather many readings of a subgrade area in a short time. Despite its simplicity, the cone penetrometer requires care to use and equal care in analyzing its data. Wisconsin Department of Transportation (WisDOT) engineers must better understand the strengths and weaknesses of CPT, as well as what it requires in terms of staffing and calibration for field use, and efficient and accurate analysis of the data it yields. This research will compare CPT data to traditional soil boring data at sites with various soils and geology. Data from both methods will be compared, and design assumptions at sites where construction has been finished will also be gathered. Differences in soil and geology data and their design implications will be identified, and CPT limitations and strengths will be noted. Researchers will then suggest situations in which CPT will be useful for WisDOT projects. Ultimately, accurate use of CPT may allow WisDOT to reduce its reliance on more expensive and time-consuming subgrade investigation methods, such as extensive soil boring with drilling equipment. CPT has the potential to be a more sophisticated and less expensive method for subgrade assessment, a procedure that will allow Wisconsin to maximize its budget in building the longest-lasting and smoothest pavements possible.