Development and Testing of the Miniaturized Pavement Pressuremeter for Use in Unbound Pavement Layers

BDV 28 977-04A small diameter pressuremeter (SDPMT) was developed, tested and used in numerous correlations at four testing sites on and near the campus of the Florida Institute of Technology. SDPMT probes were inserted directly in to the holes made with the drive pin used during nuclear density testing. SDPMT testing produced lift-off, and limit pressures along with elastic moduli that were all correlated to PENCEL PMT data. SDPMT data was acquired digitally using two types of strain-controlled tests; a conventional incremental volume injection test and a continuous volume injection test. Two probe lengths were developed and tested, one being 6-inches and a second being 12-inches long, to enable either 6- or 12-inch unbound pavement layers to be tested. Data from 159 SDPMT tests were correlated to stiffnesses from 96 Clegg Impact, and 141 Lightweight Deflectometer (LWD) tests, plus 107 dry densities from nuclear density testing. Finite element analyses were conducted so that SDPMT predicted deflections could be compared to LWD measured deflections at all four sites. The SDPMT probes that were developed can be used and repaired much more efficiently than other PMT probes, making them very desirable. The continuous volume injection testing with data acquisition, using the Automated PMT software (APMT) was completed in less than a minute, making it a very useful engineering tool. The correlations showed that both SDPMT stiffness and strength compare well to Clegg and LWD stiffnesses. They also showed a very strong correlation exists between the SDPMT strength and stiffness from the 12-inch SDPMT probe during incremental volume testing. The 12-inch SDPMT tests produced slightly more consistent results than the 6-inch SDPMT tests. The LWD measured and finite element SDPMT predicted deflections were similar, falling within about 10%. In summary, both the incremental and continuous volume injection process for the 6-and 12-inch SDPMT were proven to be useful. These new pressuremeters are recommended for use in conjunction with nuclear density test data to thoroughly categorize the strength-stiffness and density information along any unbound pavement roadway section