An Improved Technique for Prebored Pressuremeter Tests

The prebored pressuremeter (PBP) test results depend on the quality of borehole, including its diameter, verticality, effectiveness of cleaning, and degree of wall disturbance. The true elastic modulus cannot be reasonably determined using the cavity pressure-strain curves measured in a borehole of poor quality. In this research, a stainless-steel casing (SSC) was devised to improve the quality of borehole. SSC of 1 to 4 m length was conjugated with a mechanical drilling system (MDS). At a test site, an auger and the MDS with or without the SSC were attempted to drill boreholes for the PBP tests. Among the three techniques, the MDS with SSC produced the reliable values of the initial elastic modulus at a low strain range (0.003% to 0.089%).