Interpretation of pressuremeter tests using a curve fitting technique.

摘要

Interpretation of pressuremeter tests is the main subject of this study. For in situ tests, the interpretation of results to yield soil parameters can be very difficult and decisive for their acceptance by the geotechnical engineering community. Fortunately, the pressuremeter test is one of the few geotechnical in situ tests that has well defined boundary conditions. The cavity expansion theory, founded on Solid Mechanics principles, provides the sound theoretical basis to derive the pressuremeter analytical equations. The loading and unloading pressuremeter curves can, there, be simulated using analytical equations. Solutions for the drained and undrained problems were developed. The undrained problem was solved using small and large strain analyses, while the drained problem was solved using just the small strain analysis. The solutions were based on the hyperbolic stress-strain relationship with no soil volumetric change for undrained tests and linear volumetric change relationship for drained tests. Based on these solutions, interpretation methodologies for drained and for undrained tests were presented. For both types of tests, the early portion of the pressuremeter loading curve is assumed not to represent the undisturbed soil response. Just the last points of the loading curve are used for soil parameter interpretation purposes. The unloading pressuremeter curve plays a major role in the methodology to interpret undrained tests. On the other hand, due to the soil arching and the free port water flow phenomena, the unloading portion of the pressuremeter drained test may not be used to derive the drained soil strength. For this reason, the proposed methodologies for interpreting drained SBPT's do not take into account the unloading data. All derived equations are presented and the curve fitting technique is performed using a commercially available microcomputer software. This allows any geotechnical company to use the proposed methods. Simplicity, accuracy, and reliability have been essential features of the proposed methodologies pursued since the conception of this whole work.