Chamber studies of the effects of pressuremeter geometry on test results in sand

The pressuremeter test has proved to be a useful tool for geotechnical engineers to determine the in situ properties of soils. However, results indicate that the strength values derived from pressuremeter tests are often quite different from those obtained from good laboratory tests and other in situ tests. It is believed that a major part of this disagreement may be due to the influence of pressuremeter geometry. This is because, in most analyses, the pressuremeter is assumed to be infinitely long, although commercial pressuremeters are of finite length. Therefore, it is necessary to investigate the possible effect of the finite pressuremeter length on soil parameters derived from the tests. A two-dimensional axisymmetric finite-element analysis was used to simulate pressuremeter tests. It was found that the finite pressuremeter length has a significant effect on derived soil properties. Experimental studies on the effect of a finite pressuremeter length reported in the literature are not sufficiently comprehensive to reach a definite conclusion about the effect of pressuremeter geometry on derived soil properties. In the present study, therefore, a large number of pressuremeter tests with four different length/diameter ratios (L/D = 5, 10, 15, 20) were conducted in a 1 m x 1 m calibration chamber located at the University of Newcastle, Australia. Based on the results of those laboratory pressuremeter tests, experimental correlations are presented which can be readily used in practice to account for the effect of pressuremeter geometry on the derived soil properties.