عنوان مقاله [English]
In-situ tests are reliable for determination of soil properties since larger amount of soil is tested in real stress levels. Pressuremeter is one of the most important in-situ tests in geotechnical engineering. The main advantage of this instrument is the continuous measurement of soil stress-strain curve which is applicable to determination of soil parameters using cavity expansion theories. In this study, self-boring pressuremeter test has been modelled using the commercial FLAC software. The soil is assumed to behave elastic-perfectly plastic, and the Mohr-Coulomb constitutive model is chosen. The results of the numerical analyses are validated by the measurements of in-situ pressuremeter test results which can be found in the literature. Effect of cavity diameter on the cavity expansion curve is observed because pressuremeters have various diameters. It can be concluded that cavity diameter has no effect on cavity stress-strain curve obtained from numerical analysis. Also, the difference between small deformation and large deformation analysis of cavity expansion curve has been assessed. Results show that in the strains smaller than 10 percent, the difference is marginal. Since cavity is generally expanded up to 10 percent strain in the pressuremeter test, small deformation analysis can be applied to the interpretation of this instrument. After that, different theoretical methods of cavity expansion have been compared to the results of numerical analysis. Theoretical methods are based on assumptions which are not appropriate for all conditions and consideration of all aspects of soil behavior is not feasible due to complexity. Also, theoretical and empirical
methods of interpretation of pressuremeter test for estimation of internal friction angle are evaluated. Some theoretical methods are based on unloading portion of pressuremeter stress-strain curve due to fewer disturbances. It is realized that empirical methods have greater errors in prediction of friction angle in comparison to theoretical approaches. An optimized method is proposed for estimation of friction angle.