Analysis of self-boring pressuremeter (SBPM) and Marchetti dilatometer (DMT) tests in granite saprolites

Abstract

This paper presents the analyses of the results of the site investigation programme carried out at the Kowloon Bay site in Hong Kong. The tests consisted of self-boring pressuremeter (SBPM), Marchetti dilatometer (DMT), and laboratory tests carried out in a granite saprolite, which can be described as a lightly cemented sand. The purpose of this research project is to stimulate the development of methods to interpret data obtained from tests in residual soils. In particular, the work aims to evaluate the analyses of the SBPM data through a curve-fitting technique. Both the loading and unloading portions of the SBPM curve were analysed and the results compared with those from other tests. The advantage of this analysis technique is the possibility of constructing a theoretical curve that reproduces a pressuremeter test from which a set of fundamental parameters can be derived, namely the friction angle, cohesion intercept, lateral stress, and shear modulus. The DMT proved to be a reliable tool that yielded good soil parameters at a small fraction of the cost of the other in situ tests.Key words: residual soil, in situ tests, pressuremeter, Marchetti dilatometer.

Site Investigations of the Lacustrine Clay in Taihu Lake, China, Using Self-Boring Pressuremeter Test

“…By assuming the soil is perfectly elastic during the unloading process, the gradient of the unloading–reloading cycle is thereby twice the linear shear modulus (i.e., 2 G ur ), where G ur is also referred to as the unloading–reloading shear modulus [ 7 , 16 ]. Bolton and Whittle [ 26 ] showed that the power–law function can well describe the variation of the shear stress with strain, i.e., where and are the stiffness constant and elastic exponent, respectively, which can be derived from the reloading data of the unloading–reloading cycles.…”

“…Ferreira and Robertson [ 14 , 15 ] developed a method that incorporated nonlinear soil behavior, with both loading and unloading portions of the test to interpret SBPM results. Schnaid et al [ 16 ] proposed a curve-fitting technique to interpret the granite saprolite parameters derived from the SBPM test, and the results were compared with other tests, including dilatometer and laboratory triaxial tests. By analyzing the test results obtained from SBPM in a sensitive Champlain clay of Quebec, Silvestri [ 17 ] concluded that the SBPM test did not overestimate the undrained shear strength, as opposed to the vane shear test results.…”