Development of a Laboratory Scale Pressuremeter for use in Loose Sands

Event Summary

Characterizing the shearing behaviour of loose sands is challenging due to the large shear strains required to fully mobilize their response. Conventional pressuremeters typically reach maximum cavity strains of only 10-15%. Since shear strain decays exponentially with distance from the probe wall, this strain range is often too small to capture the full behaviour of loose sands, and larger cavity expansions are needed. To address this, research was conducted that aimed to develop a laboratory-scale pressuremeter capable of achieving at least 20% cavity strain.

A laboratory-scale pressuremeter developed by the University of Western Australia (UWA) in 2013 used compressed air and strain-gauge-equipped feeler arms to measure radial deformation. Building on this design, two additional probes were evaluated: a mechanically identical University of Saskatchewan (USask) built clone of the UWA probe, and a new probe incorporating two orthogonal linear variable differential transformers (LVDTs) to directly measure radial expansion over a larger strain range. Testing was conducted in kaolinite and a uniform fine sand, supported by conventional laboratory characterization to establish baseline strength and stiffness parameters.

Preliminary results demonstrate that the LVDT-based design effectively captures expansion and produces high-quality pressure-expansion curves, though maximum strains reach only 12-13% and contraction was difficult to measure. This research evaluates the performance of the UWA/USask design, outlines the development of the new LVDT-based pressuremeter, and presents proof-of-concept testing for both laboratory scale pressuremeter designs.