Particulate-Sensor Interaction and Its Influence on Stress Measurements in Granular Media

Accurate pressure measurements in soils and other particulate media are essential for the development and validation of engineering models. Pressure transducers based on deflecting membranes remain widely used despite longstanding recognition that sensor deformation may influence the measured response. This study investigates the extent to which hysteresis observed during load–unload cycles originates from sensor–material interaction rather than intrinsic material behavior. Controlled experiments were conducted on dune sand and uniform glass beads using sensors operating in membrane-deflection mode and Null mode, together with direct measurements of local material deformation. The results show that even small membrane deflections generate pronounced apparent hysteresis and that conventional calibration procedures cannot reliably eliminate this effect, even when performed under matching test conditions. The resulting measurement errors become particularly significant during unloading. Direct observations reveal that during loading, the surrounding soil accommodates the elastic deflection of the membrane. During unloading, however, the surrounding soil does not accommodate membrane recovery, preventing the membrane from rebounding along its elastic path. In contrast, Null-mode measurements exhibit a nearly unique response with substantially reduced hysteresis and little dependence on sensor stiffness. The findings indicate that a significant portion of hysteresis commonly reported in pressure measurements may reflect measurement-induced effects rather than intrinsic material behavior, highlighting the importance of accounting for sensor–material interaction when interpreting experimental data and validating engineering models.