The use of tactile pressure sensors for horizontal stress measurements on a large flexible Calibration Chamber

Large flexible calibration chambers (CC) to evaluate and develop interpretation methods for cone penetration tests (CPT) in cohesionless soils have been used since the late 1960s. Nevertheless, only average boundary stress values are known in almost all tests already performed. Tactile Pressure Sensors represent a useful tool to assess the stress distribution in an area under loading and have been applied in some geotechnical studies. The present study presents the results of CPTs carried out on a large flexible CC in a very loose and a medium dense fine quartz sand. Tactile pressure sensors were placed on the walls of the CC, allowing the measurement of horizontal stresses and their spatial distribution in all test phases: sample formation, lateral and cavity cell filling, piston filling, sample stressing, and CPT. In particular, the Tactile Pressure Sensors were able to measure the horizontal stresses before the cavity and lateral cell filling, i.e. when no information is available about the horizontal stresses in regular tests. The measurements contribute to the discussion on the influence of the CC boundaries on the test results. The results encourage the use of tactile pressure sensors in a more routinely base in large flexible CC testing.