Development of a calibration chamber for a novel in situ testing device

The paper presents the design of a calibration chamber, developed for the testing of a novel self-burrowing probe for in situ soil investigation. The self-burrowing probe is currently under development at ETH Zurich, and its key components will be proof-tested in the controlled environment of the developed chamber. The design of the latter incorporates specific solutions for the testing of the probe: the chamber is equipped with a central opening at the top and base plates, enabling the probe to vertically protrude from the chamber. This aspect is useful for eliminating the tip resistance of the probe and isolating its response, which is relevant when assessing the resistance of the probe’s anchoring system or, in general, for the evaluation of interface properties. The chamber allows for testing under two boundary conditions: (i) zero lateral strain or (ii) constant lateral stress. In the latter case, the radial stress is applied by water pressure inside a membrane, while a pneumatic, doughnut-shaped cushion at the base is used to impose the vertical stress. The paper outlines the key components of the chamber, the sample preparation, and the testing procedures, along with the results of the proof tests conducted in dry Perth sand.