Development and operation of an automatic air pluviation system for physical modelling applications

This paper presents an air pluviation system, developed to facilitate 1-g physical model tests in granular soils. The deposition process is fully automated and requires minimal input from the operator, thereby significantly reducing the time required to deposit large volume of granular material, improving the uniformity of the prepared specimens, and the reliability of test results. The components comprising the pluviation system have been calibrated to produce loose-to-very dense sand beds, of relative density that ranges between Dr=7% and Dr>100% of the maximum density achieved with the procedures described in the pertinent standards. The testing chamber where sand is deposited is instrumented with an array of pressure sensors, and the rig is equipped with a miniature Cone Penetration Testing (mini-CPT) device. Measurements from the earth pressure sensors and cone tip resistance profiles are used to evaluate how friction at the sand-chamber interfaces affects the distribution of geostatic stresses inside the chamber, the uniformity of sand beds, and boundary effects during deposition and during mini-CPT testing. The air pluviation system allows preparing layered sand profiles by adjusting the deposition parameters on the fly, and this feature is demonstrated via the analysis of mini-CPT tests performed in layered sand beds.