Drawings of a new experimental device for the visualisation of fluid-driven cracks in clays. In the proposed experimental device, a thin layer (~1mm) of clay paste is compressed between two transparent discs of 110 mm diameter and 50 mm height. The bottom disc has a central hole through which a steel pipe is inserted to inject the fluid at the centre of the clay sample through a tip filter. A perimeter filter contains the sample laterally while allows to control the back-pressure during the fluid injection. The transparent discs and the perimeter filter are positioned by means of three steel rings, which are guided by four precision shafts. The compression of the clay sample is achieved by tightening nuts at the threaded ends of the shafts.
The device is instrumented with four donut load cells (one per shaft) placed in between the tightening nuts and the top ring to measure the compression forces, two displacement traducers (LVDT) to measure the relative displacement of the transparent discs, and fluid pressure transducers connected to the injection pipe and to the perimeter filter. The experimental setup is completed with two high-precision high-pressure pressure-volume controllers, that permit to control fluid injection rate and the back-pressure. In addition, pictures are taken with a high-resolution camera at a regular rate during the fluid injection, through the top transparent disc. To enable the detection of thin cracks, the device and the camera are placed in a dark box, with a collimated backlight panel placed under the bottom transparent disc.
This device has been developed as part of the GASCLAY project funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101028292.