Visualization technique in a laboratory experiment for the deformation distributions of subsidence of aquitard over aquifer due to excess pumping

Visualization methods using transparent synthetic soils (TSS) have been developed as a physical model of macroscopic soil behavior from a geotechnical engineering perspective. Transparent surrogates containing transparent porous media and pore fluids have been used to simulate the geotechnical properties of natural soils. Studies to experimentally verify local deformation in subsidence phenomena require the use of inexpensive laboratory industrial materials to understand the macroscopic scale of larger test models. TSS made of polymeric polymers used in this experiment are one of those employed to accomplish this need and are easy to handle. In the present study, a larger-scale pumping test than previously reported was conducted using a 300 mm wide x 250 mm long x 249 mm high acrylic tank filled with transparent hydrated polymer to represent an aquitard (clay layer) over an aquifer (saturated silica sand). Settlement within the synthetic clay layer due to pumping of pore water from the silica sand was constantly monitored by the target racking method using 100 particles of 3 mm diameter immersed in the synthetic clay layer. This experiment successfully visualized the deformation inside TSS due to vertical propagation of pore water pressure in the TSS during pumping and after pumping, in more detail than in the previous experiment. The experimental results showed good agreement with the numerical results of the three-dimensional pore-plastic deformation theory.