Experimental investigation of colloidal silica gel stabilized sand behaviour
The research program aims to develop a formalized method of predicting the behaviour of stabilized sands and to verify the robustness of the notion of their enhanced resistance to shearing through an extensive experimental investigation. The cementing agent is a dilute solution in water of colloidal-silica (CS) particles, with an average diameter of 7 nm. The solution is pH-responsive and turns into a gel in a controllable manner. The gel fills the pore space, retains the pore water and supports the grain structure. A granular and a rounded sand will be tested to assess grain interaction with the gel.
The literature suggests that sand stabilized with silica gel shows enhanced dilatancy and liquefaction resistance compared to untreated sand. However, a paradox exists at the heart of treated sand behaviour; as it is softer compared to the untreated parent sand in resonant column tests, exhibits higher rates of strain and excess pore water pressure accumulation under cyclic loading and shows higher compressibility under normal compression Georgiannou et al. (2017).
Given that upon shear loading a transition of the gel itself to a viscoelastic liquid is reported in the literature, cyclic loading may indicate this effect in the macroscopic response of the treated sand. The contradictory behaviour mentioned above will be investigated on the basis of an extended database of static and cyclic/dynamic tests.
The testing program will concentrate on cyclic and dynamic loading following the same stringent experimental procedures employed in past monotonic loading tests 
so that a unified framework of stabilized sands’ behaviour under static and dynamic loading will be proposed using as a reference the untreated sands’ behaviour. This comparison will demystify the role of the gel and will lead to the development of formalized constitutive relationships.
Funding: (NTUA’s Basic Research Framework Program, PEVE). 2021-2023