Water retention behaviour of 3D-printed double-structured soil

Abstract

3D printing of soils is an emerging additive manufacturing technique that is gaining significant attention across various fields, due to its high level of automation and low environmental impact. Interestingly, also geotechnical engineering applications can benefit from this technique in the future, exploiting the fact that 3D-printed soils can exhibit a peculiar fabric with a distinct bi-modal pore network. These double-structural levels can be adjusted within certain limits due to the design flexibility offered by 3D printing. Current applications of 3D-printed soils rely primarily on empirical criteria, and the existing literature remains in its early stages, particularly lacking a geomechanical perspective. Advancing the understanding of the hydro-mechanical behaviour of these materials is essential-not only to predict their performance in future applications but also to refine the early-stage printing processes currently in use. To address this, the present work focuses on investigating the complete hydro-mechanical behaviour of 3D-printed soil with the special attention to its water retention behaviour. Several 3D-printed samples with a clear double-structure fabric were printed and subjected to drying and wetting paths from the as-printed state, to reconstruct the water retention curves. A novel method was employed to monitor volumetric changes in the samples, using a 3D laser scanner to capture volumetric variations at two microstructural scales. Moreover, fabric analyses through different stages of drying/wetting paths were performed using Mercury Intrusion Porosimetry and Scanning Electron Microscopy. Finally, the water retention behaviour of 3D-printed soil samples was modelled, considering their double-structure nature, and key characteristics of this behaviour are discussed in detail.