Soluble filament 3D printing: a game-changer for experimental studies on piping stability

Internal erosion is a common incident associated with nearly half of all dam dysfunctions and failures. This phenomenon occurs when soil particles are washed out of the soil mass by seepage by way of a preferential pathway. When the seepage is strong enough, the flow can wash out coarse particles and form an elongated void referred to as a ‘pipe’. Although many analytical assessment methods have been proposed, laboratory testing using representative soil samples remains the most reliable approach. Experimental studies on the stability of piping and erosion rate commonly use pre-formed or pre-drilled straight holes, which do not adequately represent realistic piping scenarios. This paper presents a novel, validated approach using three-dimensional (3D) printing soluble filament to form pipes within reconstituted soil specimens. 3D printing technology helps to form the pipe at any size and shape, while the soluble filament dissolves in water without inducing significant mechanical disturbance to the surrounding soil. Transparent hydrogels were used to observe the dissolution process of 3D-printed pipe walls, and the approach was further verified using cohesive soils. Test results confirmed that the formation of pipes using 3D soluble filament has negligible impacts on soil pipe stability.