Evaluation of self-penetration potential of a bio-inspired site characterization probe by cavity expansion analysis

Abstract

Site investigations at limited-access project sites often require mobilization of smaller rigs that may not have the reaction mass required to perform soundings to the desired depth. This study explores the feasibility of a new conceptual bio-inspired solution by adapting functional principles from organisms whose primary mode of locomotion is soil burrowing, including razor clams, caecilians, and earthworms. These organisms radially expand a segment of their body to increase the normal radial pressure acting on it to temporarily form an anchor. This study evaluates the dimensions required for self-penetration of an idealized bio-inspired probe consisting of a radially expanding shaft and a penetrating tip. Cavity expansion analyses, field test data, and theoretical relationships from the literature are used to evaluate the self-penetration potential in different soil types. The results indicate that the resistance to self-penetration is higher in dense sands than in silts and clays. In sands, the resistance to self-penetration is greater for sands that exhibit a more dilative behavior at a given overburden pressure. On the contrary, the resistance to self-penetration in clays decreases slightly as the overconsolidation ratio is increased. The relative dimensions required to initiate self-penetration predicted by cavity expansion analysis are compared with the dimensions of various burrowing organisms.