Experimental study on self-burrowing dual anchor soft probe

Abstract

This study focuses on the development and testing of a bio-inspired self-burrowing dual anchor soft probe for potential geotechnical applications. Dual anchor refers to the form of movement in soils in which some bivalve molluscs adopted by alternately generating anchoring effects in the soil through shell expansion and fluid-filled feet. By mimicking this mechanism, this study used pneumatic artificial muscles as soft actuators and developed an autonomous burrowing probe. The structure and the performance of the actuators and the probe were investigated and optimized. The burrowing-out process of the dual anchor probe was not a simple upward movement. Instead, it rose in the inflation phase and slipped downward in the deflation phase. The difference between the two was a stride in one single step. In the sands with relative densities of 30%, 50%, and 80%, the total slips accounted for 18.8%, 19.6%, and 26.9% of the total upward movements, respectively. Thus, the entire movement process showed a reciprocating upward trend. The burrowing process could be divided into a restricted stage and a free stage according to whether shear failure occurs in the overlying soil layer. When the soil density was high, the initial stage of burrowing was in a restricted stage. The amount of rise and slip were at a low level and increased slowly as the number of cycles increased. When the burrowing process was in the free stage, the increase was basically stable at a high value and accompanied by small slips.