Utilisation of extrusion method in geotechnical tests: conception and theoretical analysis

Abstract

Extrusion method has been utilised in a variety of product-processing units such as metal casting and food processing. The process of extruding is relatively fast and reproducible, and more importantly, can benchmark shear resistance of extruded materials. These advantages have propelled researchers to practice the extrusion method to determine soil properties, e.g. Atterberg limits and shear strength. Although the mechanics behind the extrusion process remains less understood, studies have verified the feasibility of the benchmarking. This study presents the theoretical basis underpinning the extruding process by extending the conventional slab analysis method to model the entire process of extruding. The developed analytical method is original in assessing the extrusion of the dead material zone and considering the dynamic move of extruded materials. The novel theoretical analysis enhances a more accurate estimation of extruding pressure and builds a solid foundation for developing extrusion tests in geotechnical engineering. In addition, the described extrusion mechanics explains reasons for observing some discrepant correlations to other geotechnical parameters due to the different soil deformation mechanisms among the test methods.