Push-up Load Tests Using Uncrushable Particles and Its DEM Analyses

Abstract

In this study, push-up load tests of soil plugs having various aspect ratios in a steel pipe pile and its DEM analyses were carried out. Uncrushable uniform spherical particles (alumina balls) were used to model soil plugs. In order to obtain physical properties of the alumina ball, element tests of alumina balls, including one-dimensional compression tests and direct shear tests, shear tests between the model soil and the model pile and so on, were carried out. Then, DEM analyses of the one-dimensional compression tests and direct shear tests were carried out by matching the DEM results with the results of the element tests to obtain the analysis parameters to be used in DEM simulations of the push-up load tests. Thereafter, the push-up load tests and its DEM simulations were carried out. The results showed that the maximum push-up force increases with increase in aspect ratio and that hardening and softening behaviour of the push-up force occurs. These behaviours were totally in accordance with the experimental results. Finally, the experimental results in this paper are compared with the push-up load tests of the crushable sand plugs obtained in previous study, in which the push-up force increased monotonically with increasing push-up displacement. Possible influence of crushability of particles on the plugging behaviour during push-up loading is discussed, based on the comparison.