Lab Model Test of Laterally Restrained Sand Pile

Lab model test has been one of the most important methods to study the reinforcement mechanism of composite foundation and the effect of reinforcement to foundations of this type. In light of the interaction mechanism, the author creates several model sand piles by making closed cylinder molds with 70g standard A4 paper (or newspaper) as the packing material, and then fill in the inside of the cylinder molds with separate layers of sand. Similar to the way inter-pile soil laterally restrains sand pile in a composite foundation, the cylinder molds apply lateral restraining force on the sand inside. For the purpose of verifying the reasonability of the model pile and exploring how the strength of the packing material, the compacted density of the filler, and the sectional area of the confinement impact the vertical bearing capacity of the model piles, the author conducts loading tests on the model piles with a self-designed lab loading device and compares the results with those generated from similar tests performed with a loading press. The results show that the vertical bearing capacity of sand piles could be significantly improved by applying lateral restraining force within a certain range on the top of the pile; the strength of packing material determines whether the model sand piles would end up in buckling or bulging failure, the vertical bearing capacity of the model piles increase with the mean compacted density of the packing material, and the sectional area of the confinement indicates the magnitude of the restraining force exerted from the packing material upon the filler inside, which not only affects the bearing capacity but also the failure location of sand piles.