Ground Improvement for Transportation Infrastructure: Experimental Investigations on Cyclic Behavior of a Group of Granular Columns

Abstract

This paper presents the results of experimental and numerical investigations conducted on groups of granular columns under loading conditions similar to transportation routes. Cyclic and monotonic tests were conducted on reduced-scale groups of floating and end-bearing granular columns of 30 mm diameter installed in very soft clay beds of two different undrained shear strengths of 6 and 10 kPa and arranged in plane-strain state to simulate the loading conditions present in transportation routes such as highways and railways. The measured results for floating and end-bearing groups of stone columns under monotonic loading are then validated numerically using three-dimensional finite-element analyses. The experimental results show that the settlements induced by cyclic loading are nearly 4–11 times greater than the settlements induced by monotonic loading of the same magnitude of maximum vertical stress. The end-bearing granular columns are observed to be more effective than floating granular columns in improving the bearing capacity of the soft ground and reducing the induced settlements under both cyclic loading and monotonic loading. The results of three-dimensional finite-element analysis show that the major deformation for peripheral columns in both floating and end-bearing stone column groups is lateral, whereas the central columns either undergo shortening and punching in the case of floating stone columns or bulging in the case of end-bearing stone columns.