Model tests on geotextile-encased granular columns under 1-g and undrained conditions

This paper investigates the effects of encasement stiffness and strength on the response of individual geotextile encased granular columns embedded in soft soil through model tests. Similarity analysis was first executed to determine the suitable properties of the constituents used in the model tests to ensure that the prototype-scale and model-scale geotextile encased granular columns exhibit comparable behaviour.Experimental results show that encasement improves the bearing capability of all modelled sand columns, even when encasement rupture occurs; marked improvement is achieved for sand columns encased with geotextiles of relatively medium to high stiffness. Encasement also restrains the radial strain of the columns significantly. Predominate bulging of the encased sand column occurs in the top 2.5D depth of sand columns encased with low stiffness geotextile, however, sand columns encased with relatively high stiffness geotextile exhibit roughly uniform lateral deformation along the height of the column. The bearing stresses of the encased columns modelled in this study agree well with values predicted by an analytical solution using cavity expansion theory.