Reinforcing soft soils with artificially cemented compacted-sand columns

Compacted-stone or -sand columns have been used increasingly during the past two decades as a technique to reinforce soft cohesive soils and increase bearing capacity, accelerate consolidation, and improve the settlement response of the foundation soil. The bearing capacity of the granular column is governed mainly by the lateral confining pressure mobilized in the native soft soil to restrain bulging collapse of the granular column. Therefore, the technique becomes unfeasible in soft, compressible clayey soils (i.e., undrained shear strength less than 15 kPa) that do not provide sufficient lateral confinement. This paper presents the main results of an experimental study of the feasibility of using artificially cemented, compacted-sand columns in the reinforcement of soft cohesive soils. Triaxial compression tests are conducted on composite-reinforced soil samples made of annular, normally consolidated, kaolinite, reinforced by both cemented and untreated columns of river sand. The test results provide a preliminary data base for a fundamental understanding of the cementation effect on the performance of the granular column, and for a quantitative evaluation of the group effect on the settlement response of the reinforced soil.