Reliability-based design of stone columns for ground improvement considering two settlement failure modes. The necessity of preloading

摘要

This paper studies stone column under uncertainty, analyzing two settlement failure modes: ⅰ) "remaining" settlements, or settlements occurring after some waiting period; and ⅱ) "total" settlements, or settlements occurring since application of the load acting on the improved ground. An improved theoretical solution that considers the influence of the radial deformation and yielding of the column on the (radial only) consolidation analysis is employed. Reliability methods are used to consider the effects of uncertainties on the probability of failure under both failure modes. To work with realistic values of geotechnical parameters, data are taken from a real soil improved with stone columns. The main conclusion of is the necessity of pre-loading the ground improved with stone columns so that settlements occur before application of the load associated to the permanent structure. Otherwise the probability of failure can be very high, even in cases in which the deterministic margin of safety may be sufficient.