ANALYSIS OF NON-EQUAL STRAIN AND NONLINEAR CONSOLIDATION PROPERTIES OF STONE COLUMN COMPOSITE FOUNDATION

The existing consolidation theory of stone column composite foundation is typically based on the assumption of equal strain, which differs from the actual engineering situation. Using the piecewise linear method, we establish a more applicable nonlinear consolidation model for a stone column composite foundation under complex conditions. This model considers the penetration of stone columns into the cushion or underlying stratum, correcting for the equal strain assumption. Additionally, the model accounts for the self-weight of stone columns and soil, the smear zone, well resistance effect, time-dependent loading, attenuation of additional stress of stone columns and soil along the depth direction, and any nonlinear compressibility and permeability relationships. In comparison with the project, the calculated results of the model are generally in agreement with the measured values. Combined with the analysis of numerical examples, we further investigate the influence of cushion and underlying stratum modulus, additional stress attenuation, and stress path on the consolidation properties of the stone column composite foundation. The results indicate that the penetration of stone columns into the cushion or underlying stratum reduces the pile-soil stress ratio, increases settlement, and slows down the consolidation rate of the composite foundation. Ignoring the additional stress attenuation of stone columns and soil has little effect on the consolidation rate but will overestimate the settlement of the composite foundation. Different stress paths have significant effects on the consolidation properties of the stone column composite foundation, and a simplified compressibility relationship of the soil layer will introduce large errors into the analysis results.