Abstract: This paper presents a case history of soil improvement with Cement-Fly ash-Gravel (CFG) columns project that resolving the typical characteristics of soft soil of low bearing capacity, high compressibility and poor mechanical properties. A two-dimensional plane strain finite element model using ABAQUS software with contact element between column and soil was established to evaluate the bearing capacity and settlement of the composite ground under the loading. The design parameters, column length, column diameter and spacing, were numerically investigated and optimized. The results indicated that the composite ground improved by CFG columns met the design requirement and the numerical simulated results can be used as the design guide lines for the actual project. The total settlement reduction and increasing the bearing capacity could be achieved by increasing the column length and column diameter and reducing the column spacings. However, a minimum number of columns should be maintained.

Key words: soft soils, CFG columns, post-construction settlement, foundation bearing capacity, design optimization