Generalized column method for calculation of settlement of T-shaped deep mixed column composite foundation under embankment load

T-shaped deep mixed column is a new type of soil-cement deep mixed column with varied cross-section areas. In this study, the T-shaped column is simplified as the conventional shaped column with varied deformation modulus with some assumptions. The settlement calculation method of T-shaped deep mixed column composite foundation called generalized column method is presented. Based on the displacement and stress continuity, the embankment, improved area and substratum are treated as a whole. The settlement calculation models for composite foundation under embankment load are developed considering the penetration of column tops, interaction between columns and surrounding soil, and penetration of column ends. A finite difference method is used to carry out the calculation. Based on the 3D numerical simulation results, a simplified method is proposed to calculate the additional stress in substratum under embankment load. The proposed methods are employed to calculate the settlement in field sites, and the results are compared with the measured data as well as the results calculated by other methods. The comparisons indicate that the settlement calculated using the composite modulus method is smaller than the observed data, while the calculated data using the modified stress method is too larger than the observed data. However, with the proposed method, the calculated data is well consistent with the measured data.