Effect of Overlap Distance and Chord Angle on Performance of Overlapping Soil-Cement Columns

The stress distribution in deep mixing improved columns is affected by cement content and in-situ soil properties of the surrounding soil. Group of cement improved soil column can be overlapped to form a shear wall which can support side slopes of embankments to enhance stability of the supported structure. The overlap distance of these columns is one factor that influences the efficacy of the columns and their overall effect on performance of the supported structure. This paper presents a numerical investigation on the effect of overlap distance and chord angle of overlap on the performance of soil-cement columns. The analysis of results show that the total stress on the columns decreases initially from 89.9kPa to 83.1kPa at 0 and 0.16m overlap distance due to development of discontinuities and stress concentration at corners of overlapping columns. The total stress on the column also increases between 0.16 and 0.32m overlaps corresponding to e/d ratio of 0.2 to 0.4m. This implies that values between 0.2-0.4 can be adopted for ratio of overlap distance and column diameter in design of overlapping column.