Bearing capacity of composite foundation of soil-cement deep mixing columns with different cross-section parts

The soil-cement deep mixing column with different cross-section parts is a new kind of soft soil foundation treatment methods. Since special modifications have been made against those drawbacks which exist in traditional deep mixing columns, the soil-cement deep mixing column with different cross-section parts exhibits good foundation treatment effect and thus has been gradually popularized in China recently. Based on in situ static load tests in subsoil of Huzhou in Zhejiang province, the bearing capacity and load transfer mechanism of single column composite foundation of soil-cement deep mixing columns with different cross-sections are studied. The result shows that load transfer is limited to a certain range due to soil-cement strength of column body. Stress concentration appears at the position of cross-section variation. Axial force decreases with depth. The maximum lateral friction resistance occurs at the depth of 4D-6D below the loading plate (D is diameter of upper column). The lateral friction resistance below varied cross-section decreases sharply due to the end resistance effect of the varied cross-section. The end resistance under varied cross-section increases with the total load in the beginning, then it tends to be stabilized. As the length of upper column part increases under the same condition, the end resistance under varied cross-section decreases, but the column-soil stress ratio increases.