The installation of soil-cement columns causes excess pore-water pressures and movements of surrounding ground, which affect adjacent underground structures. In Shanghai, a triple-shaft deep soil mixing (DSM) method has been proposed and is widely used to minimize the installation effects. However, when this DSM method was used to install soil-cement columns close to a Metro tunnel, unacceptable soil displacement was caused, even at the very beginning. Therefore, it was decided to conduct field tests to investigate the effect of major factors affecting DSM installations and then modify the construction parameters so that the soil displacement caused by DSM construction would not exceed the allowable limit. The field tests consisted of two phases: Phase I tests of single DSM column installations close to the Metro tunnel to modify the construction parameters, and Phase II tests of continuous multiple DSM column installations far from the Metro tunnel to validate the modified construction parameters...

This study proposes a practical method for determining active earth pressure of confined cohesionless soil. A trapezoidal thrust wedge model confined by two vertical rigid retaining walls is developed to derive the governing equations of earth pressure distribution and the resultant force. The resultant force depends on the unknown incline angle of the sliding plane and must be maximized with respect to the angle. The active earth pressure can be determined once the incline angle is obtained by solving the governing equations with the finite-difference method. Based on these equations, parametric studies are conducted to investigate the effects of the confined width on the active earth pressure and the inclination of the sliding plane. As expected, the active earth pressure decreases with the confined width due to the arching effect. In contrast, the incline angle of the slip plane in the confined cohesionless soil is in close proximity to that of Coulomb’s solution. Moreover, the incline angle of...