Effect of Column Elasticity Modulus on Composite Foundation Failure of Deep Mixed Columns

Currently, studies on the overall stability of deep mixed columns are mainly based on the assumption that the columns are subjected to shear or bending failure. In this study, a finite difference method was used to determine the stress characteristics of columns in different positions. The failure mode and development direction of the failure process of composite foundations were investigated. Next, the effects of elastic modulus on the stress, failure mode, and failure sequence of the columns were analyzed. The results show that under the action of embankment loads, the composite foundation of deep mixed columns exhibits two failure modes: bending and shearing. The stress of deep mixed columns significantly varies with spatial distribution. Under the action of embankment loads, the column failure is progressive, and the columns beyond the slope shoulder are more prone to bending failure. The failure first occurs at the slope foot and gradually extends to the center of the embankment. However, the columns inside the embankment is more prone to shear failure, and the failure direction extends from the embankment center to the slope foot. As the elastic modulus of the columns increases, the column failure mode changes from shear failure to bending failure. The composite foundation of low-modulus deep mixed columns initially experiences internal shear failure and then, bending failure, at the slope foot. Conversely, the high-modulus deep mixed columns tend to crack before bending at the foot of the slope, and subsequently, shear failure occurs. The increase in the elastic modulus increases the bending rigidity of the columns, causing them to resist more bending moments and become more prone to bending failure. © 2020, Editorial Department of China Journal of Highway and Transport. All right reserved.