Numerical Simulation of the Effect of Void Direction and Volume on the Strength of Cemented Soil

A void can be formed or expanded in a weakly cemented in situ soil because of multiple reasons such as abandoned old pipes and eroding of fine particles caused by pipe leakage. Such void formation can develop into various directions and amounts of volumes, which can influence the engineering behavior of in situ soils. In this study, a distinct element method was employed to quantitatively investigate the effect of such void formation on the strength of cemented soil. An empty capsule was vertically or horizontally embedded in cemented sand for void simulation, which was tested for its unconfined compressive strength (UCS). The experiment result was used to calibrate the built-in bonded particle model in PFC2D computer code. The effect of void formation direction and volume on the strength of cemented soils was numerically investigated in terms of UCS. Consequently, the UCS of cemented sand significantly decreased up to 64% as embedded capsules changed from the vertical to the horizontal direction. The UCS of cemented sand linearly decreased down to 63.2% as the number of capsules increased from 1 to 4. The decrease in strength was because the void area disconnected the shear bands - explicitly represented as broken bonds - and trapped the distributed stress inside the layers between capsules, resulting in a lower strength of the specimens.