Abstract: In this paper, the penetration and expansion phases of the Flat Dilatometer Test (DMT) in sands is numerically simulated by using the discrete element method. Sandy soils with zero water content were simulated with randomly generated circular particles with grain sizes within a predefined range. The stress and strain processes of the DMT penetrating from the top to the bottom of the model were determined and plotted. The lateral stress and soil density effect on the soil stress and strain were studied respectively. The results show that: 1) the penetration and expansion process of DMT change the natural stress state and the local deformation of the soil, further affecting the mechanical behavior of the soil; 2) the penetration of DMT and the expansion of membrane will affect the vertical stress and strain of the soil, but the expansion of membrane mainly affects the horizontal stress of soil; 3) During the penetration phase of DMT, the stress change of dense soil is more obvious, while the deformation of loose soil is larger; 4) Higher lateral stress can reduce stress interference and produce slight deformation.

Key words: flat dilatometer testing, penetration and expansion, discrete element analysis, parametric study