Analysis of soil‐structural interface behavior using three‐dimensional DEM simulations

Abstract

The shear behavior at the interface between the soil and a structure is investigated at the macroscale and particle-scale levels using a 3-dimensional discrete element method (DEM). The macroscopic mechanical properties and microscopic quantities affected by the normalized interface roughness and the loading parameters are analyzed. The macro-response shows that the shear strength of the interface increases as the normalized roughness of the interface increases, and stress softening and dilatancy of the soil material are observed in the tests that feature rough interfaces. The particle-scale analysis illustrates that a localized band characterized by intense shear deformation emerges from the contact plane and gradually expands as shearing progresses before stabilizing at the residual stress state. The thickness of the localized band is affected by the normalized roughness of the interface and the normal stress, which ranges between 4 and 5 times that of the median grain diameter. A thicker localized band is formed when the soil has a rough shearing interface. After the localized band appears, the granular material structuralizes into 2 regions: the interface zone and the upper zone. The mechanical behavior in the interface zone is representative of the interface according to the local average stress analysis. Certain microscopic quantities in the interface zone are analyzed, including the coordination number and the material fabric. Shear at the interface creates an anisotropic material fabric and leads to the rotation of the major principal stress.KEYWORDS discrete element method, fabric anisotropy, localized band, soil-structural interface | INTRODUCTIONIn geotechnical engineering, the soil-structural interface is involved in many roles, including roles in deep foundations and geogrid reinforcement engineering and the role of serving as the anchor for retaining walls. The diverse mechanical properties of the soil that interacts with the interface have attracted growing attention from the research community 1-3 . The shear behavior of the soil-structural interface is one of the most significant properties in engineering design and in numerical modeling of geotechnical engineering problems. 4-6 Previous investigations have primarily relied on experimental approaches, namely examining macroscopic observed phenomena, to characterize the mechanical behavior of the interface. 7-13 However, these investigations failed to properly explain the micro-

3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness

“…In [55], the boundary conditions along the horizontal rigid wall suggested inclusion of two ratios connected to the normalized wall roughness (a ratio of the micro-polar rotation multiplied by the mean grain diameter and the horizontal displacement and a ratio of the horizontal shear stress multiplied by the mean grain diameter and the horizontal couple stress). To better understand microscopic phenomena during wall friction, DEM calculations were also carried out [4,5,12,14,15,22,24,25,62,63,70,77,78]. There exist many numerical studies of wall friction using DEM under 2D conditions (e.g.…”

“…There exist many numerical studies of wall friction using DEM under 2D conditions (e.g. [14,15,22,62,63,77,78]) and only a few under 3D conditions [4,5,12,24,25,70]. To facilitate the interpretation of macroscale responses, microscale metrics such as contact normal force distribution, contact networks, mobilization of friction, and particle rotation were calculated to elucidate the wall friction mechanism.…”

A closed-form solution for column-supported embankments with geosynthetic reinforcement

“…Note that negative skin friction develops at the column shaft, increasing the stress and compression on the column and reducing the stress and compression in the surrounding soil. The deformation shape of the latter is hard to determine and is influenced by certain factors, such as soil structure interactions (Zhou and Yin, 2008;Yin and Zhou, 2009;Su et al, 2010;Zhou et al, 2011;Hokmabadi et al, 2014;Suleiman et al, 2016;Meguid et al, 2017;Yu and Bathurst, 2017;Zhu et al, 2017;Jing et al, 2018;Wang et al, 2018b) and constitutive models adopted for subsoil (Yin et al, , 2010a(Yin et al, , 2010b(Yin et al, , 2011a(Yin et al, , 2011bSexton et al, 2016;Yin et al, 2017). Alamgir et al (1996) innovatively proposed a deformed shape function to investigate the performance of a column-reinforced foundation, which is applied here for this purpose.…”

Observations on fabric evolution to a common micromechanical state at the soil‐structure interface

“…Wang and Jiang, via a comparison between interface and direct shear test methods, showed that the SSI's shear strength is essentially the mobilized soil strength of the rough surface. In a later paper, Jing et al reported that for an SSI rougher than a certain value, the shear strength can be approximate to the strength of the soil itself. In fact, a soil phase with a highly nonlinear constitutive behavior gives rise to a complex mechanical response of SSI to the shear load.…”