3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness
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RESEARCH PAPER
3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness A. Grabowski1 • M. Nitka1 • J. Tejchman1 Received: 20 March 2020 / Accepted: 22 September 2020 The Author(s) 2020
Abstract The paper deals with three-dimensional simulations of a monotonic quasi-static interface behaviour between cohesionless sand and a rigid wall of different roughness during wall friction tests in a parallelly guided direct shear test under constant normal stress. Numerical modelling was carried out by the discrete element method (DEM) using spheres with contact moments to approximately capture a non-uniform particle shape. The varying wall surface topography was simulated by a regular mesh of triangular grooves (asperities) along the wall with a different height, distance and inclination. The calculations were carried out with different initial void ratios of sand and vertical normal stress. The focus was to quantify the effect of wall roughness on the evolution of mobilized wall friction and shear localization, also to specify the ratios between slip and rotation and between shear stress/force and couple stress/moment in the sand at the wall. DEM simulations were generally in good agreement with reported experimental results for similar interface roughness. The findings presented in this paper offer a new perspective on the understanding of the wall friction phenomenon in granular bodies. Keywords DEM Interface Sand Wall friction angle Wall roughness Wall shear zone
1 Introduction Soil–structure interfaces are frequently encountered in geotechnical engineering, e.g. foundations, tunnels, retaining walls, anchors, silos, piles and geotextiles. They play a major role in the interaction between soils and structures with respect to a static, dynamic and fatigue mechanical behaviour and durability performance. Interface mechanical properties are affected by properties of both the contacting soil and opposing interface. Therefore, a robust understanding of soil-interface behaviour is essential for geotechnical designs. The interface behaviour is characterized by the formation of a wall shear zone with a certain thickness in the soil adjacent to the structure, i.e. a thin zone of intense shearing with both pronounced grain & J. Tejchman [email protected] A. Grabowski [email protected] M. Nitka [email protected] 1
rotations and volume changes. The determination of the thickness of the wall shear zone is of major importance for estimating the shear resistance and forces transferred from the surrounding soil to the structure, resulting in evaluating of the structure strength. The thickness of a wall shear zone depends on several factors such as wall roughness and stiffness, initial density and mean grain diameter of soil and shearing velocity [49, 53, 55]. In problems involving the interface behaviour, Coulomb’s friction law is usually used, based on the assumption of a constant ratio between the shea
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