A novel discrete element method (DEM) model is proposed to better reproduce the behaviour of porous soft rocks. With the final goal of simulating pile penetration problems efficiency and scalability are two underlining features. The contact model is based on the macro-element theory and employs damage laws to govern the plastic deformations developing at the microscale. To attain (i) high porosity states, (ii) represent irregular shaped grains and (iii) incorporate the physical presence of bond fragments, the model is cast within a far-field interaction framework allowing for non-overlapping particles to transmit forces. After presenting a calibration procedure, the model is used to replicate the behaviour of Maastricht calcarenite. In particular, the mechanical response of this calcarenite is explored within the critical state theory framework. Finally, the efficiency, performance and scalability of the model is tested by simulating physical model experiments of cone-ended penetration tests in Maastricht calcarenite from the literature. To boost efficiency of the 3D numerical simulations, a coupled DEM-FDM (Finite Differential Method) framework is used. The good fit between the experimental and numerical results suggest that the new model can be used to unveil microscopic mechanism controlling the macroscopic response of soft-rock/structure interaction problems.

The displacements and deformations of buildings with separated footings caused by tunneling may be significant and could damage the structures. This paper numerically investigates the influences of building stiffness, geometry, and foundation pressure on the deformation of a two-story elastic framed building due to tunneling in sand. An advanced soil constitutive model known as hypoplastic model was calibrated and adopted to simulate the sand behavior. Results show that the roles of building stiffness and foundation pressure on the footing displacements due to tunneling are significant, particularly for a larger tunnel volume loss. An increase in building stiffness reduces both the vertical and horizontal displacements of footings, while a greater foundation pressure primarily increases footing settlements. The influences of building stiffness and foundation pressure on building shear distortion are considerable, while their impacts on panel horizontal strains are minor for the investigated parameter ranges. The results also suggest the potential use of greenfield results as a conservative estimation of the distortion of buildings with separated, embedded footings when subjected to tunneling-induced displacements. Modification factors for shear distortion and horizontal strains are presented and show good agreement with the empirical centrifuge-derived envelopes for buildings resting on the soil surface.

Cyclic loading of deep foundations and soil anchorage elements can lead to failure by accumulation of deformations or loss of strength. Snakeskin-inspired surfaces have been shown to mobilize direction-dependent friction angles and volumetric responses due to their asymmetric profile. This paper presents an investigation on the cyclic interface element behavior of sand-structure interfaces with snakeskin-inspired surfaces with the goal of understanding the potential impact of these surfaces on the cyclic behavior of geotechnical elements. Load- and displacement-controlled cyclic interface shear tests were performed with constant stiffness boundary conditions. Four different snakeskin-inspired surfaces and reference rough and smooth surfaces were tested. The results show that under symmetric shear stress cycles, failure always takes place in the caudal direction (i.e. along the scales) due to the smaller interface friction angles. A shear stress bias can produce a change in the failure direction to the cranial one (i.e., against the scales). An equation is introduced to predict the magnitude of shear stress bias that changes the failure direction. This investigation shows that the snakeskin-inspired surfaces can be used to control the direction of failure of soil-structure interface elements which can help in increasing the cyclic stability and reducing the susceptibility of brittle failure.

By conducting a two-dimensional experimental study, this paper aims to enhance the understanding of the mechanism of sand convective motions in the vicinity of a wall subjected to long-term cyclic lateral loadings. The experimental tests were conducted in a rectangular sandbox with a transparent front -wall, through which the process of sand particle motions could be recorded by using a high -resolution digital camera. The images were processed with a high time -resolved PIV (Particle Image Velocimetry) system. Based on the experimental data, this work (1) presents the sand flow field in the convective zones; (2) provides means to describe the convection mechanism; (3) proposes the relationships between the loading conditions and dimensions of the region with intense sand movement; and (4) elaborates the similarity of the sand flow velocity structure within the sand convective zones.