Discrete element method simulations of bio-cemented sands

Abstract

Microbially induced calcite precipitation (MICP) has emerged as a novel soil improvement method. In this paper, 3-D discrete element method (DEM) simulations are used to explore the behavior of MICP-cemented sands. Comparisons of the macro-scale response of numerical and physical specimens are made. Microstructure analyses indicate a shear band formed in the numerical specimens, consistent with physical experiments. The bond breakage pattern in numerical specimens is explored and compared to observed measurements from physical specimens. The relationship between dilatancy and stress-strain behavior is evaluated. The results indicate DEM is an effective technique to capture the mechanical behavior of MICP-cemented sand.

Research on Simulation Analysis Method of Microbial Cemented Sand Based on Discrete Element Method

“…In this study, the same strategy was followed with the same values of elastic module and stiffness ratio parameters being assigned to the particle model and bonding model, respectively. When determining the elastic modules (i.e., E * and E * ) of the MCS material, reference was made to both the previous PFC study on cemented sand column [6] and the indoor elastic module testing results obtained by Porter [28] (sand particle > calcite > calcite-sand Advances in Materials Science and Engineering particle). Finally, the following values were assigned to the elastic module parameters for different material components: for sand particle, E * � E * � 1.50 GPa; for calcite particle, E * � E * � 1.25 GPa; and for calcite-sand particle, E * � E * � 0.85 GPa.…”

“…Among all three bonds, the sand particle-sand particle bond has the lowest strength but the highest discrete level. erefore, for the sand particle-calcite and calcite-calcite bonds, λ is assigned with a fixed value of 0.5 because these bonds are relatively strong according to SEM analysis based on the previous PFC study on microbial cemented sand column by Feng [6]. For the sand particlesand particle bond, a random number was introduced to vary the parallel bond radial coefficient λ between 0.25 and 0.5. e pb ten and pb coh parameters of the MCS material were determined by setting up the initial values according to previous studies by Ali et al [32] and Xue et al [33].…”

“…e linear component describes the elastic relationship between the contact force and the relative displacement of the adjacent entities, which can be used to express the rigidity characteristics of MCS material, whereas the bonding component defines the physical connection at the interface of adjacent entities and can be used to simulate the cementation characteristics of the MCS material [21]. Moreover, the LPBM has been successfully used to explore the mechanical behaviour of MCS material [6]. As such, the linear parallel bonding model was adopted to simulate the bonding behaviour between sand particle-sand particle, sand particle-calcite, and calcitecalcite contacts.…”

“…Wang [5] analysed the mechanical characteristics of artificial cemented sand from which the strong mechanical strength of cemented sand was attributed to the formation of stable force chains in the material structure. Feng [6,7] developed a discrete element model to characterize cemented sands and analysed their mechanical behaviour considering the effect of particle bonding and particle shape. All these studies provide valuable guidelines for developing a numerical simulation model for microbialinduced cemented materials.…”

Editorial

“…Much of the recent work related to MICP utilizes ureolytic soil bacteria to increase the alkalinity of the subsurface and induce calcium carbonate precipitation (Mortensen et al, 2011). The precipitated calcium carbonate in turn improves the strength, stiffness, and dilative tendencies of the soil (Feng et al, 2017;Montoya and DeJong, 2015). The transformation of these soil properties leads to improved behavior under a variety of conditions, including dynamic loading (Montoya et al, 2013).…”