Creep of granular soils is frequently accompanied by grain breakage. Stress corrosion-driven grain breakage offers a micromechanically based explanation for granular creep. This study incorporates that concept into a new model based on the discrete-element method (DEM) to simulate creep in sands. The model aims for conceptual simplicity, computational efficiency and ease of calibration. To this end a new form of normalised Charles power law is incorporated into a DEM model for rough-crushable sands based on the particle splitting technique. The model is implemented using a controlled on–off computational strategy. The model is validated by simulating creep in quartz sands in oedometric and triaxial conditions. Model predictions are shown to compare favourably with experimental results in terms of creep strain, creep strain rates and particle breakage. The model proposed would facilitate the calibration of phenomenological continuum models, but may also be useful to directly investigate structural scale phenomena, such as pile ageing.@en

Stress relaxation of quartz sands is simulated using a recently proposed physically based time-to-fracture discrete element method framework. The framework incorporates time-dependency through stress-corrosion-induced grain fracture. This feature is embedded into a pre-existing particle-splitting-based rough-contact crushable model. The model is calibrated to represent Fontainebleau sand, a quartz sand. A controlled on–off computational strategy is adopted to advance the simulation efficiently. Model predictions are shown to compare favourably with laboratory results in oedometric and triaxial conditions in terms of stress relaxation and relaxation rate. Grain size distribution evolution is also tracked and shown to compare well with available laboratory results. The influence of initial mobilized strength q/qmax on stress relaxation is recovered by the model, and explained through increased grain breakage. The simulated relaxation results are examined at the microscale and compared with those from creep experiments. The model displays the nonisochronous behaviour characteristic of sands. The relaxation tests display a state shift towards higher dilatancy conditions that may offer a possible explanation for some observations of pile set-up.@en

In situ soil characterization often involves penetration tests. The response to both static and dynamic penetration in volcanic sands is known to be controlled by particle crushing, obscuring the effect of density and confinement on the response. This severely limits the use of penetration tests for soil characterization. In this work a virtual calibration chamber (VCC) built using the discrete element method (DEM) is employed to explore the relationship between cone penetration tests CPTs (static) and standard penetration tests SPTs (dynamic) results on a volcanic sand. The simulated CPT results are shown to capture well experiments from the literature over a range of density and confining stress. The comparison between the simulated CPT and SPT results shows good agreement with empirical expressions based on particle size. It was found that energy-based equivalent dynamic tip resistance obtained from the SPT is a good match for static cone tip resistance if shaft resistance effects are discounted. The results presented confirm the potential of DEM based VCC to examine the performance of in-situ tests in complex soil conditions.@en

Stress relaxation of quartz sand is simulated using a recently proposed physically based time-to-fracture discrete element method (DEM) framework. The relaxation of stress on sands under high confining pressure is modelled using stress-corrosion induced grain fracture. This feature is embedded into a pre-existing particle-splitting based rough crushable model for Fontainebleau sand. A controlled on-off computational strategy is adopted to advance the simulation. The computed oedometer stress relaxation curve compares favourably with previous experimental results. Triaxial stress relaxation results indicate that stress relaxation increases linearly with time. Contact forces become more homogenous during stress relaxation; as a result, the sample becomes more stable. These microscopic behaviours agree with some observations in pile ageing, suggesting that the model may be adopted directly to investigate such engineering scale phenomena due to its conceptual simplicity, computational efficiency and ease of calibration. @en

Active earth pressure on retaining structures supporting a narrow column of soil cannot be properly analysed using Coulomb's theory. Finite-element limit analysis (FELA) shows that the soil forms multiple failure surfaces if the soil column is sufficiently narrow. This paper proposes a framework for active earth pressure estimation for narrow soils by combining an arched differential element method and a sliding wedge method. The analytical framework considers both soil friction and cohesion, soil arching effects and shear stress between adjacent differential elements. The solution obtained is validated against experimental data and FELA results. Through parametric studies, the effects on the active earth pressure of the aspect ratio, soil friction, soil cohesion and wall-soil interface roughness are examined. To facilitate the use of the proposed framework in design, a modified active earth pressure coefficient and an application height of active thrust are provided.

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A contact model able to capture creep of crushable sands within a discrete element method (DEM) framework is presented. Time dependency is established through stress-corrosion induced grain fracture. This is grafted onto a pre-existing particle-splitting model developed to simulate rough-crushable sands. The model is calibrated for Fontainebleau sand and applied to simulate soil creep at high-confining pressures. Creep simulation is advanced using the off-DEM ageing technique. The crackvelocity evolution in particle scale and laboratory oedometer creep curve were successfully captured. Moreover, the onset of creep failure during triaxial creep curve under high deviatoric stress can also be simulated using this model. The results obtained indicate significant potential of this model for micromechanically based investigation of time-dependent soil behaviour.@en

A recently proposed DEM model for materials with rough crushable grains (Zhang et al. 2021; Ciantia et al. 2015; Otsubo et al. 2017) is here employed to examine the effect of contact roughness on the critical state line, a property of granular materials which is a) fundamental for the evaluation of liquefaction risk and liquefied responses and b) easily accessible through DEM simulation (Ciantia et al. 2019).@en