Accurate quantification of pore structures and characterization of pore-scale fluid behavior are fundamental to the modeling of unsaturated flow and multiphase interactions in geotechnical systems. This study presents a computationally efficient Pore Radius Propagation (PRP) approach for estimating pore-size distributions from computed tomography (CT) datasets. The proposed method was validated using open-access in-situ CT images of Hamburg sand and glass-bead specimens subjected to unconfined compression and drainage-imbibition cycles. The PRP approach characterized the microstructural features of both materials and enabled the derivation of corresponding water retention behavior. Furthermore, it successfully captured the spatial evolution of pore structures induced by irregular particle rearrangement and the stochastic formation and collapse of localized pores during uniaxial loading. The proposed framework also accurately reproduced the microscale spatial distribution of capillary water under specified suction conditions, demonstrating its capability to represent pore-scale hydraulic responses. Compared with conventional pore morphology (PM) methods, the PRP approach reduced computational processing time by approximately 16–50%, while maintaining high predictive accuracy. Owing to its computational efficiency and robust representation of pore-scale characteristics, the proposed method provides a reliable basis for automated extraction of microstructural parameters. It offers significant potential for future cross-scale integration with discrete-element-method frameworks.
Follower-embedded plate anchors are advantageous relative to drag-embedded anchors as installation depth is controlled, reducing uncertainty on anchor capacity. After installation the plate is vertical in the seabed, but orientates towards the loading direction as mooring line tension develops. Plate anchor translations and rotations during this ‘keying’ process and during subsequent ‘post-keyed’ environmental loading causes excess pore pressure accumulation in the soil around the anchor. In soils that contract during shearing, this pore pressure generation will reduce soil strength, although over time consolidation leads to subsequent strength increases that increase anchor capacity.This paper introduces an effective stress macro-element model that calculates changes in plate anchor capacity due to excess pore pressure generation and dissipation. The model works iteratively between two calculation modules: (1) a macro-element module that generates the anchor kinematics and anchor resistance, and (2) a critical-state based effective stress framework that calculates accumulated plastic shear strain, from which excess pore pressure, and in turn, effective stress and undrained shear strength is calculated.The merit of this effective-stress macro-element model is demonstrated through comparisons with results from finite element simulations and experiments of plate anchor keying in clay that included pauses during keying to allow for consolidation. The model is shown to capture both the degradation in anchor resistance associated with excess pore-pressure accumulation during anchor keying and also the subsequent recovery in anchor resistance due to consolidation. As also demonstrated by the experiments, the model predicts greater anchor capacities for the longer consolidation durations, highlighting how time-dependent strength evolution can be incorporated to more reliably calculate plate-anchor capacity over the design life of an asset.
The effective thermal conductivity of sand–fines mixtures is controlled by fines content, packing state, pore-fluid conductivity, stress, and the conductivity contrast between particle fractions, yet the particle-scale mechanisms linking these factors to the macroscopic response remain unclear. This study develops a generalized-contact thermal DEM framework for gap-graded mixtures, in which the conductive network includes both real contacts and near-contact particle pairs connected through narrow pore-fluid gaps. Heat-transfer contributions are decomposed into coarse–coarse, coarse–fine, and fine–fine pathways. A generalized-contact structural potential is introduced to characterize the combined effects of particle-pair size, separation, orientation, and network connectivity. At the composition-specific densest states, effective thermal conductivity first increases and then decreases with fines content. The initial increase is driven by improved packing and the development of coarse–fine GC-SFS thermal bridges, whereas the subsequent decrease is associated with the loss of coarse-skeleton continuity and the reduced efficiency of the fines-dominated network. Under low pressure, GC-SFS conduction dominates over real solid–solid contact conduction. Moreover, the thermal network evolves more gradually than the force-chain network because near-contact particle pairs can transfer heat without carrying substantial force. By combining the structural potential with corrections for pore-fluid conductivity, pressure-enhanced contact conduction, and fine-particle conductivity, an explicit predictive model is established. After limited calibration, the model reproduces two published sand–fines datasets with mean absolute percentage errors of 4.66% and 4.68%, demonstrating its potential for mechanism-informed prediction across different mixture conditions.
A nonlinear shaft-plate coupled load transfer model is proposed for axially compressed helical piles. The novelty of the model lies in treating the helix plate as a discrete internal bearing interface embedded within a continuous shaft load transfer system, so that the axial-force jump, displacement compatibility, and nonlinear resistance mobilization are solved simultaneously within a single boundary value problem. Hyperbolic load–displacement relations are adopted for both the distributed shaft resistance and the localized plate bearing, with the initial stiffness parameters ks0 and Kb0 derived from the same elastic continuum solution to ensure internal consistency within a unified framework. Displacement compatibility and axial force jump at each plate location complete the nonlinear boundary value problem, which is solved through an iterative finite-difference scheme updating equivalent secant stiffness until convergence on both plate load and displacement field. The pile head response, axial force distribution, shaft friction mobilization, plate bearing ratio, and interface stiffness degradation are obtained. Parametric studies reveal that pile geometry, helix embedment depth, and soil stiffness gradient collectively govern the nonlinear load transfer characteristics. Within the investigated parameter range, increasing load promotes a progressive redistribution of axial resistance from the shaft toward the helix plate. The extent of this transition depends on the relative shaft-plate strength and stiffness, rather than being a fixed response mode. Both shaft friction mobilization and interface stiffness degradation exhibit a spatially non-monotonic distribution, peaking in a primary transfer zone above the helix plate and diminishing below. This depth-zoning pattern is induced by plate-mediated load diversion and is absent in conventional straight piles.
The shear behavior of rock joints is governed by joint roughness, normal stress, and specimen size. Prior studies characterize roughness with a single index, obscuring the distinct mechanical contributions of waviness and unevenness across varying normal stresses and sizes. This study conducted a systematic program of numerical direct shear simulations to quantify differentiated contributions of waviness and unevenness to shear strength. Equivalent specimens of multiple sizes were generated using a statistical equivalence method constrained by power spectral density, and joint morphology was decomposed into waviness and unevenness through wavelet transform. Results show that the unevenness-related strength component increases linearly with normal stress, whereas the waviness-related strength component shows a decline at normal stresses of 50% and 80% UCS. With coupled increases in normal stress and specimen size, the relative contribution of unevenness to peak shear strength rises progressively and exceeds 94% at 0.3 m under normal stress of 80% UCS, while the relative contribution of waviness correspondingly decreases. The roughness angle associated with waviness exhibits negative size dependence, whereas the unevenness becomes nearly size-invariant at 0.2 m. Microcrack statistics reveal a transition from tensile-dominated cracking at low normal stress to increasingly shear-dominated failure at higher normal stress, whereas energy dissipation remains consistently dominated by shear. These findings provide a controlled numerical basis for interpreting the differentiated contributions of waviness and unevenness.
