Drying of tailings in sections of tailings-based earth structures, such as tailings dams, often leads to structural defects particularly tensile cracking which can undermine stability. Understanding and mitigating these phenomena require accurate modeling of the yielding behavior of these materials under unsaturated conditions. However, this critical aspect has garnered limited attention in the existing literature. To address this knowledge gap, a comprehensive experimental program was conducted, including micromechanical analyses using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). Additionally, strain-controlled and different stress-path triaxial tests were performed on reconstituted tailings samples collected from the Sungun copper mine, under low relative compaction, isotropic and anisotropic confinement, and various matric suction levels. Microstructural investigations revealed that macropores progressively decreased with increasing consolidation stresses, influencing both the soil–water characteristic curve (SWCC) and the unsaturated yielding response. Yield points obtained from stress-path triaxial tests were evaluated against existing models, which exhibited limited predictive accuracy. After modifying the yield formulation of ABBM1—a stress-based anisotropic model—the corrected version successfully reproduced the experimental yielding points with significantly improved accuracy (RE = 5.3
Permeation grouting is an effective technique for mitigating seepage and soil instability in underground engineering, achieved by reinforcing soil layers and sealing water inrush pathways. Polymer-based grouting materials, owing to their rapid solidification and high permeability, have been widely applied; however, the resulting grouted sand exhibits complex and heterogeneous microstructural characteristics. To elucidate the spatial distribution of micropore structures in grouted sand, constant flow (CF) and constant pressure (CP) grouting experiments were conducted under different hydraulic heads (H) and mass fractal dimensions ( D_m ). The evolution of microstructures was characterized through mercury intrusion porosimetry, scanning electron microscopy, and X-ray diffraction. Furthermore, the pore size distributions at different spatial positions were correlated with the unconfined compressive strength (UCS). The results demonstrated that: (1) CF mode produced a more uniform pore distribution compared with CP mode. Within 20 cm of the injection port, porosity downstream was significantly lower than that upstream, and the location of minimum porosity was shifted downstream. (2) Lower porosity indicated better consolidation. Overall porosity decreased with increasing D_m , whereas both excessively high and low H values hindered slurry diffusion and consolidation. A moderate H promoted the formation of low porosity grouted sand. (3) During failure, cracks predominantly propagated through large pore regions with weak polymer–sand bonding. X-ray diffraction analysis showed that no new mineral phases were detected, suggesting that the consolidation mechanism was governed primarily by physical filling and interfacial bonding. (4) A negative correlation was observed between porosity and UCS. CF mode showed advantages in both strength enhancement and overall water-blocking performance, although both modes maintained high water-blocking ratios after grouting.
The substantial waste muck generated by slurry pressure balance (SPB) shield tunneling presents considerable economic and environmental challenges in its disposal. This study proposes a waste-reuse-oriented approach for developing a backfill grouting material using shield waste muck and an industrial waste-based cementitious binder (IWBCB). Waste muck at two water contents was solidified using IWBCB, followed by performance tests assessing fluidity, 2-h bleeding ratio, 28-day shrinkage rate, and compressive strength. The solidification mechanisms were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results show that (1) a favorable formulation involves preparing a slurry with a water content of 55
This study presents a constitutive framework for modeling the stress–strain response with solid–fluid instability (static liquefaction) in saturated granular materials using the disturbed state concept (DSC), incorporating a coupled disturbance function dependents on both plastic deviatoric and volumetric strains. Static liquefaction is characterized by a sudden drop of shear strength due to pore pressure buildup, leading to excessive plastic deformation and abrupt failure. The peak strain ratio indicates the onset of instability, consistent with Lade’s theory, and highlights the role of plastic volumetric strain in contributing to material disturbance. The DSC offers a comprehensive approach by treating soil as a heterogeneous, evolving material. However, its conventional formulation defines disturbance evolution exclusively in terms of plastic distortional (deviatoric) strain, limiting its capability to capture the effects of volumetric changes that drive pore pressure buildup and trigger static liquefaction under undrained conditions. To address this limitation, a coupled disturbance function is proposed that incorporates plastic volumetric effects, contributing to the instability and deformation associated with static liquefaction phenomena. The model is validated with published triaxial experimental results, confirming its versatility in capturing the response of saturated sands across varying effective confining pressures and initial relative densities. The critical hardening modulus, as defined by Hill’s instability criterion for predicting static liquefaction, is influenced by evolution of disturbance. Moreover, the predicted results show that the proposed disturbance function with DSC based model enhances the accuracy of stress–strain response predictions and, with critical hardening modulus and second-order work criteria, accurately predicts the onset of static liquefaction, which coincides with peak deviatoric stress.
Accurate prediction of spudcan bearing capacity and the associated soil stress distribution is critical for the safe installation of jack-up offshore platforms. The bearing capacity is commonly evaluated using small-strain finite element methods (FEM); however, due to the conical geometry of spudcans, severe element distortion may occur. This can lead to artificial stress concentrations near the spudcan tip, resulting in unrealistic stress fields and biased capacity estimates. This paper proposes an implicit elastoplastic finite-deformation framework incorporating a skew-boundary interface formulation to overcome mesh distortion and eliminate spurious stress concentrations. In the proposed approach, both the mesh and geometry are continuously updated during deformation, enabling a consistent representation of large soil deformation without the use of artificial viscosity or rate-dependent regularization. Structural components are modeled as linear elastic, while soil behavior is described using the Mohr–Coulomb yield criterion. Model performance is first validated through comparison of bearing capacity factors for wedge-shaped footings with apex angles ranging from 30° to 150° against published solutions. The method is subsequently applied to spudcans with fully open cavities embedded in soil. The results demonstrate that the proposed formulation effectively mitigates spurious stress concentration and yields physically consistent stress distributions and bearing capacity predictions over a wide range of embedment depths.
