This study presents a hierarchical multiscale approach that combines the finite-element method (FEM) and the discrete-element method (DEM) to investigate tunneling-induced ground responses in coarse-grained soils. The approach considers both particle-scale physical characteristics and engineering-scale boundary value problems (BVPs) simultaneously, accurately reproducing typical tunneling-induced mechanical responses in coarsegrained soils, including soil arching and ground movement characteristics observed in laboratory tests and engineering practice. The study also unveils particle-scale mechanisms responsible for the evolution of soil arching through the underlying DEM-based RVEs. The results show that the rearrangement of microstructures and the deflection of strong contact force chains drive the rotation of macroscopic principal stress and the formation of soil arch. The microscopic fabric anisotropy direction can serve as a quantitative indicator for characterizing soil arching zones. Moreover, the effects of particle size distributions (PSD) and soil densities on ground deformation patterns are interpreted based on the stress-strain responses and contact network characteristics of DEM RVEs. These multiscale insights enrich the knowledge of tunneling-induced ground responses and the same approach can be applied to other geotechnical engineering analyses in coarse-grained soils.

A novel framework for nonlinear thermal elastic-viscoplastic (TEVP) constitutive relationships was proposed in this study, incorporating three distinct thermoplasticity mechanisms. These four TEVP formulations, combined with an existing TEVP constitutive equation presented in the companion paper, were integrated into a coupled consolidation and heat transfer (CHT) numerical model. The CHT model accounts for large strain, soil selfweight, creep strains, thermal-induced strains, the relative velocity of fluid and solid phases, varying hydraulic conductivity and compressibility during consolidation process, time-dependent loading, and heat transfer, including thermal conduction, thermo-mechanical dispersion, and advection. The performance of CHT model, incorporating different TEVP constitutive equations, was evaluated through comparing the simulation results with measurements from laboratory oedometer tests. Simulation results, including settlement, excess pore pressure and temperature profiles, showed good agreement with the experimental data. All four TEVP constitutive relationships produced identical results for the consolidation behavior of soil that in the oedometer tests. The TEVP constitutive equations may not have a significant effect on the heat transfer in soil layers because of the identical performance on simulating soil compression. The CHT model, incorporating the four TEVP constitutive equations, was then used to investigate the long-term consolidation and heat transfer behavior of a four layer soil stratum under seasonally cyclic thermal loading in a field test, with excellent agreement observed between simulated results and measured data.

Discrete element modeling (DEM) is a useful tool for linking global responses of granular materials to underlying particle-level interactions. A DEM model capable of capturing realistic soil behavior must be calibrated to a reference dataset, typically consisting of laboratory experiments. Calibration of a DEM model often requires numerous simulations as contact parameters need to be iterated upon until the simulation results satisfactorily replicate the experimentally observed behaviors. This paper presents a sensitivity investigation that examines the effects of the contact parameters on the drained triaxial compression response of a poorly-graded sand. It then introduces a calibration procedure capable of providing contact parameters that satisfactorily reproduce the results of laboratory triaxial results in a few simulations. Results show that friction and rolling resistance coefficients jointly influence the mobilized peak and critical state friction angles, secant shear modulus, maximum dilation rate, total volumetric strain, and strain softening magnitude. These parameters also influence the mode of failure at contacts and the evolution of fabric anisotropy. The influence of mu r or mu on the triaxial response and particle-level interactions is coupled, becoming more profound as the other parameter is increased. Contact stiffness is shown to influence the shear modulus and volumetric change behavior independently of mu and mu r. An algorithm that estimates values for mu and mu r needed to reproduce experimental results is developed using triaxial response parameters from experimental datasets. The performance of the proposed calibration method is demonstrated for three natural sands showing that it provides appropriate calibrated parameters for poorly graded sands with different relative densities and confined with varying effective stress magnitudes.

Soil-steel composite bridges (SSCBs) are commonly utilized as overpasses. In the majority of existing studies, the transverse structural performance of SSCBs is primarily focused on, while neglecting their longitudinal structural performance. The aims of this paper are to clarify the longitudinal properties and compensate for the paucity of research on the longitudinal structural performance of SSCBs. In current study, field tests were conducted on a SSCB case bridge in a mining area, both in the construction stage and post-construction stage. Subsequently, longitudinal differences in the structural settlements, deformations, and hoop strains were analyzed. Additionally, a refined three-dimensional finite element model was developed and verified to analyze the transfer behavior of soil pressure above the structure along the longitudinal direction. The results indicate that in the construction stage, the difference in the soil-covered height primarily account for the differences in structural performances along the longitudinal direction. At the end of backfilling, the settlements, deformations, and hoop strains in the middle are all greater than those in the end sections. In the post-construction stage, further developments of longitudinal structural characteristics occur due to creep deformation of the foundation soil and disturbances from mining trucks. One year after construction, the structural characteristics have stabilized. The maximum settlement reaches -1.014 m and the maximum settlement difference reaches 0.365 m. The differential settlement ratio, at 0.62 %, remains within the 1 % limit specified in the CHBDC code. Due to longitudinal settlement differences, the soil pressure in the higher settlement zone is transferred to the lower settlement zone by the longitudinal soil arching effect, which benefits the load-bearing capacity of SSCBs.

Lignin fiber is a type of green reinforcing material that can effectively enhance the physical and mechanical properties of sandy soil when mixed into it. In this study, the changes in the dynamic elastic modulus and damping ratio of lignin-fiber-reinforced sandy soil were investigated through vibratory triaxial tests at different lignin fiber content (FC), perimeter pressures and consolidation ratios. The research results showed that FC has a stronger effect on the dynamic elastic modulus and damping ratio at the same cyclic dynamic stress ratio (CSR); with the increase in FC, the dynamic elastic modulus and damping ratio increase and then decrease, showing a pattern of change of the law. Moreover, perimeter pressure has a positive effect on the dynamic elastic modulus, which can be increased by 81.22-130.60 %, while the effect on the damping ratio is slight. The increase in consolidation ratio increases the dynamic elastic modulus by 10.89-30.86 % and the damping ratio by 38.24-100.44 %. Based on the Shen Zhujiang dynamic model, a modified model considering the effect of lignin fiber content FC was established, and the modified model was experimentally verified to have a broader application scope with a maximum error of 5.36 %. This study provides a theoretical basis for the dynamic analysis and engineering applications of lignin-fiber-reinforced sandy soil.

Tunneling-induced horizontal strains for buildings with discontinuous foundations are notable and may pose significant risks to the integrity of nearby structures. This paper presents results from a series of numerical models investigating the response of framed buildings on separated footings to tunnel construction in sand. The study examines a two-story, elastic frame with varying building transverse width, eccentricity, and first story height, subjected to tunneling-induced displacements; footing embedment depth and tunnel cover depth are also varied. Results show that tunneling-induced horizontal displacements for separated footings are significant, with greater footing horizontal displacements occurring at deeper footing embedment depths. Building width and eccentricity also influence soil-footing interaction, particularly in determining the values of footing displacements and the distribution of horizontal strains. An increase in footing embedment depth slightly increases shear distortion but significantly increases horizontal strains. The presented modification factors for angular distortion and horizontal strains align well with empirical envelopes, with the horizontal strain modification factor being sensitive to the relative soil-footing stiffness. This research highlights the importance of considering horizontal strains and realistic foundation embedment depth in the damage assessment for buildings with discontinuous foundations due to tunnel construction.

This study evaluates the dynamic behavior of a subsea railway tunnel during an earthquake, considering ground conditions and seismic wave characteristics using the finite difference modeling method. A comprehensive ground-tunnel structure system model was constructed to analyze the structure's response during earthquakes, yielding significant results. Analysis of lining stress values in the subsea tunnel revealed that the maximum compressive stress in the soil part is significantly larger than in the rock part in composite ground conditions, and the maximum compressive stress in the fractured zone is increased by up to 10 times compared to the rock zone. In addition, a seismic fragility curve for subsea tunnels was derived from a series of analytical results. The analysis indicates that the probability of minor damage exceeds 50 % for earthquakes of about 0.32 g and above, while the probability of moderate damage exceeds 50 % for earthquakes of 0.39 g and above for subsea railway tunnels passing through various ground conditions.

The tetrapod jacket-supported offshore wind turbine is subjected to marine environmental loads, resulting in monotonic and cyclic lateral-compression-tension interaction behavior of the pile-soil system. Although the excellent applicability that has been demonstrated by three-dimensional numerical simulation for aiding the revelation of the mechanism of jacket foundation-soil interaction, a significant challenge remains in accurately reflecting the nonlinear stress-strain relationship and cyclic behavior of the soil, and others. Finite element numerical models are therefore established for laterally loaded tetrapod jacket pile foundations in this study, and a bounding surface model is adopted to simulate the elastoplastic characteristics and cyclic ratchet effect of the soil. Subsequently, a parametric analysis is conducted on different net spacings and aspect ratios of the jacket base-piles to investigate the pile deformation characteristics, bearing mechanisms, evolution of pile-soil interaction, and the internal force development under monotonic and cyclic conditions, respectively. The results indicate that under monotonic loading, the pile deformation pattern transitions from a flexible pile mode to a rigid rotational deformation mode as the aspect ratio decreases. Under cyclic loading, attention should be paid to the asynchronous accumulation of axial forces within the base-piles and its impact on overall bearing performance.

This paper introduces a thermo-hydro-mechanical (THM) framework to model thaw consolidation in permafrost regions. By integrating internal energy degradation functions and a modified Cam-Clay model within a phase-field damage framework, the model focuses on simulating the simultaneous effects of phase change and particle rearrangement. The model integrates two distinct phase-field variables with the modified Cam-Clay plasticity framework. One phase-field variable monitors pore phase composition, while the other captures particle rearrangement. These variables are directly coupled to the constitutive model, providing critical data for updating the stress-strain relationship by accounting for particle rearrangement-induced softening and hardening effects due to volumetric deformation. The model converges to the modified Cam-Clay model when there is no phase change. This approach addresses a significant gap in existing models by capturing the associated microstructural evolution and plastic softening in thaw-sensitive soils. Validation efforts focus on experimental scenarios assessing both the mechanical impacts of thaw consolidation and the dynamics of phase transitions, particularly emphasizing latent heat effects. The results demonstrate the proposing model's capability of handling complex behaviors of permafrost under thaw conditions, confirming its potential for enhancing infrastructure resilience in cold regions.

In this paper a three-dimensional agro-hydrological model for shallow landslides' prediction is presented. The model is an extension of the CRITERIA-3D free-source model for crop development and soil hydrology, developed by the Hydrometeorological service of the Regional Agency for Environmental prevention and Energy of EmiliaRomagna region (Arpae-simc). The soil-water balance is computed through the coupling of surface and subsurface flows in multi-layered soils over areas topographically characterized by Digital Elevation Model (DEM). The rainfall infiltration process is simulated through a three-dimensional version of Richards' equation. Surface runoff, lateral drainage, capillarity rise, soil evaporation and plant transpiration contribute to the computation of the soil hydrology on an hourly basis. The model accepts meteorological hourly records as input data and outputs can be obtained for any time step at any selected depth of the soil profile. Among the outputs, volumetric water content, soil-water potential and the factor of safety of the slope can be selected. The validation of the proposed model has been carried out considering a test slope in Montue` (northern Italy), where a shallow landslide occurred in 2014 a few meters away from a meteorological and soil moisture measurement station. The paper shows the accuracy of the model in predicting the landslide occurrence in response to rainfall both in time and space. Although there are some model limitations, at the slope scale the model results are highly accurate with respect to field data even when the spatial resolution of the Digital Elevation Model is reduced.