ABSTRACT Based on full-scale field static load tests in sandy/silty clay, this study compares the bearing and deformation characteristics of pile-tip post-grouted bored piles with different length-to-diameter ratios (L/D = 33.3 and 48.0). Both types of piles behave as friction piles. The small L/D piles (short length, large diameter) exhibit better load-bearing performance and smaller settlement under the same load. Their axial force attenuates more slowly, and the mobilization of pile side frictional resistance in the upper and lower parts of the pile is more coordinated, allowing load transfer to deeper soils. In contrast, pile side frictional resistance of the large L/D piles (long length, small diameter) softens in some soil layers. For the same soil type at different burial depths, the pile-soil relative displacement required to mobilize limiting pile side frictional resistance for the same pile varies.

ABSTRACT High-speed rail (HSR) development in India, with trains operating at ~320 km/h on elevated viaducts, demands reliable and indigenous foundation design solutions. Pile groups are widely adopted to enhance bearing capacity and control settlement; however, post-construction settlement under repeated train loading remains insufficiently explored. This study presents a methodology to predict cumulative settlement of pile groups subjected to high-frequency cyclic loading from HSR. A three-dimensional finite element model of the pile group is developed in Abaqus using suitable constitutive model. The influence of train speed, spcing of the pile (S) soil stifness (Es), length of pile (L) and pile cap thickness is investigated. Results indicate that train velocity has minimal impact on ultimate settlement, while increased pile length and stiffness significantly reduce it. The study proposes optimal pile group configurations and provides practical nomograms for efficient settlement prediction of a pile group from single pile settlement for HSR.

ABSTRACT This study examines the uplift load-carrying capacity of vertical piles embedded in granular soils, focusing on developing and validating analytical models using the horizontal slice limit equilibrium approach. Experimental pile tests were employed to empirically determine the inclination angle of the failure surface, which was then incorporated into the model to enhance its accuracy. The research investigates how soil parameters and pile geometry influence shaft resistance and the position of the failure surface. Results reveal that the inclination angle of the failure plane increases with the angle of shearing resistance in sand, leading to steeper, more vertical failure surfaces under uplift loading in stronger soils. The analytical predictions showed consistent agreement with experimental and published data, confirming the reliability of the proposed models. These findings underscore the importance of jointly considering soil strength, pile geometry, and failure surface orientation when predicting uplift shaft resistance in granular soils.

ABSTRACT To address low sensor survival rates and external errors in monitoring the Qinghai-Tibet Highway, this study proposes an inverse method to derive pavement temperatures from stable subsurface thermal data within the roadbed. Validated at a test site, the method showed excellent agreement. It was applied to six representative sections to analyse spatio-temporal characteristics. Results revealed significant regional variations: maximum pavement temperatures followed a ‘high-low-high-medium-high’ pattern from north to south, ranging from 13.52°C to 21.79°C, while minimums ranged from −12.31°C to −7.70°C. High temperatures peaked in June–July, and lows in January. The study emphasizes that regional pavement temperature variations must be considered in permafrost highway thermal stability assessments. This method provides a reliable alternative for data acquisition in harsh environments.

ABSTRACT Debris flows are a significant natural hazard in mountainous regions, posing threats to both humans lives and infrastructure, especially in the context of increasing extreme weather events due to climate change. This study focuses on the Upper Svaneti region of Georgia, where steep slopes and high seasonal rainfall make debris flows a growing concern. The research combines the use of two well-established numerical models, TRIGRS (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability) and RAMMS (Rapid Mass Movement Simulation), to simulate both the initiation and post-failure dynamics of debris flows. A combination of high-resolution UAV-derived topographic data, laboratory-tested soil samples, and historical rainfall records was used to parameterize and validate numerical simulations. The TRIGRS model was first employed to identify unstable slopes triggered by rainfall infiltration, considering saturated soil conditions. Subsequently, RAMMS was used to simulate the flow dynamics and deposition patterns of mobilized material. A back-analysis of the 2022 event using post-event UAV data showed good agreement with observed detachment and deposition zones, though underestimation in deposit height was noted. This confirms the reliability of the model in identifying susceptible areas under critical rainfall thresholds. A reactivation scenario was modelled based on the current terrain configuration, indicating potential downstream hazards even under moderate rainfall, especially if residual or deposited materials are remobilized. Finally, TRIGRS was used to estimate the minimum cumulative rainfall threshold required to initiate failure in the remaining deposits. The results of cumulative rainfall simulations indicated a threshold over 7 days which could trigger failure in the deposition zone. These findings provide key input for hazard mitigation, early warning systems, and regional planning strategies.

ABSTRACT To address land demands from coastal urbanization, dredged sediments are increasingly utilized as landfill materials, consolidated by vacuum preloading (VP) with prefabricated vertical drains (PVD). While VP is well-established for conventional soft soils, the performance differential between PVD types in ultra-soft hydraulic fills remains poorly quantified which is characterized by high water content and fine-grained sediments (d50=0.005mm). This study evaluates VP efficiency usingPVD-A and PVD-B in 3,000 m² reclaimed plots over 160 days. Comprehensive monitoring tracked pore water pressure, surface settlement(SS), layered settlement, water content, and vane shear strength(VSS). Results demonstrated PVD-A’s superior performance, with greater SS, higher VSS, larger PWP reduction, lower consolidation degree, and higher water content. This improved performance may be attributed to PVD-A’s lower longitudinal discharge capacity, which reduced fine particle migration and clogging during early consolidation stages, thereby sustaining drainage efficiency long-term.These findings of PVD-A’s advantage are valuable for optimizing VP design in reclamation projects.

ABSTRACT Bentonite, renowned for its absorption and swelling, is widely used as a drilling fluid. Its particle size distribution (PSD) significantly affects infiltration and filter cake formation, yet research frequently omits essential details like testing conditions, equipment, and concentration. To provide a comparative analysis, the PSD of commercial bentonites (Colclay D90 and IBECO S) was evaluated under dry, wet, and hydrated conditions. Hydrated bentonite prepared with high-speed mixing and hydration showed the smallest particle sizes, followed closely by sonication-dispersed wet bentonite, and then dry bentonite. The d85 differences between hydrated and dry states were substantial: 76.56 μm for Colclay and 136.07 μm for IBECO. Interestingly, Colclay had smaller dry particles but larger hydrated ones compared to IBECO. This study revealed there is no ‘real’ particle size for field slurries, as high concentrations increase PSD while mixing and shear stress may reduce it, emphasizing the importance of clearly describing PSD measurement methods.

ABSTRACT This study introduces a hydro-mechanically coupled elasto-plastic model for unsaturated soils, including hydraulic hysteresis. The model focuses on the isotropic compression behaviour, requiring only three additional model parameters for the hydraulic part, which are determined with a single unsaturated triaxial test. This makes the proposed model significantly more practical while maintaining the desired level of accuracy. The formulation is developed, including the coupling terms that relate the change in water content to net stress and, in turn, the change in void ratio to water retention behaviour. An explicit scheme is utilized in integrating the formulation, where several unsaturated triaxial tests are simulated under various net stress and suction paths. Verification analyses show that the proposed model can capture the coupled response of unsaturated soils more effectively and consistently.

ABSTRACT V s This study focuses on examining the presence of different artefacts in dispersion images generated using the multichannel analysis of surface waves (MASW) technique. The selection of spurious modes (artefacts), while performing the inversion, induces errors in the obtained shear wave velocity profile. The objective is to determine the correct modal curves in the dispersion images by avoiding the spurious modes. ω − c ω c The mathematical analysis reveals that the dispersion image may get contaminated with spurious/dummy modes on account of numerical and physical anomalies. This finding has been demonstrated by doing a comprehensive analysis of both synthetic and actual field data, by taking a few examples, for both types of artefacts. It is concluded that the numerical artefacts may still prevail in dispersion images, on the other hand, the physical artefacts can be eliminated by the proper selection of array spacing. The current research will certainly help in identifying and eliminating the possible numerical artefacts while performing the inversion.

ABSTRACT Pile driving causes the generation of excess pore pressures in the ground, the dissipation of which could take weeks to several months. Permeable pipe pile is proposed as a novel measure to introduce drainage channels at the locations of peak pore pressures around the pile circumference. Five centrifuge tests were designed to underscore the contribution of drainage holes in the consolidation mechanism of the ground and the bearing behaviour of pile foundation subjected to axial loading. Results indicated that the inclusion of drainage holes can help to accelerate the dissipation of pore pressures due to a higher local hydraulic gradient near the pile–soil interface for permeable pipe pile, but it cannot affect the ultimate bearing capacity much. Higher pore pressures were generated for single pile foundation in the ground with a higher undrained shear strength, as well as for pile group foundation. The bearing capacity of pile group was smaller than the combined values of all individual piles due to the pile group effect. It is suggested to apply permeable pipe pile to minimize the set-up effect and enhance the strength gain at an early stage of consolidation.