Large-diameter drilled shafts show rotational-behavior under lateral loads inducing pressure on pile base, which may affect the lateral load capacity. This study examines the effect of pile base pressure (pbase) to the lateral load capacity of large-diameter drilled shafts in sand. A series of centrifuge tests were conducted on model piles with varying slenderness ratios (L/D) and soil conditions, where pbase was directly measured. The lateral load–displacement responses, bending moments (BM), and pbase distributions were systematically analyzed. Test results revealed that pbase was asymmetrically distributed across the pile base and played a non-negligible role in the overall lateral resistance. The values of BM mobilized at the pile base (BMb) were evaluated to quantify the effect of pbase. The contribution of BMb to total BM (BMt) increased with decreasing L/D and increasing pile stiffness, particularly in loose sands. At the ultimate limit state (ULS), percent ratio of BMb/BMt ranged from 3.6% to 15.0%, while it reached up to 25.7% at the serviceability limit state (SLS). Based on these results, a modification factor to quantify the contribution of BMb to the lateral load capacity was proposed with the goal of establishing a more robust and optimized design strategy for drilled shafts.
Embankment widening over soft ground can produce severe differential deformation because the preconsolidated foundation beneath the existing embankment interacts with the relatively weak ground beneath the widened section. This study examines how this inherited stiffness heterogeneity and the spatial extent of column reinforcement control deformation compatibility in geosynthetic-reinforced column-supported (GRCS) embankment widening. A numerical model framework incorporating preconsolidation-induced foundation zoning, different column spacings, and alternative reinforcement extents is developed. The analyses identify two characteristic responses: an interface-localized deformation mode associated with an abrupt stiffness transition and a system-distributed mode promoted by extending column reinforcement beneath the existing embankment. For the evaluated configurations, full reinforcement overlap reduced maximum settlement by approximately 62.1% relative to the unreinforced heterogeneous case. Increasing column spacing from 1.5D to 3D increases settlement from 36.5 mm to 42.9 mm, whereas a spacing range of 2–2.5D provides an effective balance between deformation control and construction cost. A dimensionless Stiffness Continuity Index (SCI) is introduced to quantify the relative stiffness of the existing and widened foundation zones, with SCI = 1 representing stiffness matching. The framework further shows how a target SCI can be translated into preliminary column replacement ratio, spacing, and reinforcement extent. SCI, therefore, complements conventional settlement and stability checks by providing a compatibility-based approach to transition-zone design.
Analytical solutions are derived for the coupled thermo-hydro-mechanical (THM) response of a saturated porous layer of finite thickness subjected to a disk-shaped thermal loading on its surface, with the thermo-osmosis and mechano-caloric effects retained. The layer is confined by a smooth, rigid, impermeable, and thermally insulated base, while its upper surface is drained, traction-free and heated locally, a boundary-value problem different from the classical half-space solutions. Unlike the half-space formulation, which retains only the decaying exponentials, the present solution, obtained in the Laplace-Hankel transform domain, retains both growing and decaying exponential branches that are coupled through hyperbolic functions of the layer thickness by the eight boundary conditions. The half-space solution is recovered only as the layer thickness approaches infinity, and the finite-layer response converges to it only when the thickness exceeds five loading radii. Compared with the pore-pressure regime predicted by the half-space solution, blocked drainage in the base causes the thermo-osmotically driven downward flux to accumulate within the layer, and the peak pore pressure is 9.1–11.2% higher at a thermo-osmosis ratio of 106 Pa·K−1. Accordingly, the tensile-failure risk shifts to the bottom of the layer rather than concentrating at depth. The solution further reveals deformation patterns not reported for half-space models: a settlement ring between one and two loading radii that migrates outward as heat penetrates, and the maximum horizontal expansion at the loading periphery. These findings indicate that the integrity assessment of finite-thickness low-permeability barriers, such as nuclear-waste buffers and landfill liners, should be based on finite-layer models including thermo-osmosis.
Although environmental moisture conditions strongly affect gas–solid carbonation, supplied air relative humidity (RH) effect on the CO2 fixation ability of fly ashes with different water retention characteristics has not been investigated yet. To address this issue, constant-flow aeration type CO2 fixation tests were conducted under different supplied air RH conditions using three fly ashes (FC, MF, and BBF) in this study. The CO2 fixation ability was evaluated based on CO2 fixation amount and the reaction rate per unit dry mass. The main findings are summarized as follows: 1) For all three fly ashes, CO2 fixation was low under low RH conditions, suggesting the limitation from insufficient interfacial water; 2) for FC and BBF, higher RH conditions increased CO2 fixation ability. However, MF, which had higher chloride content and higher water retention, exhibited reduced CO2 fixation ability under high RH conditions, likely because excessive water accumulation reduced the pore space available for gas flow and impeded CO2 transport; and 3) the suitable inlet RH depended on the material-specific water retention characteristics under the tested specimen and flow conditions.
This study presents a novel quantitative approach to investigate the microstructural response of cohesive soils to a single freeze–thaw (FT) cycle in both open (with water migration) and closed (without migration) freezing systems. This topic has been scarcely explored in previous research. The aim was to determine how different freezing systems affect pore geometry and to identify the key microstructural parameters driving these changes. Soils were analyzed using a combination of Numerical Image Analysis (NIA), Factor Analysis (FA), and MANOVA, providing a comprehensive assessment of microstructural alterations after one FT cycle in both systems. The results demonstrate that soil texture governs freeze–thaw sensitivity, and that the microstructural response depends on the interaction between soil type and freezing system. Open systems induce larger and more heterogeneous changes, whereas closed systems lead to more uniform modifications, with porosity identified as the most responsive microstructural parameter. The major factors controlling variability shifted from pore shape descriptors to geometric parameters, highlighting the critical role of microstructure in cohesive soil behavior and offering new insights into structure–property relationships in natural materials.
