Research on Multiscale Simulation Methods for Thermal Response of Cemented Sand–Gravel Dams

Numerical Simulation Study of the Permeability Evolution of Sandstone during the Loading and Failure Process Based on FDEM

Rock failure under hydromechanical coupling is a complex process that has attracted considerable attention in deep underground engineering. In this study, a hydraulic coupling analysis method for rock loading and failure is developed based on the finite–discrete-element method (FDEM) combined with the grain-based model, which integrates the dual-medium seepage–stress coupling theory to simultaneously capture pore and fracture seepage. Numerical simulations of sandstone under varying confining pressures were performed and validated against laboratory experiments, and the effects of confining pressure and weak joint content on the permeability evolution were systematically investigated. The results demonstrate that the permeability evolution during loading is governed by the competitive interplay between matrix seepage and fracture seepage, exhibiting a nonlinear pattern. Higher confining pressures prolong the stage of slow permeability growth, whereas an increase in the weak joint content reduces strength and stiffness, leading to an earlier occurrence of the permeability inflection point and an enhanced dominance of fracture flow in controlling macroscopic permeability. These findings provide new insights into the mechanisms of hydromechanical coupling in fractured porous rocks and offer theoretical support for predicting and controlling hydraulic hazards in deep rock engineering.

Multi-Scale modeling of the interface behavior between steel micro piles during wetting-drying cycles

The performance of steel micro-piles in expansive soils is the result of a complex soil-pile interaction that degrades significantly during cyclic wetting and drying. In many cases, traditional macroscopic models do not account for the principles of interface softening and gap formation, which result from microstructural changes in the soil matrix. This paper introduces a Multi-Scale model which puts together micro scale particle interactions and macro scale structural response. In this study, we used the Discrete Element Method (DEM) to look at micro-level clay particle behavior and their interaction with steel surfaces, using the Finite Element Method (FEM) for the large-scale pile and soil system. The model includes variation in matrix suction, which causes swelling and shrinkage. The tests showed that after five wetting and drying cycles, the interface shear strength went down as much as 45%, which resulted from the growth of permanent microcracks and particle rearrangement. Proposed is a multi-scale approach, which we present as a robust solution for the design of micro pile foundations in climate-sensitive regions, and it puts forth what single-scale analysis doesn’t. This multi-scale approach we put forth is for the development of sustainable infrastructure, which prevents us from overdesigning in climate-sensitive areas. Results present that value in adding microstructural information, which, in turn, we note that, by use of it, we can reduce steel resources by 15 to 20% and also report a large drop in the project’s carbon output, which also supports development of what are more resilient and green geotechnical solutions.

Modelling of the Thermo-Hydro-Mechanical Response of Bridge Pile Foundation–Soil System to Degrading Permafrost

Rheological Modeling and Numerical Simulation of Annular Flow of a Drilling Mud Based on Local Materials: Theoretical Parametric Study

Environmentally friendly drilling fluids based on locally available materials represent a promising alternative to conventional formulations. This study investigates the potential use of kaolinitic clay from Brazzaville (Republic of the Congo), okra (Abelmoschus esculentus L.) mucilage, and plant ashes as components of a bio‐based drilling mud. A theoretical and numerical framework was developed to simulate the annular flow of these non‐Newtonian fluids using the Bingham and power‐law rheological models. Analytical solutions were combined with finite‐volume simulations implemented in MATLAB to evaluate velocity profiles and pressure losses under representative drilling conditions. The results show that yield‐stress fluids develop a central plug region that can improve drill cuttings transport, whereas shear‐thinning behavior significantly reduces pressure losses compared with a Newtonian fluid while maintaining favorable flow characteristics. The numerical predictions are in excellent agreement with the analytical solutions, demonstrating the reliability of the proposed model. The main contribution of this work is the development of a modeling framework specifically adapted to drilling muds formulated from locally available Congolese materials, providing a basis for future rheological measurements and experimental validation. This study supports the development of sustainable and low‐cost drilling fluids for petroleum and geothermal applications.

Experimental–Numerical Analysis of the Ultimate Lateral Capacity of PHC Piles

This study investigates the ultimate lateral behavior of prestressed high-strength concrete (PHC) piles in layered ground conditions at a thermal power plant site in Nhon Trach, Vietnam. Full-scale free-head lateral load tests were conducted on single PHC piles with diameters of 300, 400, and 500 mm, and the measured load–displacement responses were used to calibrate a three-dimensional finite element model in Plaxis 3D. The calibrated model reproduced the experimental H–u curves with good agreement and was further used to examine the effects of soil stratification and head boundary conditions. Comparison with the Japanese Road Association (JRA) analytical approach shows that JRA provides conservative displacement predictions for the larger-diameter piles (D400–D500) over practical displacement ranges, while the agreement improves for D300 at larger deformations, reflecting the stronger influence of the underlying soft clay and the limitations of equivalent-soil idealizations in layered profiles. Normalized head displacements at maximum test loads fall within u/D≈0.06–0.13, consistent in order of magnitude with reported full-scale lateral pile tests in the literature. The results support using JRA for rapid screening, whereas calibrated 3D numerical analysis is recommended for working design and for translating free-head test outcomes to fixed-head or pile-group boundary conditions in similar layered ground settings.

Numerical investigation for evaluating seepage and stability of zoned embankment dam