Consolidation and settlement of soft soil ground are the main problems encountered for geotechnical engineers, and drainage boundary conditions play a crucial role in consolidation analysis and settlement prediction. Despite some theoretical approaches that have been proposed incorporating some particular drainage boundary conditions, there remains a dearth of rigorous analytical solutions for multilayered soils that effectively capture various drainage boundary conditions. This study presents a novel approach where the spectral method is used to capture the impact that drainage boundary condition has on the consolidation of multilayered soil. The drainage boundary condition over time is considered, while the excess pore water pressure (EPWP) profile across different soil layers can be described as a single expression using matrix operations. This proposed method is then verified with field investigations where the varying drainage condition is captured and compared with other solutions. The results show that the consolidation behavior will be overestimated if the traditional boundary conditions are used and the proposed method can predict the consolidation of soil with greater accuracy and flexibility. EPWP and settlement at different depths can be estimated such that they agree better with the field data, and the study also indicates that there is a noticeable discrepancy in the predicted consolidation when the drainage boundary condition is not considered properly.

Particle morphology plays a crucial role in determining the mechanical behavior of granular materials. This paper focused on investigating the effects of boundary conditions on the triaxial mechanical properties of soil samples, with particular consideration given to the influence of particle shape. To achieve this, a numerical model was proposed, which couples the finite difference method (FDM) and the discrete element method (DEM) to simulate the behavior of a rubber membrane and soil particles, respectively. The particle morphology was accurately reconstructed using spherical harmonics (SH) analysis, and the shell cells in the FDM were utilized to construct the boundary modeling. Through a series of simulations, the macroscopic and microscopic mechanical responses of soil particles, both within and outside the shear band, were investigated. The obtained simulation results were then compared with those derived from the DEM simulation using a particle-based membrane. The research findings pertaining to the influence of boundary conditions and particle shape provide significant contributions to our understanding of granular material behavior. These findings offer valuable insights that can be applied in the design and analysis of geotechnical structures.

The interface resistance during installation is crucial for the stability and safety of suction caisson in offshore geotechnical engineering, which is strongly affected by the penetration rate and soil-structure interface mechanical properties. This research conducts a series of clay-structure interface shear tests using modified direct simple shear device to fully study the mechanical behavior of clay-suction caisson interface. The effect of shear rate, over consolidation ratios (OCRs), interface boundary conditions, stress levels, and interface roughness were considered. Results show that as the OCR increases, the strength of both the clay and interface increase but show distinct patterns under constant volume (CV) and constant normal load (CNL) boundary condition. It was found that the interface strength is positively related to interface roughness and shear rate impact both the clay and corresponding interface strength. Under CNL conditions, the strength of normally consolidated (NC) clay decreases with rising shear rate, while the over consolidated (OC) clay demonstrate a opposite trend. In contrast, the effect of shear rate on interface behavior gets complicated owing to the combination of roughness, stress levels, and OCRs. Under CV conditions, the shear strength of clay and interface exhibits a logarithmic growth relationship with shear rates. The result of this work can provide a basis for interface resistance evaluation for suction caisson installation in clay.

Based on the modified simple direct shear device which can directly measure the interface pore pressure and interface shear displacement, a series of interface shear tests and corresponding pure clay shear tests were conducted at an undrained state in constant normal load (CNL) boundary conditions or equivalent undrained state in constant volume (CV) boundary conditions. The clay-structure interfaces, consisting of seabed clay and Speswhite kaolin clay with overconsolidation ratios (OCR) of 1 and 3, were tested at three shear rates, respec-tively V1 = 0.0002 mm/s, V2 = 0.001 mm/s, and V3 = 0.01 mm/s. The results demonstrated that the shear strength of the clay-structure interface is lower than that of pure clay, and this difference is more pronounced under CV boundary conditions. In CNL condition, though the pure clay strength decreases with increasing shear rate at OCR = 1 and increases with increasing shear rate at OCR = 3, the shear rate effect on clay-structure interface strength is not obvious. In CV condition, the strength of the interface with the normally consolidated (NC) and over consolidated (OC) clay increases approximately linearly with the shear rate on the semi -logarithmic scale. the shear rate parameter p is used to describe the growth rate of pure clay or clay-structure interface shear strength with a tenfold increase in shear rate. As for normally consolidated clay, in CV condi-tion, the corresponding shear rate parameter satisfies that p (with R1 roughness)> p (pure clay)> p (with R2 roughness). The rate parameter corresponding to NC seabed clay is significantly higher than the rate parameter corresponding to NC Speswhite kaolin clay. For OC clay, the shear rate parameter for interface strength is higher than that for pure clay, meeting with the relationship that p (with R1 roughness)> p (with R2 roughness)> p (pure clay).

The thermal parameters of adherent layer are of great significance to the distribution characteristics of temperature field and foundation stability control of runway in permafrost region. This paper investigated the effects of annual range of temperature (A), annual average temperature (T-A), and other factors on the adherent layer thickness (H), temperature amplitude (A(0)), and annual average ground temperature (T-0), and further analyzed the thermal parameters of the adherent layer by using the FEM (Finite Element Model) roadbed temperature field and experimental data. The results indicate: A and average monthly total solar radiation (Q) have the most serious on H. A numerical method for determining the parameters of the adherent layer based on various conditions such as A and T-A was proposed by multiple regression. The temperature fields of the three types of pavements obtained by FEM and the experimental data were compared with the numerical calculation results for verification, and the conclusions were in close agreement, illustrating that the proposed method for calculating the parameters of the adherent layer is reasonable and effective. The research results extend the application region of adherent layer theory and provide a reference for runway construction in the permafrost region of Northeast China.

Permafrost thaw due to climate warming modifies hydrological processes by increasing hydrological connectivity between aquifers and surface water bodies and increasing groundwater storage. While previous studies have documented arctic river baseflow increases and changing wetland and lake distributions, the hydrogeological processes leading to these changes remain poorly understood. This study uses a coupled heat and groundwater flow numerical model with dynamic freezing and thawing processes and an improved set of boundary conditions to simulate the impacts of climate warming on permafrost distribution and groundwater discharge to surface water bodies. We show a spatial shift in groundwater discharge from upslope to downslope and a temporal shift with increasing groundwater discharge during the winter season due to the formation of a lateral supra-permafrost talik underlying the active layer. These insights into changing patterns of groundwater discharge help explain observed changes in arctic baseflow and wetland patterns and are important for northern water resources and ecosystem management.