This study presents experimental results from scale model tests on laterally loaded bridge pile foundations in soils subjected to seasonal freezing. A refined finite-element model (FEM) was established and calibrated based on data obtained from the experiments. Furthermore, the model was utilized to investigate the impact of soil scouring depth on the lateral behavior of bridge pile foundations embedded in seasonally frozen soils. The findings indicate that soil freezing significantly enhances the lateral bearing capacity of the pile-soil interaction (PSI) system while reducing lateral deflection of the pile foundation. However, soil freezing results in increased damage to the pile foundation and upward movement of the plastic zone toward the ground surface. Under unfrozen conditions, significant plastic deformations occur on the ground surface and even inside the piles due to the extrusion effect. Additionally, increasing soil scouring depth significantly reduces the lateral bearing capacity of the PSI system while also increasing lateral deflection of the pile foundation for a given load level. Notably, when the scouring depth exceeds 2 m in unfrozen soils, the entire pile experiences obvious deformation and inclination, exhibiting a short-pile behavior that negatively affects the lateral stability of the pile under lateral loads.

This paper employs three-dimensional parallel finite elements to assess the seismic response and resilience of various pile group configurations. The numerical model was verified in the literature through two large-scale shaking table tests. A parametric study was conducted to depict the influences of pile number (N), position within a pile group, pile nonlinearity, and frequency content on the seismic response in sloping liquefiable soils. The result showed that the importance of these factors on the analysis and design for the pile groups, while they are not considered in the current design codes including Japan Road Association (JRA) 2002 and American Petroleum Institute (API). Furthermore, the API method most likely underestimates P-y at shallow depths rather than numerical analysis results, while it overestimates at deeper burial depths. In addition, JRA code overestimates the monotonic soil pressure in the infinite pile group and underestimates it in the finite pile group. In other words, the difference between the computed soil pressure from JRA and the numerical model decreases with N. The asymmetry ratio (AR) is also important for the acceleration response, since AR decreases with N. Also, it has been shown that the seismic responses increase in corner piles with the N due to the increasing stiffness. Subsidence at the downslope side of the pile group and heave at the upslope side of the one occurs and increases with N. Nonlinear pile behavior increases maximum displacements, especially in central piles, while reducing internal forces in corner piles. Corner and side piles yield earlier, requiring middle piles to sustain greater forces under continued lateral spreading.

The overconsolidation ratio considerably affects the physical and mechanical properties of soil as well as the interaction between structures and soil. Scale and consolidation time limitations render the preparation of overconsolidated soil for small-scale model tests difficult. Therefore, studying structure-soil interactions, especially the vertical bearing capacity of pile foundations in overconsolidated soil becomes challenging. Given the importance of reliable overconsolidated soil in physical model tests for studying soil-structure interactions, this study, based on the fundamental of the overconsolidation ratio, established a reliable method for preparing overconsolidated soil by altering centrifuge acceleration. Piezocone penetration tests were conducted to validate the accuracy of this method. Furthermore, vertical bearing capacity of pile foundations was evaluated in various overconsolidated soils. The vertical ultimate bearing capacity of pile foundations, cone penetration resistance, pore water pressure, and sleeve friction resistance were obtained in soils with various overconsolidation ratios. Based on the results of both tests, a formula was developed to calculate the vertical ultimate bearing capacity of pile foundations, taking into account the overconsolidation ratio of soil. This proposed method for evaluating vertical bearing capacity of pile foundations in overconsolidated soil can also be applied to study interactions between other marine structures and soil. The results of the study can provide technical support for designing the foundations of offshore oil and gas facilities, wind power, and other structures.

Experimental evidence indicates that multidimensional cyclic loading of soils causes larger accumulation of deformations than equivalent one-dimensional loading. The response of sand to high-cyclic loading with 10,000 cycles and up to four-dimensional stress paths (i.e., four independent oscillating components) is examined in 120 triaxial and hollow cylinder tests in this work to extend these findings. With increasing number of oscillating stress components, the accumulation of permanent strains tends to increase. It is demonstrated that the definition of the multidimensional strain amplitude incorporated in the high-cycle accumulation (HCA) model can account for this. The validation of the HCA model for complex cyclic loading is complemented by the simulation of model tests on monopile foundations of offshore wind turbines subjected to multidirectional cyclic loading, for which the consideration of spatially variable cyclic loading with nonconstant load amplitudes in the HCA model is discussed. For this purpose, an extension of the HCA model considering multiple strain amplitudes is presented.

The research aims to investigate and compare the seismic responses of various models, including free field, pile group, fixed base, and shallow/deep foundation-structure with different structural height-to-width ratios (h/b) in saturated and dry sands during realistic earthquakes with varying intensities to ascertain whether soilfoundation-structure-interaction (SFSI) has beneficial or detrimental effects. To date, no comparative research has considered the response of shallow and deep foundations in both saturated and dry soil simultaneously. This study addresses this gap using 3D non-linear parallel finite element models validated with two distinct sets of centrifuge tests, and the extended analysis of nonlinearity effects of seismic SFSI considering large deformation performed. Focusing on the time-frequency content distribution result, the input acceleration amplitudes at different times are intensified by passing through the stiffer system (e.g., dry site, remediated soil, and shorter structure) at high frequencies. Conversely, they decrease in a softer system, especially in liquefiable soil, due to the excess pore pressure build-up. The time of PGA alters at the foundation level, and correspondingly, the commencement time of significant settlement occurs quicker or later. A structure with a more flexible base exhibits greater rocking and a reduction in flexural drifts, internal forces, and base shear force to seismic weight ratio. This subsequently results in a decrease in the local damage sustained by the structure. In contrast to lower h/b, the structural base shear force in the saturated soil site is greater than in the dry one, due to the higher peak structural acceleration.

Most structures supporting solar panels are found on thin-walled metal piles partially driven into the ground, optimizing costs and construction time. These pile foundations are subjected to repetitive lateral loads from various external forces, such as wind, which can compromise the integrity of the pile-soil system. Given that the expected operational lifespan of photovoltaic solar plants is generally 20-30 years, predicting their service life under fatigue loads is crucial. This research analyzes the response of H- piles to lateral fatigue loads in cohesive rigid soils through four field tests, subjected to load cycles of 55%, 72%, and 77% of the static failure load, corresponding to maximum loads of 25 kN, 32 kN, and 35 kN, respectively. Additionally, the effect of load cycles on the degradation of pile-soil adhesion is studied through two pull-out tests following cyclic tests. This study reveals that soil fatigue does not occur under repetitive loads and that soil stiffness remains constant once the cycles causing soil compaction have been overcome. Nevertheless, the accumulated plastic deflection of the soil increases steadily once soil compaction occurs due to cyclic loading. The implications of these results on the fatigue life of photovoltaic solar panel foundations are discussed.

Flooding occurrences have become increasingly severe, posing a serious danger to end-user safety and bridge resilience. As flood fragility assessment is a valuable tool for promoting the resilience of bridges to climate change, it is of great importance to push the development of such methods. However, flood fragility has not received as much attention as seismic fragility despite the significant amount of damage and costs resulting from flood hazards. There has been little effort to estimate the flood fragility of bridges considering various flood-related factors and the corresponding failure modes. To this end, a fragility-based approach that can explicitly address the scour-hole geometry and flood-induced lateral load is presented. First, a three-dimensional finite-element model with pile foundations and surrounding soil was established to estimate the failure mode under various flood scenarios. The loadings on pile foundations were characterized by vertical loading from the superstructure, horizontal loading from the flood-induced lateral load, and the scour effect simulated through a time-history analysis. Then, all potential failure modes of bridge pile foundations in various flood scenarios were summarized. Based on extensive parameter investigations using the deterministic method, the dominant failure mode of penetration failure was determined, and a failure envelope was fitted to guide the design of the pile foundation. Upon establishing the failure mode, a probabilistic fragility analysis considering uncertainties in hydraulic, structural, and geological parameters was finally conducted using the Latin hypercube sampling (LHS) method. The results showed the effects of variation on the fragility of the pile foundation, highlighting that the deterministic analysis without considering the uncertainties in model parameters leads to underestimating the risk due to the penetration failure and the significant influence region.

Fastening of hydrotechnical oil-gas mining facilities to seabed soils in Caspian Sea aquatoriums is usually carried out by pile foundations. Sustainability of strength and stability during the design and construction of hydraulic structures requires to solve a number of theoretical and practical problems. Numerous static and dynamic tests (experiments) were carried out in the Caspian Sea aquatorium and in laboratory conditions to solve these issues. The widespread use of pile foundations in the development of offshore oil and gas fields revealed the inconsistency of the domestic scientific methodological and regulatory framework for calculating their load-bearing capacity over the soil. It is established that the wave strikes, acting on pile foundations, interact with the surface design of offshore structures and offshore ground bases. Sea wave banging pile foundations creates vibrations in the pile foundation - topsides offshore structures and moving piles in subgrade. Displacement piles depend on the strength of the reaction between the structure and subgrade, the intensity of the shock wave in the time that passed through piles for offshore soil. At the same time, it takes into account the rheological properties of composite models of shelf soil.