The newly developed three-dimensional finite element program was applied to the problem of the stress and deformation of the reclaimed marine deposits for the connecting bridge at the corner of the Kansai International Airport (KIX) fill. The connecting bridge of KIX is supported by the sea friction piles and the abutment on the airport fill. Differential deformation has been expected to occur at the border of the pile foundation and abutment on the reclaimed fill. Then, for the corner of the large reclaimed island, a three-dimensional analysis is strongly required because a stress dispersion with depth for the applied filling load is expected to occur, and one and two-dimensional approaches have a definite limitation to assess the stress and deformation due to reclamation. Stress dispersion was remarkable with depth. The stress concentration effect due to the existence of a deeply compacted sand column in the alluvial clay layer influenced the subsequent deformation of the Pleistocene deposits. Remarkable lateral displacement, as a typical three-dimensional behavior, was observed in association with long-term settlement. It is noteworthy that the in-situ measured settlement is found to be well described with the calculated performance by the developed 3D elasto-viscoplastic finite element program.

Highly organic soils are often challenging for geotechnical applications due to their low strength, high compressibility, and increased permeability. This study investigates the efficacy of xanthan gum (XG) biopolymer as an ecofriendly alternative to traditional, carbon-intensive soil stabilizers. A comprehensive series of laboratory experiments was conducted to assess the effects of XG on the compaction behavior, unconfined compressive strength (UCS), elastic modulus (E₅₀), and permeability of organic soils. XG dosages ranged from 0% to 5% (by dry weight of soil), with aging periods extending up to 60 days. The test results demonstrate that 1% XG significantly improves the mechanical properties of the soil, achieving a sixfold increase in UCS and E₅₀ greater than 20,000 kPa within 28 days of aging. Additionally, permeability was reduced by 3-5 orders of magnitude, meeting the stringent requirements for hydraulic barrier applications. Scanning electron microscopy (SEM) identified the formation of a bridging gel matrix and associated pore-clogging as the key microstructural mechanisms responsible for the significant gains in strength and the drastic reduction in permeability. Based on the analysis of strength, stiffness, and permeability, 1% XG was identified as the optimal dosage. These findings highlight the significant potential of XG as a sustainable, cost-effective solution for stabilizing highly organic soils, offering substantial performance enhancement while maintaining environmental benefits. XG presents a viable alternative to conventional stabilizers in geotechnical applications, particularly in projects requiring environmentally conscious and efficient material solutions.

In highway engineering, foamed concrete used for subgrade filler is typically influenced by external environmental factors such as freeze-thaw cycles and vehicle loads. This study conducts freeze-thaw cycle tests, load cycle tests, and coupling (freeze-thaw-load) cycle tests under the designed wet density to simulate the field environment of highway engineering and examine the strength variation of foamed concrete under different conditions. Additionally, the pore structure and freezing damage mechanism of foamed concrete were analyzed using SEM. The results indicate that the strength loss of foamed concrete exceeds 20% after 100 freeze-thaw cycles. During the load cycle tests, the compressive strength of foamed concrete can be divided into three stages, corresponding to the development of micro-cracks in the material. In the coupled environment to simulate field conditions, the compressive strength of foamed concrete decreases rapidly to 0.96 MPa (20.66% loss) after the first 10 years, which followed by a slower decline (0.83 MPa in the 20th years and 0.78 MPa in the 40th years). SEM analysis shows that the internal damage caused by freeze-thaw cycles can be categorized into cavity failure and crack failure.

The hyperbolic method is a method of predicting the future settlement from the measured settlement based on the assumption that the speed of settlement decreases in the form of a hyperbola over time. However, this method forces artificial linearity during linear regression analysis because both the independent variable (time) and dependent variables (time/settlement) contain time. Thus, to overcome this problem, this study proposed the nonlinear and weighted nonlinear regression hyperbolic methods to supplement the statistical incompleteness of the original hyperbolic method based on linear regression. A hyperbolic method that applied nonlinear regression analysis and a weighted nonlinear regression hyperbolic method that applied high weight linearly over time were proposed as alternatives to the existing linear regression hyperbolic method. The accuracies of the original, nonlinear, and weighted nonlinear regression hyperbolic methods were analyzed and compared based on the time-settlement data measured from six sites with thick soft clay layers in Busan New Port. The proposed methods yielded superior results compared to the original hyperbolic method. Further research on the forms of various weight functions can lead to the formulation of an optimal weighted nonlinear regression hyperbolic method.

The conventional uniformity coefficient C_u fails to capture the uniformity of gap-graded granular mixtures. To address this limitation, this study introduces a new index C_u^m for quantifying mixture uniformity based on their small-strain stiffness G₀. Granular mixtures with varying fines content (FC) and particle size ratio (PSR) were prepared, and their G₀ values were determined through quasistatic drained triaxial tests. The corresponding C_u^m values were then derived from the measured G₀ values and expressed as a function of FC and PSR. The rationality of the proposed C_u^m was verified, and it was further demonstrated that C_u^m can be used to predict the small-strain stiffness of granular mixtures when the mechanical coordination number (CN_m), particle shear modulus of particles (G_p), confining stress (σ₀) and C_u^m are known.

Particle breakage can alter the gradation of soil, reduce the interparticle contact friction induced by shear, and serve as a primary cause of deformation in geomaterials, significantly influencing their engineering mechanical properties. The single-particle crushing test is an essential test method for investigating particle breakage and strength. However, merely analyzing particle strength neglects the deformation information during the crushing process, leading to an inability to accurately characterize the strain state before the particle's overall breakage. In this study, single-particle crushing tests were designed and conducted to analyze the particle strength and specific fracture energy of limestone particles. Based on the analytical results, an equivalent stiffness was formulated. By introducing the concept of equivalent stiffness, the distribution of specific fracture energy was transformed into a particle strength distribution. The validity and reliability of this conversion method were verified, demonstrating its effectiveness in statistically characterizing different stress-path features of particles. This study reveals that the equivalent stiffness of 10-20 mm Baihetan limestone particles in single-particle crushing test is 4.7×10⁶N/m. This result offers a reference value for associated numerical modeling and can inform the corresponding engineering design.