Soils and Foundations最新文献

Cohesive soils in nature are created under anisotropic stress and have various stress histories. Embankments generate greater vertical loads underground. Moreover, associated excavation activities can exacerbate the extensional stress state. This study investigated the effects of induced anisotropy on the shear modulus in saturated and unsaturated cohesive soils. A triaxial testing apparatus, equipped with local small strain (LSS) measurement devices and bender elements (BEs), was used to measure the small strain shear modulus. Two series of tests were conducted: (1) LSS and BE tests used specimens normally consolidated under a constant mean effective stress of p’ = 300 kPa or net mean stress p_net = 300 kPa with different stress ratios to investigate the effects of anisotropic consolidation. The values of the applied stress ratios, represented as K = σ'_h/ σ'_v for the saturated soil and K_net = (σ_h–u_a)/(σ_v–u_a) for the unsaturated soil, were 0.35, 0.43, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, and 3.5. (2) BE tests used specimens consolidated under various mean effective stresses in the order of p’ = 50, 100, 200, 300, 400, 500, and 600 kPa, and swollen in reverse order under K of 0.35, 0.43, 0.6, and 1.0, to elucidate p’ and the effects of the overconsolidation ratio (OCR). The results demonstrated that K-consolidation under constant p’ produces large differences in initial shear modulus G₀ in saturated cohesive soil, but K_net produces only slight differences in unsaturated cohesive soil because of the influence of strong matric suction. Finally, G₀ was normalized successfully considering the effects of void ratio e, K, and OCR.

In response to the significant earthquakes that struck Turkey and Syria on February 6, 2023, a collaborative reconnaissance team, consisting of researchers and engineers from Japan and Turkey, was formed by the Japan Association for Earthquake Engineering, the Architectural Institute of Japan, the Japan Society of Civil Engineers, and the Japanese Geotechnical Society. This coalition conducted an in-depth on-site investigation from March 28 to April 2, two months after the catastrophic seismic events. In Islahiye, a landslide resulted in the formation of a landslide dam. Another landslide occurred in Tepehan on a relatively gentle slope formed of limestone, with possible correlations to fault movements. Iskenderun encountered not just building collapses on soft ground, but also instances of the tilting of buildings and ground subsidence attributed to the liquefaction of reclaimed coastal soil. Golbasi witnessed significant liquefaction-induced damage to structures with shallow foundations on soft ground, involving tilting and settling. However, a more comprehensive investigation is required to accurately map the extent of the liquefied soil layers. Antakya and Kahramanmaras emerged as regions where building damage coincided with surface ground vibrations. Despite severe building collapses, Antakya's relatively stable ground showed an average S-wave velocity exceeding AVS30 400 m/s. This suggests potential wave amplification due to underlying geological structures. Kahramanmaras displayed notable building damage concentrated in alluvial fan formations.

Soil-water characteristic curve (SWCC) and coefficient of permeability (k) are amongst the most crucial soil properties in unsaturated soil mechanics for soil moisture conservation. The direct measurement and prediction of such properties are important to engineering applications, but they are complicated. This study developed a new experimental setup (the OT permeameter) using osmotic tensiometers (OTs) and the continuous evaporation method. The proposed OT permeameter could directly measure SWCC and k up to 1000 kPa suction within one to two weeks. Moreover, the proposed setup is fully automated and data processing was minimal. In addition, a new general equation has been developed to predict and best fit the unsaturated k measurement. The proposed equation uses a minimal number of parameters that carry physical meaning and provides an intuitive and easy way to predict and best-fit k measurement. The accuracy and robustness of both the proposed OT permeameter and prediction equation were evaluated using published data and experimental data from this study.

This paper elucidates the challenges and opportunities inherent in integrating data-driven methodologies into geotechnics, drawing inspiration from the success of materials informatics. Highlighting the intricacies of soil complexity, heterogeneity, and the lack of comprehensive data, the discussion underscores the pressing need for community-driven database initiatives and open science movements. By leveraging the transformative power of deep learning, particularly in feature extraction from high-dimensional data and the potential of transfer learning, we envision a paradigm shift towards a more collaborative and innovative geotechnics field. The paper concludes with a forward-looking stance, emphasizing the revolutionary potential brought about by advanced computational tools like large language models in reshaping geotechnics informatics.

Volcanic pumice, with special characteristics such as crushable particles and high water retention, is distributed throughout Japan and serves as the source layer for slope hazards characterised by post-failure gentle slope flows and long-distance flows. The aim of this study is to determine the relationship between the crushing characteristics and the mechanical properties of porous pumice, which often contributes to such disasters. As the porous pumice material, Ta-d pumice, which caused numerous slope disasters during the 2018 Hokkaido Eastern Iburi Earthquake in Japan, was collected and subjected to a series of triaxial compression tests. The grain size distribution of the pumice before all the tests was adjusted to be uniform, and the amount of crushing was quantified by measuring the grain size distribution after the tests. The results suggest that the critical state and isotropic consolidation of porous pumice can be systematically expressed in a three-dimensional space with the axes of the void ratio, mean effective stress, and degree of particle crushing. Furthermore, a gentle slope disaster with an inclination of less than 21°, that had occurred at the site from which the Ta-d pumice was collected, was discussed in terms of its flow potential, showing that the flow distance can be adequately explained.

An analytical solution is developed to investigate the model of simplifying the pile-soil interaction to a spring-damping system when the horizontal earthquake input or the top of the model is subjected to horizontal dynamic load. Based on Euler-Bernoulli theory, the dynamic equilibrium equations of pile in soil and air are established, respectively. Then, utilizing the corresponding boundary conditions, potential function decomposition, and transfer matrix method, the analytical expression of impedance at the pile head whether the horizontal earthquake input or the top of the system is subjected to horizontal dynamic load can be presented. Furthermore, the model of the pile-soil complex interaction can be simplified as a spring-damping system according to the stress equilibrium at the pile bottom in the air. Moreover, the rationality of the present solution (without simplification) is verified by comparison with existing methods, and then the difference between the present solution (without simplification) and the spring-damping system (simplification) is also compared. Finally, the influence of the parameter variation in the pile buried in the soil and soil free-field on the simplified model are discussed. The research results will be instructive for the simplification of numerical model for pile-soil interaction.

Soil frost deformation significantly influences engineering projects in cold regions. The anisotropic behavior of soil, involving surface and internal deformation in three dimensions (3D), introduces inaccuracies in evaluating freeze–thaw geological hazards. To explore the relationship between internal strain and surface displacement of soil in a 3D space during the freezing-thawing process, a platform for monitoring coupled surface-internal deformation in 3D were developed using binocular recognition technology and a novel 3D strain rosette. Subsequently, a freezing-thawing model test of soil in Dalian Offshore Airport filling is conducted using the platform. The results show that, the internal strain of soil is closely associated with the boundary conditions of the test unit. During freezing test, the vertical strain exhibits a more significant increase in comparison to the horizontal strain. Surface displacements in soil primarily occur during the initial freezing and thawing stages. The variation of surface horizontal displacement in each direction is minimal throughout the freezing-thawing process. A surface freezing boundary leads to an increment in internal strain, while the deep frozen stress relief causes the soil surface expand during thawing. This study provides a suggestion for the control of the cold source in cold region engineering.

Fully liquefied soils behave like viscous fluids, and models developed within the framework of soil mechanics fail to catch their behaviour on the verge of liquefaction or after it. Several research works have shown that modelling the liquefied soil as a fluid is physically more convincing. Such an equivalent fluid can be characterised via an apparent viscosity (η) (sharply dropping when liquefaction is triggered) which can be modelled as a power law function of the shear strain rate (pseudo-plastic fluid), depending on two parameters: the fluid consistency coefficient (k) and the liquidity index (n). With this approach, it is possible to consider a simple correlation between the equivalent viscosity and pore pressure increments independent on the equivalent number of cycles, whose parameters can be calibrated from the results of stress-controlled laboratory tests. The paper investigates the effect of some relevant experimental factors (effective vertical stress, stress path, frequency and waveform of the applied cyclic load, soil fabric and pre-existing shear stress) on the apparent viscosity of soils during their transition from the solid to the liquefied state, and therefore also on the pore pressure increments generated by the stress path. To do that, the results of stress-controlled laboratory tests performed in a sophisticated simple shear apparatus, along with published data, have been interpreted in terms of the apparent viscosity. Simple correlations in terms of viscosity-based pore pressure generation and pseudo-plastic behaviour are proposed and confirmed from the results of 1D non-linear site response analysis for the case study of Scortichino (Italy).

Dynamic soil-structure interaction (SSI) significantly impacts structural vibration. Over the past few decades, numerous simplified models were developed to analyze dynamic SSI on homogeneous soil. In this study, however, a lumped-parameter model is adopted to investigate the dynamic behavior of rectangular foundations overlying nonuniform soil. The simplified three-parameter model is utilized to analyze the torsional vibration of rectangular foundations on layered soil with linearly varying shear-wave velocities. Non-dimensional parameters (shear-wave velocity ratios, layer depth ratios, and mass ratios) are also investigated herein. The frequency-magnification curves of the foundation using three-parameter model are found to agree well with theoretical solutions. Consistent agreements are also observed at the resonant response and its corresponding frequency ratio. Additionally, the resultant resonant magnification factors against mass ratios clearly show the impacts of the whipping effect resulting from soil-foundation interactions. The proposed model excels in simulating layered soil and includes fewer parameters than existing lumped-parameter models. The proposed model also demonstrates the adaptivity and reliability to simulate the dynamic responses calculated from the published in-situ experimental data. The time-domain application based on the proposed model effectively estimates the structural displacement of the soil-foundation-superstructure system. This research could contribute to the SSI analysis regarding the torsional vibration of a foundation on nonuniform soil.

The construction of steel pipe piles combined with side grouting is regarded as an effective way to improve the uplift bearing capacity of piles for transmission towers in rugged mountainous areas. This new piling technology involves the injection of grout into the annular space between the steel pipe pile and the side boundary of the pre-dug hole, which aims to improve the properties of soil-pile interface. However, to date, there are few studies on the soil-pile interface property and uplift failure model of this new kind of steel pipe piles with side grouting. In this study, the shear properties of the grouting interface between soil and steel plate were investigated, and then compared with the shear tests of undisturbed plastic clay and gravel clayey soil. It is indicated that the shear strength of the grouting interface between soil and steel plate is less than that of corresponding undisturbed soils. In addition, the uplift loading test about two grouted implantation steel pipe piles (GISPP) instrumented with Fiber Bragg Grating (FBG) sensors in plastic clay and gravel clayey soil was carried out, which demonstrates that the failure surface of GISPP mainly occurs in the interface of soil and grouting body. The grouting body can be well bonded to the steel pipe pile after uplift, but the ground surface around the GISPP presents a conical failure model. Finally, a new method considering the conical failure model was proposed to calculate the ultimate uplift capacity of GISPP, which was validated to be efficient and reliable compared with previous calculation methods.