Understanding the temperature-dependent behavior of sands is essential for geotechnical engineering applications, especially in environments with long-term temperature variations. This study investigates the effects of temperature (T) on the shear strength and creep deformation (Delta epsilon CP) of KMUTT and Hostun sands through a series of consolidated drained triaxial compression (CDTC) tests. Monotonic loading (ML) and sustained loading (SL) schemes were applied to evaluate shear strength and creep behavior under various stress levels (SL) and temperatures. The temperature effect parameter (Af) was introduced to quantify the reduction in shear strength at elevated T relative to a reference temperature (T0 = 30 degrees C). Experimental results show that shear strength decreases as temperature increases, with Hostun sand being more temperature-sensitive than KMUTT sand. Under SL, significant Delta epsilon CP was observed, increasing with both SL and T, while resumption of shearing after SL did not affect peak shear strength. A hyperbolic empirical equation was developed to predict Delta epsilon CP for a given creep duration (Delta tCP), SL, and T, incorporating temperature effects via Af. The model was validated with experimental results and showed strong predictive capability, especially during the primary creep stage. However, discrepancies appeared at high SL, where secondary creep effects became more pronounced. The proposed model offers a practical framework for predicting long-term creep deformation in sands under temperature variations, enhancing geotechnical design in thermally influenced environments.

Offshore wind turbines (OWTs) are subjected to prolonged external loading, including loads induced by wave action. The soil undergoes bi-directional coupled shear, due to this low-frequency and long-duration loading, the cumulative deformation of the offshore foundation is observed to increase, which poses a threat to the functional reliability of the offshore wind turbines. The soil around the piles is distributed with clay layers. Due to the complex mechanical properties of clay, bi-directional cyclic loading tests are performed to research the drainageinduced deformation characteristics of clays in this paper. Based on these test results, the variation of hysteresis loops of stress-strain, resilient modulus, and the cumulative strain are found to exhibit a strong correlation with both the cyclic stress level and the confining pressure. The stress-strain hysteresis loops and resilient modulus have significantly different trends at higher or lower cyclic stress levels. Then an empirical model that uniformly reflects the strain-hardening and softening characteristics, and an empirical model reflects the characteristics of cumulative strain development in soils is established. Finally, the performance of the permanent cumulative strain prediction model is assessed based on the in-situ test findings from the clay foundation.

The pressuremeter test is a widely used in-situ test method in geotechnical engineering for determining ground properties. It is applicable to all types of soil and weak rocks, it records soil deformation under loading conditions. This paper presents a literature review on the application of the pressuremeter test in evaluating the behavior of foundations under load. It explores the methods used to interpret pressuremeter test data in various soil types, reviews the different analytical models employed, and focuses on approaches for assessing the behavior of foundations using pressuremeter test results. The achievements and limitations of each method are presented and discussed. Despite the extensive literature on the applications, interpretation, and development of the pressuremeter test, its use in evaluating the behavior of foundations under load remains limited. This work seeks to address this research gap by identifying challenges in utilizing pressuremeter test data for such analyses and providing recommendations for future research. This work aims to encourage further investigation into the potential of pressuremeter tests for advancing the understanding of foundation behavior under loading conditions.

The offshore wind turbines (OWT) are subjected to cyclic loads, such as ocean waves and wind, over extended periods. The soil surrounding the pile experiences bi-directional cyclic shear. As a result of the low-frequency and long-term loading in the pile-soil interaction, the cumulative deformation of pile foundation increases, posing a risk to the operational safety of wind turbine system. The soil around the piles is distributed with soft clay and clay layers. To study the cumulative deformation properties of clay under complex stress states. A series of tests are conducted, the variation of resilient modulus under different cyclic stress levels and confining pressures is analyzed based on test results. Then an empirical model uniformly reflecting strain-hardening and strainsoftening properties of clay is proposed. The variations of model parameters are investigated. Then the established empirical model is used to modify the maximum elastoplastic modulus at each unloading within the bounding surface constitutive model, a parameter reflecting the magnitude and rate of strain accumulation is also introduced. This method is characterized by a simple expression and requires fewer model parameters. Finally, the predicted results of modified constitutive model are compared with test results to verify the validity of the established model.

Offshore wind turbines (OWTs) are subjected to long-term cyclic loading, such as wind and wave loading, leading to axial-torsional bidirectional cyclic loading in the pile surrounding soil. This bidirectional cyclic loading results in the cumulative deformation of the pile foundation. The larger cumulative deformation endangers the operational safety of the wind turbine system. In China, offshore wind farms mainly consist of clay layers and their cyclic mechanical characteristics need to be examined. Therefore, a series of bidirectional cyclic loading tests are carried out by using a hollow cylindrical torsional shear apparatus to investigate the effect of different cyclic stress levels on the cumulative strain. The results revealed that cumulative strains stabilize as the cycles increase when the cyclic stress level is less than the critical cyclic stress level. An empirical model based on the test results is developed to reflect the cumulative deformation characteristic. In the bounding surface constitutive model, the plastic modulus interpolation function is improved by using the established empirical model,the effect of loading and unloading routes on the variation of plastic modulus is investigated. Furthermore, a modified constitutive model is used to predict the cumulative deformation of soil under the effect of bidirectional cyclic loading. The predicted results agree well with the findings achieved from the tests.

Long-term cyclic loading applied to clay at stress levels lower than the critical cyclic stress leads to soil deformation without inducing damage. The Monismith model is well-known for its simplicity and ability to describe the trend of cumulative plastic strain under cyclic loading. However, the simulated cumulative plastic strain increases indefinitely with the number of cycles until damage occurs. At lower cyclic stress levels, the cumulative plastic strain tends to be stabilized with an increasing number of cycles, ultimately limits the applicability of the model. To address this issue, a series of axial-torsional bi-directional cyclic loading tests are conducted on saturated clay using a hollow cylinder torsional shear apparatus. An empirical three-parameter mathematical prediction model is proposed by analyzing the development of cumulative generalized shear strain based on test results. The relationships of model parameters a with plasticity index, frequency, generalized shear stress, and mean effective stress; b with plasticity index, and c with frequency and plasticity index are presented as functional expressions. Finally, the predicted results of the empirical model are compared with test results to verify its effectiveness, providing a basis for calculating cumulative deformation in clay under long-term low cyclic stress levels.

Traffic-induced cyclic stresses in the subsoil are three-dimensional, and it is important to acknowledge that cyclic major, intermediate, and minor principal stresses have obvious impacts on the permanent strain of the subsoil. Therefore, a series of cyclic true triaxial tests were performed on intact marine clay to investigate the evolution of permanent major principal strain (epsilon(p)(1)) under long-term true triaxial cyclic loads in this study, considering the effects of the amplitudes of cyclic deviator stress (q(ampl)), coefficient of the cyclic intermediate principal stress (b(cyc)), and the slope of the stress path (eta). The test results indicated that epsilon(p)(1) exhibits an increasing trend with increasing CSR, but decreases nonlinearly with an increase in b(cyc)and eta. This implies that the increasing amplitude of cyclic deviator stress promotes the development of epsilon(p)(1), and the accumulation of epsilon(p)(1) is limited by the growing amplitudes of the cyclic mean principal stress and cyclic intermediate principal stress. Considering the effects of CSR, b(cyc), and eta on epsilon(p)(1), a five-parameter empirical model is established to describe the accumulation of epsilon(p)(1) under true triaxial cyclic loads. In addition, the proposed model is verified by the permanent deformation data in this study and previous studies.

The mechanics of methane hydrate-bearing sediments (MHBS) have been broadly investigated over recent years in the context of methane-gas production or climate-change effects. Their mechanical investigation has mainly been carried out using models constructed from experimental data obtained for laboratory-formed MHBS. Along with the dominant effects of hydrate saturation and morphology within the host soil pores, this study recognizes the effective pressure at which the hydrate is formed as a key factor in the MHBS mechanics. A state-of-the-art experimental study has been conducted in order to isolate the effect of the hydrate formation pressure, for use as a model parameter. Two generalized mechanical prediction models that incorporate the effect of the hydrate formation pressure are developed in this work: (a) an analytical shear strength prediction, and (b) an empiric graphical model for predicting volumetric changes along a given stress path. The models are related to a novel data representation which enables the analysis of a few individual test outcomes as a whole, through a volume-change mapping that describes the complex influence of the volumetric effect of hydrate in MHBS, under combined hydrostatic and deviatoric loading scenarios. In this study, we delve into a specific configuration of hydrate morphology, hydrate saturation, and host soil type, enabling a distinctive fundamental geotechnical investigation and the development of a conceptual modeling approach. The paper describes the approaches by which the MHBS properties can be extracted for other MHBS samples (than those examined in this work) having different host soils and hydrate pore-space morphologies.

The growing popularity of GIS technology in Ethiopia has encouraged multiple scholars to investigate landslide hazards using quantitative approaches, despite its limitations. The present review examined the approach used in the evaluation of landslide hazards by five prior studies that shared catchments. The review results reveal that the controlling factors assumed by the five researchers were inconsistent and resulted in highly divergent frequency ratio (FR) values, even for the same factors. This implies that the contribution of a single instability factor can be inferred sufficiently for landslide hazard assessment and mapping; otherwise, the results are highly subjective and disputable. Since the soil type in the region was alluvial-colluvial in the five studies, and a majority of the failures occurred shortly after rainfall, rainfall data and basic soil properties (classification and shear strength) should not be overlooked. In addition to the nonstandard use of morphometric parameters, the inherent limits of GIS methodologies, the omission of hydrogeotechnical properties, and the observed subjective outcomes make the GIS-based approach imprecise, error-prone, and doubtful. The total effect will result in ineffective early warning systems and unworthy mitigation measures, resulting in significant life costs and damage. As a result, it is recommended that GIS technology should be coupled with software (TRIGRS, Scoops3D, SINMAP, OpenLISEM, GLM, and SLIP) that considers hydrogeotechnical properties to provide more reliable conclusions. In addition to using instability factors consistently, regional statistical correlations of all morphometric parameters can be developed, allowing for less complex and realistic empirical models to be used.

In recent years, several empirical and semiempirical relationships have been proposed to predict the small-strain shear modulus of unsaturated fine-grained soils along different hydraulic and mechanical loadings paths. However, a major deficiency of these relationships is the absence of a coupled linkage between hydraulic and mechanical processes that occur in unsaturated conditions. Specifically, the void ratio and effective stress are considered uncoupled, and changes in soil volume are rarely considered when implementing soil water retention curves in these equations. This study aims to address these deficiencies by discussing the coupled effect of hydraulic and mechanical processes in unsaturated soils and presenting a semiempirical model to predict the small-strain shear modulus, Gmax, of unsaturated low plasticity soils subjected to volume and effective stress changes along different mechanical and hydraulic stress paths. Predictions from this model and three other recently proposed models in the literature are compared with experimental results obtained from a series of suction-controlled bender element tests on silty soil specimens to validate the proposed model. The comparison reveals that the model proposed in this study provides more consistent predictions of the small-strain shear modulus during hydraulic hysteresis, as well as different paths of loading and unloading.