In highway construction across the southeastern coastal regions of China, granite residual soil is widely used as subgrade fill material in pavement engineering. Its mechanical behaviour under dynamic loads warrants in-depth investigation. Dynamic events such as vehicular traffic and earthquakes are complex, involving multidirectional loads. The dynamic behaviour of soil under bidirectional cyclic loading differs significantly from that under cyclic loading in one direction. A large-scale bidirectional cyclic direct shear apparatus was utilised to carry on a series of horizontal cyclic direct shear tests on granite residual soil with water contents of 14% and 24% at different normal stress amplitudes (sigma a) (0, 100, 200 kPa). Based on these tests, discrete element method (DEM) models were developed to simulate the laboratory tests. The test results revealed that cyclic normal stress increases dynamic shear strength during forward shear but reduces it during reverse shear. The energy dissipation capacity increases with rising sigma a. The dynamic behaviour of granite residual soil is more significantly affected by cyclic normal stress when the water content is higher. The DEM simulation results indicated that as cyclic shearing progresses, the location of the maximum principal stress (sigma 1) shifts from the top of the specimen toward the shear interface. The distribution of the angle between sigma 1 and the x-axis, as well as sigma 1 and the z-axis, transitions from 'M' distribution to 'Arch' distribution. With increasing sigma a, during forward shear, the magnitude of the maximum principal stress increases, and the orientation of sigma 1 rotates toward the normal direction. Conversely, during reverse shear, the magnitude of the maximum principal stress decreases, and its orientation shifts toward the horizontal shear direction. The material fabric anisotropy coefficient decreases with increasing sigma a, while the anisotropy orientation increases with increasing normal stress.

Volume changes in soil caused by freeze-thaw cycles can affect the shear performance of the saline soil-geotextile interface. To investigate this issue, the study examined changes in shear strength, deformation characteristics, and failure modes of the saline soil-geotextile interface under different numbers of freeze-thaw cycles. The experimental results indicate that with the increase in freeze-thaw cycles, the shear stiffness of the interface initially increases and then decreases, demonstrating the reduction in elasticity and resistance to deformation caused by freeze-thaw cycles. And the enhancement of normal stress can effectively increase the density of the soil and the adhesion at the interface, thereby improving shear stiffness. Meanwhile, the salt content in the soil also significantly impacts the mechanical properties, with notable changes in the dynamic characteristics of the interface as the salt content varies. Furthermore, after freeze-thaw actions, the soil becomes loose, reduces in integrity, features uneven surfaces, and sees increased internal porosity leading to slip surfaces. Trend analysis from this study provides new insights into the failure mechanisms at the saline soil-geotextile interface.

In comparison with normally consolidated soft ground, consolidating soft ground often displays inferior engineering properties, which have not been thoroughly investigated yet. This study aims to investigate the undrained shear characteristics of consolidating soft soil under both compression and extension test conditions. A series of undrained triaxial compression and extension tests are conducted on reconstituted kaolin clay under different degrees of consolidation. The results indicate that the undrained stress-strain curves, the evolution of excess pore water pressure, and the undrained stress paths for both normally consolidated and consolidating soft soils exhibit a similar pattern. It is also found that consolidating soft soil also follows the Mohr-Coulomb failure criterion, which can be expressed in terms of effective consolidation pressure and is considered to be independent of degree of consolidation. The primary difference between normally consolidated and consolidating soft soils lies in the initial tangent modulus, which decreases as the degree of consolidation decreases. Subsequently, a modified Duncan-Chang constitutive model is developed to accurately approximate the measured stress-strain curves of consolidating soft soil. Finally, the proposed model is validated by the experimental data, demonstrating its capability to effectively capture the influence of the consolidating state on shear characteristics.

The physical and mechanical properties of granular soils are strongly related to the overlying stresses to which they are subjected. In particular, during the engineering construction phase, which involves activities like foundation stacking and building construction, the applied loads on the soil increase continuously over time. Unfortunately, current stress-controlled compression geotechnical tests have not adequately considered this situation. Therefore, this study aims to examine the effects of various factors, including void ratio, confining stress, stress loading rate, and particle shape, on both macroscopic shear properties and microscopic characteristics of granular soils under conditions of increasing axial stress in biaxial compression numerical simulations. The results show that: (1) In stress-controlled tests on granular soils, samples exhibit three different shear behaviors as the void ratio varies; (2) the confining stress and particle shape will change the magnitude of the deviatoric stresses and axial strains in the peak state of the sample, but not their trends; (3) the stress loading rate does not affect the strength of the samples. Therefore, the loading rate can be increased appropriately to improve the computational efficiency of the numerical model. These findings will enhance understanding of the time-dependent behavior of granular soils and provide valuable insights for engineering applications, particularly in soil mechanics, foundation treatment, and slope stability.

Wind energy offers significant advantages over fossil fuels, including extensive energy storage and environmental sustainability. Offshore wind turbines serve as the primary technology for harnessing offshore wind power. However, the corrosive effects of the marine environment pose serious threats to their safety and stability. This paper provides a comprehensive overview of corrosion issues affecting steel pipe pile infrastructure, focusing on the following key aspects: (1) Differentiating corrosion mechanisms under various environmental conditions, (2) analyzing the comprehensive corrosion response, particularly the changes in mechanical properties of the pile-soil interface and the bearing capacity of steel pile foundations, (3) summarizing the patterns and trends in corrosion processes to offer theoretical insights for engineering design, and (4) reviewing commonly employed corrosion prevention methods and their respective applicability in relation to specific corrosion mechanisms and responses.

Particle size distribution (PSD) of coral sand is a critical factor that influences the mechanical properties at the coral sand-geogrid (CS-GG) interface, which is affected by both particle breakage and various temperatures. However, relevant researches are scarce currently. This study conducts a series of large-scale interface shear tests on coral sand with three PSD ranges (0.25 similar to 1mm, 1 similar to 2mm, and 2 similar to 4mm) at varying temperatures (5 degrees C similar to 80 degrees C). Experimental results demonstrate that the IB value at the CS-GG interface ascends and then descends with the increase of PSD from 20 degrees C to 40 degrees C. The IB value at the interface descends and then ascends with the increase of PSD from 60 degrees C to 80 degrees C; The PSD curves at the interface indicate that the particle breakage degree of coral sand increases with rising temperature (5 degrees C similar to 40 degrees C); The larger PSD of coral sand, the smaller fractal dimensions (D) of the interface; A mathematical formulation of the relationship between the relative breakage rate (Br) and the D value at interfaces is presented, which considers temperature effects; The relationship between the total input energy (E) and the Br value has been expressed by empirical formulations with different PSD ranges, where the fitting curve for 2 similar to 4 mm coral sand exhibits a hyperbolic pattern.

The shear strength and resistance of granular materials are critical indicators in geotechnical engineering and infrastructure construction. Both sliding and rotation influence the energy evolution of soil granular motion during shear. To examine the effects of particle rotation on shear damage and energy evolution in granular systems, we first describe the transformation of irregularly shaped particles into regular shapes via geometrical parameters, ensuring the invariance of energy density and density. We then analyze the impact of particle rotation on shear-stress variation and energy dissipation through a shear energy evolution equation. Additionally, we establish the relationship between the shear-stress ratio and normal stress, considering particle rotation. Finally, we verify the influence of particle rotation on energy evolution and shear damage through shear tests on irregular calcareous sand and regular silica-bead particles. The results indicate that granular materials do not fully comply with the Coulomb strength criterion. In the initial shear stage, most of the external work is converted into granular rotational-shear energy, whereas in the later stage, it primarily shifts to granular sliding-shear energy. Notably, the sensitivity of the granular rotational energy to a vertical load is significantly greater than that of the granular sliding energy.

Spherical glass beads weaken the influences of particle morphology, surface properties, and microscopic fabric on shear strength, which is significant for revealing the relationship between macroscopic particle friction mechanisms and the particle size distribution of sand. This paper explores the shear mechanical properties of glass beads with different particle size ratios under different confining pressures. It obtains the particle size ratio and fractal dimension D through an optimal mechanical response. Simultaneously, we explore the range of the fractal dimension D under well-graded conditions. The test results show that the strain-softening degree of R-s is more obvious under a highly effective confining pressure, and the strain-softening degree of R-s can reach 0.669 when the average particle size (d) over bar is 0.5 mm. The changes in the normalized modulus ratio E-u/E-u50 indicate that the particle ratio and arrangement are the fundamental reasons for the different macroscopic shear behaviors of particles. The range of the peak effective internal friction angle phi is 23 degrees similar to 35 degrees, and it first increases and then decreases with the increase in the effective confining pressure. As the average particle size increases, the peak stress ratio M-FL and the peak effective internal friction angle phi first increase and then decrease, and both can be expressed using the Gaussian function. The range of the fractal dimension D for well-graded particles is 1.873 to 2.612, and the corresponding average particle size (d) over bar ranges from 0.433 to 0.598. Under the optimal mechanical properties of glass beads, the particle size ratio of 0.25 mm to 0.75 mm is 23:27, and the fractal dimension D is 2.368. The study results provide a reference for exploring friction mechanics mechanisms and the optimal particle size distributions of isotropic sand.

The traction force of the tracked miner is primarily determined by the shear characteristics of deep-sea sediments. The influence of different parameters on the shear characteristics of deep-sea sediments and the particles change law of the soil-track interface are discussed. By constructing the relationship between the particles horizontal displacement and residual shear strength, a novel shear rheological damage model of deep-sea sediments considering the influence of grounding pressure is proposed, and the microscopic mechanism of shear displacement of deep-sea sediments is explained. The results show that the peak shear strength and residual shear strength increase significantly with the increase of grounding pressure, track length, grouser height and shear speed. Moreover, the particles within the soil-track interface move along the lower right of the vehicle operating direction during the shearing process under different working conditions, the change of particle spacing shows a non-linear trend, and a quantitative equation for the horizontal deformation of soil-track interface under the experimental conditions is constructed. Additionally, the new shear model has a high level of accuracy in fitting with the experimental data, the internal particle migration changes on the soil-track interface can be divided into four characteristics: compaction, failure, deformation and translation.

A water conveyance open channel project in the northern Xinjiang region crosses a large area of collapsible loess. The mechanical properties of the collapsible loess have undergone severe degradation after years of exposure to rainfall, evaporation, and seasonal temperature fluctuations, making it highly susceptible to engineering phenomena such as channel foundation collapse and slope failure. To delve into the deterioration mechanism, direct shear, compression, and microscopic scanning tests were conducted on the collapsible loess under dry-wet & freeze-thaw cycles. The deterioration patterns of shear strength and compression properties, as well as their damage mechanisms, were analyzed at both macro and microscopic scales. The results of the study indicate (1) Straight shear test: with increasing the number of dry-wet-freeze-thaw cycles, the peak shear strength exhibits a three-stage trend: rapid decrease, decelerated rate of decrease, and eventual stabilization. The cohesion decreased exponentially, with the largest reduction occurring during the first cycle, and stabilizing after 5 cycles, reaching a degradation degree of 44.55%. The change in internal friction angle, which varied within 2.1 degrees, was less affected by the wet-dry-freeze-thaw cycles, with a maximum degradation of 7.04%. (2) Compression test: the compression curve can be divided into two stages of elastic deformation and elastic-plastic deformation according to the consolidation yield stress sigma(k), and sigma(k) shifts forward as the cycle times increase. The compression coefficient and compression index decreased exponentially or in a power function form with increasing cycle times, indicating reduced overall compressibility of the soil body. (3) Microstructure: through scanning electron microscope (SEM) analysis, under cycling, the number of large pores decreased while the number of medium and small pores increased, with the arrangement tending towards disorder. Large particles gradually transformed into medium and small particles, and their morphology tended to become rounded. Correlation analysis indicates that pore size and its angle are the main factors influencing shear strength. Pearson's correlation coefficient reveals that particle morphology and pore size have the greatest influence on compression indices.