This research explores the stabilization of clay soil through the application of geopolymer binder derived from silicomanganese slag (SiMnS) and activated by sodium hydroxide (NaOH). This research aims to evaluate the effects of key parameters, including the percentage of slag, the activator-to-stabilizer ratio, and curing conditions (time and temperature), on the mechanical properties of the stabilized soil. Unconfined compressive strength (UCS) tests were conducted to assess improvements in soil strength, while scanning electron microscopy (SEM) was employed to analyze the microstructural changes and stabilization mechanisms. The results demonstrated that clay soil stabilized with SiMnS-based geopolymers exhibited significant strength enhancement. Specifically, the sample stabilized with 20% SiMnS and an activator-to-slag ratio of 1.6, cured at room temperature for 90 days, achieved a UCS of 27.03 kg & frasl;cm2. The uniaxial strength was found to be positively correlated with the SiMnS content, activator ratio, curing time, and temperature. Additionally, the strain at failure remained below 1.5% for all samples, indicating a marked improvement in soil stiffness. SEM analysis revealed that geopolymerization led to the formation of a dense matrix, enhancing soil particle bonding and overall durability. These results emphasize the potential of SiMnS-based geopolymers as a sustainable and effective soil stabilizer for geotechnical applications.

The generation of excess pore water pressure (EPWP) and liquefaction characteristic of soils under seismic loading have long been topics of interest and ongoing discussion. Based on the structural state exhibited in the liquefaction process, the mechanical property of saturated coral sand is divided into solid, pseudo-fluid, and liquid phases. New indices, zeta q (generalized deviator strain evolution) and zeta(y)q (generalized deviator strain evolution rate), are proposed to evaluate the evolution and evolution rate of complex deformation. In the solid phase, the saturated coral sand primarily exhibits the properties of a continuous solid medium, the peak EPWP ratio (rup) shows a power correlation with generalized deviator strain evolution amplitude (zeta qa). While in the pseudo-fluid phase, the saturated coral sand primarily exhibits mechanical behavior characteristic similar to that of a fluid, and the rup shows a significant arctangent function relationship with generalized deviator strain evolution rate amplitude (zeta(y)qa). The correlation of rup with zeta qa and zeta' qaduring liquefaction is significantly affected by loading conditions (cyclic stress ratio, CSR, loading direction angle, alpha sigma, and loading frequency, f). To quantify the impact of these loading conditions on the generation of rup in different phases, unified indicators delta S (for the solid phase) and delta L (for the pseudo-fluid phase) are defined. Eventually, An EPWP model based on mechanical property exhibited in different phases is developed, which has normalized the effects of loading conditions. It provides a comprehensive framework to predict the rup of saturated coral sand under complex geological activities, and this model facilitates the understanding and simulation of the mechanical properties and behavior of saturated coral sand during the liquefaction process.

Determining the optimal damping value of the isolation system in tall structures is challenging as it requires parametric studies and time-consuming nonlinear time-history analyses. Consequently, the influence of different parameters, such as displacement limitation, on the optimal damping of isolators in tall structures remains unclear. This study aims to investigate the optimal damping of isolators in tall structures under two scenarios: a) changing the displacement capacity of the isolators in proportion to the increase of damping (variable gap); b) maintaining a constant displacement capacity of the isolators as the damping increases (constant gap). The study also explores the influence of two additional parameters on the optimal damping of the isolation system, namely the ratio of isolator to superstructure period (TM/TS) and the soil type. The optimal design procedure is illustrated with reference to a case-study 14-story isolated steel structure with an ordinary concentrically braced frames (OCBF) system, isolated with the triple friction pendulum isolator (TFPI) system. The modified endurance time (MET) method is utilized to analyze the seismic response of the case-study structure under increasing levels of earthquake hazard. The analysis reveals that increasing damping in both constant and variable gap modes can effectively reduce the damage level of the structure. However, the effectiveness of increasing damping is limited and influenced by factors such as soil softness and the TM/TS ratio. The optimal damping values are determined based on the desired performance levels for both structural and nonstructural acceleration-sensitive components.

The deformation behaviors of soft clay under cyclic loading were investigated with constant loading frequency; however, the response frequency of the subgrade soil varied when the train passed by. Moreover, both deviator stress and confining pressure varied cyclically. Hence, two types of cyclic triaxial tests were conducted on saturated soft clay, in which the differences in deformation behaviors between constant and composite loading frequencies were analyzed, and the impacts of cyclic confining pressure and drained conditions were considered. The strain increment continuously decreased with the progress of the test under cyclic loading with constant loading frequency, while that first decreased, achieving the minimum value at the third loading stage, and then increased under cyclic loading with composite loading frequencies. Nevertheless, compared with the test results of cyclic triaxial tests with composite loading frequencies, the strain with constant loading frequency increased by 65.4% and 117.9% under undrained and partially drained conditions, respectively. The cyclic triaxial tests with constant loading frequency overestimated the strains under cyclic loading. The strain increments were greater in the first loading stage under undrained and partially drained conditions; however, the differences in strain increments between undrained and partially drained conditions in other loading stages can be ignored. Moreover, the effect of cyclic confining pressures was clarified under cyclic loading with composite loading frequencies: the strain ratio of cyclic confining pressures to constant confining pressures decreased from 0.870 to 0.723 as eta increased from 1.00 to 2.00 under undrained conditions, while it increased from 1.227 to 1.837 under partially drained conditions. Nevertheless, the ratios increased linearly with increasing eta under partially drained conditions, and decreased linearly under undrained conditions.

The cutter head, a pivotal component of the tunnel boring machine (TBM), endures high-risk working conditions involving high temperature, pressure, and hardness. The intricacy and variability of working conditions give rise to high torque, substantial thrust, and stochastic impact loads, ultimately leading to the damage and failure of the cutter head. In this paper, the mechanical and fatigue properties of the 8 -meter-class spoke-web composite cutter head have been investigated through the finite element method (FEM) more academically. Specifically, this article explores the typical working conditions (full load, eccentric load, and extreme condition) and different geologies (soft soil, composite formation, and hard rock) that the cutter head encounters. The findings demonstrate that under extreme working conditions, the cutter head experiences a maximum equivalent stress of 250.76 MPa. Additionally, the maximum displacement of 4.83 mm occurs on the outer ring when subjected to a one-half eccentric load. Concisely, the FEA validates the cutter head's structural rationality in stiffness and strength. Furthermore, a fatigue durability analysis of the cutter head structure was conducted using nCode DesignLife based on the stress method, determining its fatigue life range to be between 6.857E+4 and 1.253E+7 cycles, with an error not exceeding 20% compared to the theoretical fatigue life. This research provides valuable insights for the structural design and fatigue life studies of cutter heads for TBMs.

Southwest China was affected by two extreme droughts in the autumn to spring of 2012-2013 and the winter to summer of 2020-2021. These droughts caused water depletion, crop damage, and socio-economic disruption. However, little is known about the accurate representation of the two drought events and the responses of vegetation to the droughts. We used multiple vegetation indices and multi-source climate data to quantify the spatiotemporal variations of the two events. We assessed the different responses of vegetation greenness in Southwest China to the two drought events to determine the underlying mechanisms. Vegetation greenness in Southwest China showed different responses to the two events due to differences in the early hydrothermal conditions. The 2012-2013 autumn-spring drought suppressed vegetation growth in Southwest China, with a total decrease of 0.17 (31.7 %) in the normalized difference vegetation index relative to the baseline conditions in the early stage of the drought. The decrease in precipitation and soil water depletion in late summer 2012 aggravated the decrease in vegetation greenness from winter 2012 to spring 2013. By contrast, during the winter-summer drought in 2020-2021, there was an increase of 0.22 (52.3 %) in the normalized difference vegetation index in January-March 2021 relative to the baseline conditions. Adequate precipitation and soil water in the late summer to autumn of 2020 compensated for water loss due to the extreme drought, and, concurrently, more downward solar radiation and warmer conditions linked to less cloudiness contributed to vegetation greening in spring 2021. These results show that early hydrothermal conditions have a vital role in the different responses of vegetation greenness to extreme drought events. These results will help in water management and ecosystem protection in the current background of more frequent extreme weather and climate events resulting from the global climate crisis.

To investigate the impact of rainfall on the stability of granite residual soil slopes, indoor model box tests were conducted at three rainfall intensities (30, 60, 90 mm/h) and two rainfall durations (3. 12 h). The variations in wetting front and vertical displacement were monitored. PFC discrete element software was used to simulate direct shear tests of granite residual soil, calibrate the mesoscopic parameters of granite residual soil for varying moisture contents, and develop a discrete element slope model. The analysis concentrated on the displacement and rotation fields, instability indicators, force chains, and fabric anisotropy to reveal the mesoscopic deformation and mechanical mechanisms underlying slope instability in the model box tests. The results show that when the rainfall intensity reaches 60 mm/h or above, the slip and disturbance range of the slope expand significantly, and the slip body exhibits a circular are shape along the slope face. The slip loss rate of the slope initially decreases and then increases with prolonged rainfall; short-term low-intensity rainfall can stabilize the slope, but continuous rainfall significantly increases the slip loss rate. After 9 hours of rainfall, the displacement and rotation angle of soil particles in the slope increase markedly, forming a distinct circular are slip failure surface. Furthermore, after 9 hours of rainfall, the distributions of force chains and contact force anisotropy within the slope change significantly, with force chains on the slip surface breaking and densely concentrating in stable regions.

The widespread distribution of saline soil in the severe cold regions of northwest China has caused dual damage to concrete structures, including freeze-thaw cycles and sulfate erosion, seriously threatening the adhesive performance of interface agents. To solve the problem, the evolution law of the interface adhesive performance of the interface agent in standard curing, natural exposure, freeze-thaw cycle and sulfate attack environment was studied by modified acrylate lotion. The results indicated that environmental factors have a significant impact on interface strength, with the destructive effect of freeze-thaw cycles being the most prominent. The modified acrylate lotion improved the interface performance through a triple action mechanism: (1) penetrated the matrix to form a pore bolt structure, enhancing the mechanical anchoring effect; (2) The complexation of carboxylic acid carbonyl groups with Ca2+ enhanced the chemical adhesive strength; (3) Its flexibility and filling effect reduced freezing pressure, refined pores, and effectively inhibited water migration and ion erosion. The study further revealed the key mechanisms of interface pore coarsening, and pore plug structure degradation in freezethaw environments, providing new solutions and theoretical support for concrete repair in cold regions.

Engineered loess-filled gullies, which are widely distributed across China's Loess Plateau, face significant stability challenges under extreme rainfall conditions. To elucidate the regulatory mechanisms of antecedent rainfall on the erosion and failure processes of such gullies, this study conducted large-scale flume experiments to reveal their phased erosion mechanisms and hydromechanical responses under different antecedent rainfall durations (10, 20, and 30 min). The results indicate that the erosion process features three prominent phases: initial splash erosion, structural reorganization during the intermission period, and runoff-induced gully erosion. Our critical advancement is the identification of antecedent rainfall duration as the primary pre-regulation factor: short-duration (10-20 min) rainfall predominantly induces surface crack networks during the intermission, whereas long-duration (30 min) rainfall directly triggers substantial holistic collapse. These differentiated structural weakening pathways are governed by the duration of antecedent rainfall and fundamentally control the initiation thresholds, progression rates, and channel morphology of subsequent runoff erosion. The long-duration group demonstrated accelerated erosion rates and greater erosion amounts. Concurrent monitoring demonstrated that transient pulse-like increases in pore-water pressure were strongly coupled with localized instability and gully wall failures, verifying the hydromechanical coupling mechanism during the failure process. These results quantitatively demonstrate the critical modulatory role of antecedent rainfall duration in determining erosion patterns in engineered disturbed loess, transcending the prior understanding that emphasized only the contributions of rainfall intensity or runoff. They offer a direct mechanistic basis for explaining the spatiotemporal heterogeneity of erosion and failure observed in field investigations of the engineered fills. The results directly contribute to risk assessments for land reclamation projects on the Loess Plateau, underscoring the importance of incorporating antecedent rainfall history into stability analyses and drainage designs. This study provides essential scientific evidence for advancing the precision of disaster prediction models and enhancing the efficacy of mitigation strategies.

The impact of the field conditions on needle-punched mulches made of cellulose fibres and PLA biopolymer during the 300 days of exposure was investigated. The study observed the degradation of nonwoven mulches during specific exposure periods (30, 90, 180 and 300 days), evaluating their mechanical, morphological and chemical properties. The impact of nonwoven mulches on soil temperature and moisture, consequently on the number of microorganisms developed beneath mulches after 300 days of exposure, were analysed and associated with obtained results complementing comprehension of nonwoven mulch degradation. The findings show that nonwoven mulches made from jute, hemp, viscose and PLA fibres change when exposed to environmental conditions (soil, sunlight, rainfall, snow, ice accumulation, air and soil temperatures, wind). The changes include alterations in colour, structure shifts and modifications in properties. The results highlight the degradation pathways of cellulose and PLA mulches, revealing that cellulose-based fibres degrade through the removal of amorphous components, leading to increased crystallinity and eventual structural breakdown. WAXD findings demonstrated that microbial and environmental factors initially enhance crystalline regions in cellulose fibres but ultimately reduce tensile strength and flexibility due to amorphous phase loss. FTIR analysis confirmed the molecular changes in cellulose chains, particularly in pectin and lignin, while SEM provided direct evidence of surface damage and fibre disintegration. Furthermore, it was found that fibre types of nonwoven mulch influence soil moisture retention and soil microbial activity due to a complex interplay of fibre composition, environmental conditions and nonwoven fabric characteristics. Comprehensive mechanical, morphological and chemical results of different types of nonwoven mulch during the 300 days of exposure to the field conditions provide valuable insights into sustainable practices for using nonwoven mulches for growing crops.