Stress Zone Research Articles

ANGLED DENTAL IMPLANTS: IMPLICATIONS FOR CLINICAL PRACTICE AND BIOMECHANICAL CONSIDERATIONS

Angled dental implants have emerged as an effective solution in clinical settings where the placement of straight implants is constrained by unfavorable bone positions or the presence of adjacent anatomical structures. The angulation of implants significantly influences stress distribution around the implant, impacting its stability and longevity. Research highlights that the direction of applied loads is critical, as angled implants can generate greater bending and shear forces compared to straight implants, potentially leading to stress concentrations in surrounding bone. Finite element analysis (FEA) is commonly used to model these conditions, offering insights into stress zones and predicting potential failure areas. Bone quality plays a vital role in how implants respond to applied forces, with denser bones effectively dissipating forces while more porous bones are at higher risk of resorption and integration failure. Studies indicate that excessive stresses on angled implants can lead to bone resorption, compromising long-term stability. Therefore, careful consideration of implant angulation, connection type, bone quality, and thorough surgical planning is essential. Recent studies, including those investigating the effects of implant design and bone density on stress distribution, have demonstrated that varying implant threads and angulated abutments affect the stresses experienced by surrounding bone and implants. The findings emphasize the need for appropriate implant selection and a detailed assessment of bone anatomy and patient-specific clinical conditions. By incorporating advanced technologies like FEA, clinicians can enhance their understanding of biomechanical interactions, ultimately leading to improved clinical outcomes and patient satisfaction. Continuous education and the implementation of best practices in dentistry remain vital for the successful application of angled dental implants.

Analytical solution of surrounding rock stress and plastic zone of rectangular roadway under non-uniform stress field

The shape and extent of the plastic zone can effectively reflect the degree of deformation and failure of the surrounding rock. By applying complex variable functions and the theory of elasticity, a mechanical model for the surrounding rock of a rectangular roadway is established. The analytical solution for the stress in the surrounding rock of a rectangular roadway under a non-uniform stress field is derived, and the spatial stress distribution pattern in the surrounding rock of the rectangular roadway is obtained. Furthermore, using the Mohr-Coulomb criterion, the boundary equation of the plastic zone in the surrounding rock of a rectangular roadway is derived, and the morphological characteristics of the plastic zone are obtained. The results indicate that the plastic zones on both sides of the rectangular roadway are arc-shaped. The asymmetry of the stress environment has a significant impact on the plastic zones in the roof and floor of the rectangular roadway, causing the shape of the plastic zones to resemble a “petal” pattern. The lateral pressure coefficient and the height-to-width ratio have a significant impact on the stress distribution and the morphological characteristics of the plastic zone in the surrounding rock of the rectangular roadway. By validating the computational accuracy of the analytical solution through numerical simulations and conducting an engineering applicability analysis based on a coal mine roadway, it has been demonstrated that the analytical calculation method is both rational and possesses good engineering applicability. This provides reliable theoretical guidance for the design calculations and construction planning of similar roadway projects.

Study on the Control Effect of Borehole Gas Extraction in Coal Seams Based on the Stress–Seepage Coupling Field

In order to determine the reasonable parameters of high-gas and extra-thick coal seam drainage, considering the factors of the coal seam metamorphic degree, stress condition, gas occurrence state, and permeability dynamic change, the gas desorption, diffusion, and transport process of coal seam gas are analyzed. A secondary distribution model of coal around the borehole, a porosity variation model of coal around the borehole, a stress–seepage coupling model, a pore flow model of the pressure-driven transition flow zone, and a free molecular flow zone are established. Taking the gas drainage of Zhangcun Coal Mine of Lu’an Group as the research object, the influence of drilling hole diameter, coal seam permeability, gas original pressure, and other factors on the control range of coal seam drainage drilling is simulated by ANSYS Fluent 6.3.26. The results show that secondary stress distribution occurs in the coal seam drill hole under the action of lead stress, which leads to the change in porosity; the seepage zone, transition zone, molecular flow zone, and original rock stress zone are presented around the drill hole; and the range of influence of the drill hole is mainly based on the seepage zone and the transition zone, supplemented by the molecular flow zone. The control range of the drill hole is in a positive proportional relationship to the diameter of the drill hole, the porosity of the coal seam, and the original pressure of the gas.

The Role of Psychological Resilience, Coping Mechanisms and Locus of Control in Managing Students' Perceived Stress during Exams

Abstract: With this study we provide conclusive evidence on the importance of psychological resilience, coping mechanisms, self-esteem and locus of control for optimal adaptation in situations of intense psychological stress, such as the stress perceived by students in exam situations. The data reveal that out of 120 students included in the study group, 29 students, i.e., 33.2 ⁒ were in the high stress zone and 4 students, i.e., 3.3 ⁒ were in the dangerously high stress zone, which can be explained by the poor functioning of some coping mechanisms and psychological resilience. For example, self-blame as a variable of coping mechanisms has a negative influence on the level of perceived stress and explains 49.72% of the stress level. Also, by comparison, some variables play a positive role in stress management and explain in different proportions the level of perceived stress, such as perspective-taking (35.64%), positive reappraisal (27.64%), positive refocusing (20.25%) or self-esteem (12.33%). The study also revealed that females better manage specific manifestations of perceived stress in exam situations, proving that they more easily establish interpersonal relationships, which in turn can support some healthy response behaviors, how to solve specific tasks and adapt more easily to some specific demands of academic work.

Mesoscopic analysis on the coral aggregate reinforced concrete column under axial and eccentric compression

Coral aggregate concrete (CAC) has been identified as a promising building material for reef engineering construction, yet its practical application remains challenging due to incomplete research on the mechanical behaviors of the CAC beam and column components. In this study, a 3D mesoscale modeling approach considering the heterogeneity of CAC was utilized to investigate the mechanical performance of coral aggregate reinforced concrete columns (CARCCs) under axial and eccentric compression. Through numerical delineation of failure processes and damage mechanisms at the mesoscale, comprehensive parametric analysis integrating both numerical simulations and experimental validations were executed to assess the load-bearing capacity of CARCC. Results indicate that the mesoscale model has significant reliability in simulating the deformation and cracking failure behaviors and analyzing the load-displacement relationships of CARCC under axial and eccentric compression loads. When under axial loads, macroscopic cracks in CARCC primarily develop in an oblique manner, precipitating significant concrete spalling and extensive cracking failure along the longitudinal axis. Under eccentric loads, failure advances from crack initiation at load points to abrupt vertical fractures in stressed zones, manifesting a decrement in the load-bearing capacity with escalating eccentricity. Furthermore, the strength grade and reinforcement ratio exert a profound influence on the load-bearing capacity, with disparate impacts under varied loading conditions. It is concluded that reinforcement strategies tailored to specific loading conditions have significant implications for the design and safety of reinforced concrete structures in reef engineering projects.

Failure characteristics of overlying strata and mechanism of strong ground pressure during the large‐scale and continuous mining of deep multi working faces

AbstractIn this study, a three‐dimensional large‐scale numerical model is established to investigate the failure characteristics of overlying strata and mechanism of strong ground pressure induced by excavation disturbance from multiple working faces. The characteristics of overlying strata fractures, heights of the caving zone and the fracture zone, and evolution of the stress field are systematically analyzed. The numerical simulation results reveal that the height of the caving zone after mining is 8.1 m, and that of the fracture zone is 27.3 m under the conditions of gently inclined thin coal seams. These findings are consistent with the theoretical results. The fracture development process can be divided into three stages: extensive development of new fractures, partial compaction of fractures, and closure of numerous fractures. In the structure of the post‐mining overlying rock, four stress zones are identified as follows: two zones of stress concentration at both ends of the working face, respectively, a zone of relatively high stress at the middle of the working face with low overlying strata, and a zone of stress fully released at the middle of the working face with high overlying strata. Comprehensive analysis of the maximum vertical stress of the cross section and the stress of the working face indicates that the stress increases significantly when mining enters the gob square stage and the roof does not collapse timely.

Deformation mechanism and control technology of gob-side entry retaining with roadside backfilling: a numerical analysis and field investigation

The technology of gob-side entry retaining (GER) has the advantages in terms of higher resource recovery rate and lower drivage ratio. In this study, the GER implementation in N1217 panel in Ningtiaota Coal Mine, to verify the adaptability of the gob-side entry retaining with roadside backfilling, the FLAC3D numerical model was established, the stress evolution law and plastic zone distribution of the roadway surrounding rock were analyzed, the deformation characteristics of the roadway during the mining period were revealed, the roadway surrounding rock control technology was proposed, and the development of roof cracks was analyzed. The numerical results show that during the mining of the working face, the roadside backfill body and gangue are jointly loaded, the peak stress of the surrounding rock is transferred from the mining side to the solid coal side, the plastic zone of the roof and the solid coal side increases significantly, and the tensile and shear mixed failure occurs. Based on the evolution characteristics of the stress and plastic zone of the surrounding rock during the mining period of the working face, a collaborative control technology of the surrounding rock based on gangue retaining bracket + roadside backfill + bolt (cable) is proposed, and the borehole peep shows that the roadway is affected by roof fracture rotation and subsidence, which leads to the development of roadway overburden cracks and failures to the depth. The monitoring results indicate that the control measures are highly effective, with minimal roadway convergence observed and stable bolt (cable) supporting forces recorded. Additionally, hydraulic support resistance monitoring confirms that the roadway remains stable. It can ensure the safe mining of the working face of the Ningtiaota coal mine and other similar roadways.

Welfare and performance benefits of shade provision during summer for feedlot cattle in a temperate climatic zone.

There is increasing interest from cattle lot-feeders in the use of shade to mitigate the effects of a potential heat stress event, though it is unclear whether the reported benefits of shade in previous studies conducted in more high-risk heat stress zones are pertinent in cooler temperate zones. The objectives of this study were to measure the welfare and performance benefits of shade provision for lot-fed cattle at a commercial feedlot located in a mild heat-stress risk zone in Western Australia. Six blocks of black Angus (Bos taurus) steers were inducted into the feedlot over six time-windows across a southern hemisphere summer, with 80 cattle per block housed in a partially shaded pen (providing 3.125 m2 of shade per animal) and 80 in an unshaded pen. Parameters assessed in 960 cattle over the first 70 days in the feedlot included weight gain, feed intake, and physiological and behavioral indices of overall health and welfare. Over the months of October through to May in which the experiment was conducted, shaded cattle demonstrated a modest 0.13kg overall increase in average daily gain across the 70-day feedlot period (P = 0.13). There was no difference in dry matter intake between any block or treatment. The physiological and behavioral markers of health and welfare revealed that, even during to hottest times of the experiment, the cattle were quite able to thermoregulate, via increased panting and seeking shade (if available), to maintain physiological homeostasis. In addition, we measured the effect of heat stress and shade provision on the affective state of the cattle. Qualitative behavioral assessment was used to indicate that the cattle in the 'no stress' temperature humidity index (THI) category and the shaded cattle in the 'moderate stress' THI category displayed the most positive demeanor (P < 0.05), being described as more 'settled and sociable', while the unshaded cattle in the 'moderate stress' THI category and all cattle in the 'severe stress' THI category were described as more 'agitated/anxious' (P < 0.05). Overall, the findings from the present study suggest that there are definite welfare and modest performance benefits associated with providing cattle with shade in summer in a feedlot situated in a temperate climatic zone.

Detection of underground natural gas pipeline micro-leakage based on UAV hyperspectral remote sensing and GIS

ABSTRACT Detection of underground natural gas pipeline micro-leakage based on unmanned aerial vehicle (UAV) hyperspectral remote sensing and GIS. Hyperspectral images can indirectly detect underground natural gas pipeline micro-leakage through spectral and spatial variation characteristics of surface vegetation. However, most of existing studies were based on ground-mounted platforms, which could only perform small-range single-point detection and might occur misidentifications. UAV hyperspectral remote sensing can allow wide-range detection of surface vegetation. Moreover, underground pipeline distribution GIS data can provide prior knowledge about leakage points to exclude misidentifications. Therefore, a natural gas pipeline micro-leakage experiment was set up. UAV hyperspectral images of grasslands and pipeline distribution vector data were obtained, which led to a proposed new wide-range multi-points detection methodology of underground natural gas micro-leakage. Firstly, the vegetation identification index (WVI) R 470 + R 674 / R 555 + R 750 was designed based on WOA–VMD (whale optimization algorithm – variational modal decomposition) to segment and extract the vegetation stress zones. Then, UAV- and GIS-based natural gas micro-leakage vegetation stress identification model was constructed to obtain the leak points of natural gas micro-leakage. Finally, the recognition ability was evaluated by comparing with three stress vegetation identification indices proposed in previous studies. The result showed that there was no missing or false detection in identification results; the identification and positioning effect was better than other indices, which could meet the practical application requirements.

Analysis of Spatial and Temporal Trends of Vegetation Cover Evolution and Its Driving Forces from 2000 to 2020—A Case Study of the WuShen Counties in the Maowusu Sandland

The WuShen counties in the hinterland of the Maowusu Sandland are located in the “ecological stress zone” of the forest–steppe desert, with low vegetation cover, a strong ecosystem sensitivity, and poor stability under the influence of human activities. Therefore, it is important to study and analyze the changes in vegetation growth in this region for the purpose of objectively evaluating the effectiveness of desertification control in China’s agricultural and pastoral intertwined zones, and formulating corresponding measures in a timely manner. In this paper, the spatial and temporal variations in the vegetation NDVI in the WuShen counties of the Maowusu Sandland and their response relationships with driving factors were investigated by using a trend test, center of gravity transfer model, partial correlation calculation, and residual analysis, and by using the MOD13A3 vegetation NDVI time series data from 2000 to 2020, as well as the precipitation, temperature, and potential evapotranspiration data from the same period. The results showed the following: ① The regional vegetation NDVI did not fluctuate significantly with latitude and longitude, and the NDVI varied between 0.227 and 0.375 over the 21-year period, with a mean increase of 0.13 for the region as a whole and an increase of 0.61 for the region of greatest change. Of the area, 86.83% experienced a highly significant increase, and the trend in increase around rivers and towns was higher than that in the northwestern inland flow area, with the overall performance of “low in the west and high in the east”. ② Only 2.07% of the vegetation NDVI center of gravity did not shift, and the response with climate factors was mainly characterized by having consistent or opposite center of gravity changes with precipitation and potential evapotranspiration. ③ Human activities have been the dominant factor in the vegetation NDVI change, with 75.89 percent of the area positively impacted by human activities, and human activities in the southwest inhibiting the improvement of vegetation in the area. The impact of human activities on the unchanged land type area is increasing, most obviously in the farmland area, and the impact of human activities on the changed land type area is gradually decreasing in the area where the farmland becomes impervious. The vegetation in the area above 1300 m above sea level is degraded by the environment and human activities. The research results can provide scientific support for the implementation of ecological fine management and the formulation of corresponding ecological restoration and desertification control measures in the Maowusu Sandland. At the same time, it is expected to serve as a baseline for other studies on the evolution of vegetation in agro-pastoral zones.

An enhanced transit accessibility evaluation framework by integrating Public Transport Accessibility Levels (PTAL) and transit gap

Rapid urbanization has presented many challenges, notably spatial imbalances between the transit supply and demand within cities. The inequitable distribution of transit supply, which include the transit infrastructure and services, may lead to formation of areas where transit is under provisioned. This work aims to develop an enhanced framework for measuring spatial disparities in accessing transit systems by combining established concepts of Public Transport Accessibility Levels (PTAL) and transit gap. The proposed framework incorporates PTAL as a supply indicator and transit dependent population as the demand indicator while estimating the transit gap. PTAL takes into account the intricate relationship between transit infrastructure and transit services, an aspect that was overlooked by the previous studies on transit gap. Inclusion of PTAL enhances the transit gap evaluation method by offering a deeper understanding and a holistic perspective on the transit system. We demonstrate the proposed approach with an application in Singapore. Additionally, we propose a new classification system based on PTAL and transit gap to distinguish areas where high transit gap is a result of very high demand rather than poor supply. Results show that 44.82 % of the transit dependent population in Singapore lives in high transit gap area out of which 4.69 % population stays in transit desert zones, where supply is poor, and 40.13 % lives in transit stressed zone, where demand is very high. The study also developed a simple decision framework based on PTAL and transit gap scores to suggest effective policy measures for reducing the spatial disparity in transit system accessibility. The findings from the work can aid policymakers and transport planners in land-use and transport planning of cities.

Dimensional change and springback of spherical shell in cryogenic forming

Cryogenic forming has been developed to manufacture thin-walled curved aluminum alloy components, whose final dimensions are affected by cryogenic shrinkage and springback. Therefore, dimensional changes of spherical shell in cryogenic forming were studied theoretically and experimentally. The cryogenic forming process was discussed to elucidate the factors affecting the dimensional change. The stress distribution was analyzed to qualitatively reveal the springback behavior. Cryogenic dimensional measurement devices were built to quantitatively evaluate the dimensional changes in the forming processes of punch cooling, springback, and specimen restoration to room temperature. The temperature dependencies of the elastic modulus and expansion coefficient were modeled to quantitatively calculate the effect of thermal expansion and contraction on the dimensions of specimen and punch. The theoretical analysis results indicate that depth reduction and opening expansion are produced by cryogenic springback, determined by the radial stress, hoop stress, and bending moment in different deformation regions. The cryogenic springback in the biaxial tensile stress zone was reduced by 37.8 % owing to the increasing radial deformation and decreasing bending deformation. In contrast, cryogenic springback in the tensile-compressive stress zone increased by 30.8 %. The punch cooling shrinkage and specimen warming expansion in depth direction can reduce for the dimensional deviation caused by springback but cause the opposite effect in hoop direction. Expansion and shrinkage were effectively predicted using the proposed model, with an error of less than 16 %. The deformation region of the biaxial tensile stress can be enlarged by the significantly improved hardening ability at cryogenic temperature, which benefits enhancing deformation uniformity and further reduces springback. Therefore, cryogenic forming offers considerable potential for the precision manufacturing of aluminum alloy deep-cavity thin-walled components.

Напряженное состояние слоистого массива, вмещающего горную выработку круглого поперечного сечения

The elastoplastic problem of the stress state of layered rock mass containing an extended single mine working is solved in the following sequence. A stress field is built in the parts of mass adjacent directly to the mine working that form an extremely stressed area (the area of inelastic deformations). Then the area is spread into the rock mass, and the stress field is built in it in accordance with the characteristics method developed by V.V. Sokolovsky to be applied to the calculation of granular and coherent media. The method has been developed to solve problems of differential equations of the equilibrium of continuum mechanics jointly with general and special strength criteria of Coulomb–Mohr. This non-linear system belongs to hyperbolic equations. The characteristics method alternately solves three boundary value problems for a number of specific areas of the extremely stressed rock mass. Then, by substituting the extremely stressed area with stresses at its boundary, the elastoplastic problem is reduced to the boundary value problem of theory of elasticity for a medium with reinforced cutout, whose dimensions comply with dimensions of the extremely stressed area. The problem is solved by using the boundary element method and controlled by compliance with static boundary conditions at the boundary of plastic area and elastic region. The elastoplastic problem of the stress state of a layered array containing an extended single mine working is solved in the following sequence. First, a stress field is constructed in the parts of the array adjacent directly to the mine working, with from an extremely stressed zone (a zone of inelastic deformations). Further, this zone extends deep into the array, and the stress field in it is constructed by the method of characteristics developed by V.V. Sokolovsky in relation to the calculation of bulk medium. The method is designed to solve a system of differential equations of equilibrium of continuum mechanics together with general and special Coulomb — Mohr strength criteria. This nonlinear system belongs to hyperbolic equations. The method of characteristics alternately solves the boundary value problems for a number of characteristic sections of the extremely stressed zone of the array. Then, by replacing the extremely stressed zone with stresses at its boundary, the elastically plastic problem is reduced to the boundary value problem of the theory of elasticity for a medium with a reinforced cutout, the dimensions of which correspond to the dimensions of the extremely stressed zone. It is solved by the boundary element method and is controlled by the fulfillment of static boundary conditions at the boundary of the plastic zone and the elastic region.

Microstructure-Linked Mechanical Properties of P91-Incoloy 800HT Dissimilar Metal Welds

Dissimilar metal welds (DMWs) between P91 steel and Incoloy 800HT® using shielded metal arc welding (SMAW) with ENiCrCoMo-1 filler electrode were characterized in detail. The impact of multiple weld passes on microstructure in the heat-affected zone (HAZ) and weld fusion zone (WFZ) was thoroughly investigated. Postweld heat treatment (PWHT) impacts on mechanical characteristics and microstructure were also observed. The DMW was observed with heavy C, Cr, and Mo microsegregation in the WFZ, which deteriorated mechanical strength. The microstructural changes directly affected the mechanical behavior of the DMW. The ultimate tensile strength of the weld fusion zone was low at 576 MPa compared to the base metals’ strength. The tensile specimens failed in the IN 800HT base metal and WFZ. The WFZ had significant microsegregation near the solidified grain boundaries (SGBs). The metallurgical heterogeneity in the WFZ caused the formation of localized stress zones, which directly affected the mechanical behavior of the WFZ. The carbide particles influenced the microhardness in the WFZ and P91 HAZ regions. The PWHT successfully homogenized the microhardness in the WFZ and P91 HAZ regions. The impact toughness decreased to 64 J from 82 J after PWHT due to precipitation at SGBs and its coarsening. The SMAW process involves multiple thermal cycles during welding. The deposition of filler metal in multiple welding passes created uncontrolled variations in the solidification behavior of the WFZ. Microsegregation had a detrimental impact on the microstructure and mechanical properties of the P91 and IN 800HT dissimilar metal welds.

Mechanism of rockburst induced by the microseismic event in the floor strata of high tectonic stress zones: A case study

With the increase of mining scope, rockburst occurs frequently, but its generation mechanism has not been understood comprehensively. Based on a rockburst in the coal pillar area of high tectonic stress zones (HTSZs), this study analyzed the distribution characteristics of large-energy microseismic (MS) events by using data statistics. The mechanical cause of the MS event that induced the rockburst was revealed by means of seismic moment tensor inversion. On this basis, by using numerical simulation, this study explored the distribution characteristics of static load in rockburst area and the effect of dynamic load in the floor, and then proposed the rockburst mechanism. The results show that under the squeezing action, the floor strata in HTSZs implode and transmit energy outward in the form of stress waves. This causes the cumulative damage and stress of the coal body in the fast track of coal pillar area increase in a short time. Since the coal in this area has already been in the critical stress state, small stress changes may lead to coal failure and rockburst. In this case of rockburst, the high static load of coal is the main force source, and the dynamic load plays a role in increasing coal body damage and inducing rockburst. Combined with seismic moment tensor inversion and numerical simulation, this paper proposes a rockburst research scheme, which makes the simulation of dynamic load more reasonable. The results provide the theoretical basis for rockburst control under similar conditions.

Study of Sleep Quality in Geopathic Stresses Areas and Efficacy of Enviromat in Improving the same- A Quantitative Study

A good night's sleep is essential for maintaining a healthy body and mind, as our body cells repair themselves during sleep. However, various factors can disturb our sleep, and Geopathic Stress is considered one of the contributing reasons. Geopathic Stress refers to the disturbance of natural energy flows, primarily caused by geological features such as underground water veins, mineral deposits, and fault lines, which can lead to disruptions in health. So, we aim to investigate the impact of Geopathic Stress on sleep quality and the efficacy of Enviromat as a potential solution. In this study, a total of 22 subjects were screened and recruited as per the inclusion and exclusion criteria. The research began with a literature review of relevant studies to identify the effects of Geopathic Stress on sleep quality. After reviewing the relevant research studies, a protocol was formed and presented to the Institutional Ethics Committee for approval, at All India Institute of Medical Sciences, New Delhi. Once the protocol was approved, Geopathic Stress zones were identified in the Sleep lab, where subjects slept on the beds in these zones. Subsequently, the Enviromat was evaluated for its efficacy to mitigate the harmful effects of Geopathic Stress on sleep quality. Complete data of 20 subjects was recorded and analysed with and without Enviromat with a gap of 10 days between two readings. The results indicated that sleep quality improved significantly (from 80.78 ± 7.83 to 87.08 ± 5.70; p-value = 0.0021) in most subjects when the Enviromat was used, suggesting its potential effectiveness in counteracting the negative effects of Geopathic Stress on sleep. These findings provide valuable insights into the relationship between Geopathic Stress and sleep and highlight the Enviromat as a promising intervention.

Thermomechanical Analysis of Cement Hydration Effects in Multi-layered Pier Head Concrete: Finite Element Approach

Mass concrete plays a crucial role in infrastructure development, yet its complex thermo-mechanical behavior poses challenges, especially in the construction of multi-layered structures like pier heads. This study investigated the thermo-mechanical behavior of a pier head during its concreting process in three stages, including the influence of temperature differences that impact the thermomechanical balance of the concrete. By utilizing the ABAQUS software, thermo-mechanical analysis was conducted to simulate temperature fluctuations during cement hydration. The model integrates thermal analysis to simulate temperature fluctuations during cement hydration and stress distribution during construction, validated through mesh convergence studies and field data comparison. The mechanical analysis considered concrete properties, temperature variations, and construction phase. Nonlinear material behavior and contact interactions between layers were incorporated to obtain a realistic simulation. The results indicated that a multi-layer system can balance temperatures, reducing thermal stress-induced cracking risks. Furthermore, specific test points within the pier head were assessed, revealing potential internal cracks by comparing thermal stresses to the concrete’s tensile strength. This research offers insight into pier head conditions during construction, highlighting critical stress zones, crack prediction, and construction sequence efficacy.

Seismotectonic Setting of the Andes along the Nazca Ridge Subduction Transect: New Insights from Thermal and Finite Element Modelling

The structural evolution of Andean-type orogens is strongly influenced by the geometry of the subducting slab. This study focuses on the flat-slab subduction of the Nazca Ridge and its effects on the South American Plate. The process of flat slab subduction impacts the stress distribution within the overriding plate and increases plate coupling and seismic energy release. Using the finite element method (FEM), we analyse interseismic and coseismic deformation along a 1000 km transect parallel to the ridge. We examine stress distribution, uplift patterns, and the impact of megathrust activity on deformation. To better define the crust’s properties for the model, we developed a new thermal model of the Nazca Ridge subduction zone, reconstructing the thermal structure of the overriding plate. The results show concentrated stress at the upper part of the locked plate interface, extending into the Coastal and Western Cordilleras, with deeper stress zones correlating with seismicity. Uplift patterns align with long-term rates of 0.7–1 mm/yr. Cooling from flat-slab subduction strengthens the overriding plate, allowing far-field stress transmission and deformation. These findings provide insights into the tectonic processes driving stress accumulation, seismicity, and uplift along the Peruvian margin.

Resistance characteristics of Y-shaped sleepers for ballasted track under slope influence

The stability of ballasted track is significantly influenced by ballast bed resistance, which inevitably decreases on steeply graded track. Y-shaped sleepers generate considerable ballast bed resistance, but current studies exhibit a research gap in analyzing the performance of resistance variations for Y-shaped sleepers on steep railway slopes. In order to study the mechanical characteristics of the ballasted track with Y-shaped steel sleepers, a discrete element model of the ballast bed for a large-slope railway is established, and its accuracy is validated. The changes of longitudinal and lateral resistance of the ballast bed and the characteristics of the ballast bed resistance of the Y-shaped steel sleeper applied to different slope lines are analyzed. The results show that both the longitudinal and lateral resistances of the ballast bed can be modeled as linearly decreasing with increasing slope, with minimum values of 14.59 kN (longitudinal), 14.33 kN (lateral, tail to head), and 12.09 kN (lateral, head to tail), respectively. The longitudinal resistance provided by the sleeper sides, bottom, and end is minimally affected by the slope. The resistance contributed by the front Y limb increases progressively (from 66 % to 72 %), while the resistance from the rear Y limb decreases (from 11 % to 5 %). The ballast bed support stiffness exhibits a maximum reduction of 18.21 %. Affected by the slope, the longitudinal resistance of the Y-shaped steel sleeper is reduced more than the lateral resistance. The amplitude and influence zone of the longitudinal stress experienced by the ballast are increased with the slope. The study indicates that despite the reduction in resistance characteristics of the Y-shaped sleeper-ballast system due to slope influence, it still maintains high performance.

Impact assessment of precipitation and temperature trends on crop yield in water stress zone of Bundelkhand, India

Impact assessment of precipitation and temperature trends on crop yield in water stress zone of Bundelkhand, India