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The large particle sizes of railway ballast and rock fill have meant that conventional techniques used to measure the small-strain stiffness of finer geomaterials have not been adopted, with the consequence that their stiffnesses are poorly defined. In a series of tests on a UK railway ballast, simple adaptations were made to existing local strain measuring systems to account for the larger particle sizes. The study showed that the small-strain stiffnesses are different in second loading compared to virgin loading, but multiple cycles had little further effect on the stiffness. The large particle size was found rarely to have any detrimental effect on the quality of the strain measurements and the two independent measurements of axial strain taken at diametrically opposite locations were generally as consistent as for finer grained soils. As for other soils, the 'external' measurements of strain across the apparatus platens were of little use in determining stiffness. The presence of water did not have a significant effect on the behaviour, and this was confirmed by inter-particle loading tests on single particle contacts. Despite the use of lubricated end platens, there was a significant barrelling of the sample at large shear strains so that the internal measurement of the volumetric change diverged from the external measurement at large strains. The very small volumetric strains that occurred during isotropic loading meant that each sample could only be used to obtain one measurement of the virgin loading stiffness. [ABSTRACT FROM AUTHOR]

High-speed trains running on ballasted tracks intensify the vibration of ballast layers to a greater extent than conventional passenger trains, with detrimental effects to train operations. The stabilisation effect of the geogrid in real railways under high-speed train moving loads remains unclear. Herein, full-scale model tests on a ballasted trackbed with and without geogrid were conducted, and a novel sequential loading system was adopted to apply the train moving loads. The highest train speeds were 300 km/h for the ballasted track without geogrid, and 360 km/h for the ballasted track with geogrid. To monitor the geogrid tension strain, distributed fibre Bragg grating sensors were mounted on the geogrid ribs. It was found that the maximum geogrid tension strain between neighbouring sleepers was six times larger than that beneath the sleepers. The geogrid influence zone in the ballast layer was identified as being at least 15 cm above the geogrid. The dynamic stress on the subballast surface was decreased by about 49% in the stabilised trackbed. The testing results also showed that geogrid stabilisation could reduce ballast breakage from 14·9% to 2·5% and reduce the permanent settlement of ballast layer by 40%. The experimental results presented in the paper provide a benchmark for geogrid-stabilisation modelling and will be referenced for the optimal design of ballasted tracks. [ABSTRACT FROM AUTHOR]

Seismic designs and numerical analyses required fundamental parameters such as damping ratio and shear modulus. In this study, large-scale triaxial cyclic tests were used to investigate the dynamic properties of limestone ballast and electric arc furnace (EAF) slag ballast. The term 'shear stiffness' is typically reported in a normalized form using shear modulus. As the laboratory test results showed, an increase in confining pressure, loading frequency and anisotropy raises the shear modulus of materials. Shear modulus and damping ratio values do not appear to be significantly affected by an increase in loading cycles. Loading frequency plays the most significant role in changing damping ratio values. An adaptive neuro-fuzzy inference system (ANFIS) was also used to predict the normalized shear modulus and the damping ratio in this study. The results of the developed model were consistent with those of the laboratory tests. Moreover, the relations among the dynamic properties were estimatedly determined using the nonlinear regression method. [ABSTRACT FROM AUTHOR]

A fast and accurate method is described for determining the surface movement of railway ballast during a full-scale lateral resistance test. The proposed method utilises commodity camera equipment and open-source Digital Image Correlation (DIC) algorithms, to track individual ballast particles. It does not require time intensive ballast preparation. Tests have been performed under ambient and floodlit conditions, using colour and greyscale processing routes. The results are compared against direct measurements from lateral resistance tests to assess the accuracy of the proposed method, with a range of absolute maximum error between 0.9% and 3.4% under different laboratory conditions. The study shows that this technique is a viable way to track and measure ballast and sleeper movement over wide areas in near real time, which will lead to an increased understanding of the way ballast interactions influence track behaviour. [ABSTRACT FROM AUTHOR]

Purpose – The main objective of the present research is to investigate the benefits of using geogrid reinforcement in minimizing the rate of deterioration of ballasted rail track geometry resting on soft clay and to explore the effect of load amplitude, load frequency, presence of geogrid layer in ballast layer and ballast layer thickness on the behavior of track system. These variables are studied both experimentally and numerically. This paper examines the effect of geogrid reinforced ballast laying on a layer of clayey soil as a subgrade layer, where a half full scale railway tests are conducted as well as a theoretical analysis is performed. Design/methodology/approach – The experimental tests work consists of laboratory model tests to investigate the reduction in the compressibility and stress distribution induced in soft clay under a ballast railway reinforced by geogrid reinforcement subjected to dynamic load. Experimental model based on an approximate half scale for general rail track engineering practice is adopted in this study which is used in Iraqi railways. The investigated parameters are load amplitude, load frequency and presence of geogrid reinforcement layer. A half full-scale railway was constructed for carrying out the tests, which consists of two rails 800 mm in length with three wooden sleepers (900 mm × 90 mm × 90 mm). The ballast was overlying 500 mm thick clay layer. The tests were carried out with and without geogrid reinforcement, the tests were carried out in a well tied steel box of 1.5 m length × 1 m width × 1 m height. A series of laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, was measured in reinforced and unreinforced ballast cases. In addition to the laboratory tests, the application of numerical analysis was made by using the finite element program PLAXIS 3D 2013. Findings – It was concluded that the settlement increased with increasing the simulated train load amplitude, there is a sharp increase in settlement up to the cycle 500 and after that, there is a gradual increase to level out between, 2,500 and 4,500 cycles depending on the load frequency. There is a little increase in the induced settlement when the load amplitude increased from 0.5 to 1 ton, but it is higher when the load amplitude increased to 2 ton, the increase in settlement depends on the geogrid existence and the other studied parameters. Both experimental and numerical results showed the same behavior. The effect of load frequency on the settlement ratio is almost constant after 500 cycles. In general, for reinforced cases, the effect of load frequency on the settlement ratio is very small ranging between 0.5 and 2% compared with the unreinforced case. Originality/value – Increasing the ballast layer thickness from 20 cm to 30 cm leads to decrease the settlement by about 50%. This ascertains the efficiency of ballast in spreading the waves induced by the track.

Understanding the magnitude of biosecurity risks in aquatic environments is increasingly complex and urgent because increasing volumes of international shipping, rising demand for aquaculture products, and growth in the global aquarium trade, are accelerating invasive alien species spread worldwide. These threats are especially pressing amid climate and biodiversity crises. However, global and national biosecurity systems are poorly prepared to respond because of fragmented research and policy environments, that often fail to account for risks across sectors or across stakeholder needs and fail to recognize similarities in the processes underpinning biological invasions. In the present article, we illustrate the complex network of links between biosecurity threats across human, animal, plant, and environment sectors and propose a universal approach to risk assessment. One Biosecurity is a holistic, interdisciplinary approach that minimizes biosecurity risks across human, animal, plant, algal, and ecosystem health and is critical to reduce redundancy and increase cross-sectoral cohesion to improve policy, management, and research in aquatic biosecurity. [ABSTRACT FROM AUTHOR]

The most common railway ballast is produced by quarrying, and its mechanical characteristics are crucial for both stability and drainage for safer and faster rail operations. Ballasted tracks have certain drawbacks, primarily because ballast starts to degrade over time. In this regard, reducing the rate of ballast degradation is vital to enhance track longevity and minimise maintenance costs. This study demonstrates how segments of huge waste rubber tyres (e.g., 3 m in diameter) from the mining industry can be used to improve the stability of tracks, while contributing to reduced ballast deformation and degradation. By placing arched segments cut from these tyres along the track shoulders beyond the edge of sleepers (i.e., the plan view gives a schematic impression of a caterpillar), the in-situ lateral confining pressure can be increased from 20–25 (standard track) to 40–50 kPa. This novel idea of confined-caterpillar track (CCT) was tested at a prototype physical model (1:1 scale) at the National Facility for the Heavy-haul Railroad Testing, and the experimental outcomes were compared with the performance of a conventional track. Apart from constributing to at least 25% saving of quarried aggregates, the test results prove that the CCT concept can curtail the lateral displacement and settlement of the ballast layer, while reducing particle breakage and affecting significant stress reduction in the underlying substructure layers. [ABSTRACT FROM AUTHOR]

Using solar photovoltaic power sources has become a discussed topic in the construction and energy industry. The pressing need to reduce reliance on fossil fuels, increasing costs of traditional electricity generation, and affording photovoltaic modules has sparked a growing interest in solar photovoltaics. This study aims to optimis e the layout of solar photovoltaic systems to minimise environmental impact and building load, comparing the performing south-oriented panels with east-west-oriented panels. The comprehensive analysis performed hinges on a diverse array of determinative factors that demand thoughtful consideration before embarking upon implementing any photovoltaic installation. These salient factors, including but not limited to structural integrity, incorporating ballast for stability enhancement, integrating requisite electrical components, selecting solar panels, quantifying energy production capabilities, assessing carbon emissions, and discerning associated benefits, require thoughtful consideration before implementing any photovoltaic installation. The findings derived from this study underscore that, within the context of the given geographical location, the solar photovoltaic system configured with an East-West orientation represents the optimal choice to reduce both emissions and structural load. This study provides a scientific basis for the construction industry and the energy field and guides the future development of photovoltaic installation projects in a more economic and environmentally friendly direction. [ABSTRACT FROM AUTHOR]

Copyright of Dicle University Journal of Engineering / Dicle Üniversitesi Mühendislik Dergisi is the property of Dicle Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ballast behaviour has a profound impact on global track performance and durability, particularly for turnouts where dynamic forces are substantial. As ballast is a discontinuous material, this paper proposes the application of a Discrete Element Method (DEM) to model its behaviour under a conventional track turnout, a new approach that has not yet been tried for turnouts, only for main tracks. The model was validated with real vertical stiffness data measured in an actual turnout and used to analyse ballast behaviour under dynamic traffic loads. The results show remarkable differences in ballast behaviour for train speeds close to 180 km/h, as particle interactions and stress levels extend to the entire ballast layer. At lower speeds, the stress under the sleeper forms a trapezoidal shape for a given cross-section, while the rest of the layer remains barely affected. Overall, the DEM model is a reliable tool for simulating ballast behaviour and provides new insights into ballast-turnout interactions, which may help improve maintenance in these essential track elements.

Understanding fundamental track behaviors under dynamic load conditions is important to optimize design practices and achieve high-quality track performance. The American Railway Engineering and Maintenance-of-Way Association provides recommended practices to estimate trackbed pressures, which are primarily based on the Talbot equations. The Talbot methodology for computing crosstie-ballast (CT-B) interfacial pressures may "not" be valid for modern railroad design due to several factors, including the sensitivity of pressure measuring equipment, the presence of uneven support conditions, and the implementation of jointed rails in testing different wheel loadings, which contributed to overestimation of pressure readings as a result of impact loading. However, modern railroad infrastructure has been designed with a smooth track layout and well-supported rails as well as incorporating rolling stock equipped with smooth wheels, particularly in high-speed train operations. This study proposes a new approach to estimate the pressures at the CT-B interface, which was developed using measured in-track CT-B interfacial pressures taken from an active mainline. The data from the in-track measurements were filtered by using a signal processing tool and analyzed to develop basic equations to predict interfacial pressures as a function of basic train characteristics, including train speed, wheel loads, and wheel spacing, assuming no impact loading from wheel defects. To validate the efficacy of the square wave theory, the predicted pressures were compared with the data obtained from in-track tests. Further, a method to estimate dynamic pressures of a moving train at the CT-B interface was developed using square wave theory. By representing the vehicles of a train as a periodic square waveform, the dynamic CT-B interfacial pressures can be predicted for an unlimited number of locomotives and cars for smooth track geometry, smooth wheels, limited rail surface roughness, and well-supported track. [ABSTRACT FROM AUTHOR]

Contact tests on machined and natural granite showed that extensive plastic deformation which extends to the core shape is happening before the cross-over from the behaviour of an elastic rough surface to the Hertzian behaviour of an elastic smooth contact when all asperities have yielded in the surface. The plastic deformation, which was found to take place when the estimated maximum stresses at the contact reaches about 0.6 of the material hardness, affects the behaviour during normal loading as the material will start to deform at constant stiffness after reaching these stresses. The plastic deformation during lateral loading also affects the applicability of lateral loading models. The data yielded a much lower lateral stiffness which is around one order of magnitude less than that predicted by the available contact models. [ABSTRACT FROM AUTHOR]

The theoretical and practical studies of the cyclic loads resulting from the movement and passage of trains on the unsaturated subgrade to determine the effect of the degree of saturation and moisture content on the foundations and infrastructure of the railway lines, especially the settlement in the railway lines as a result of the development of the train loads. Thirty-six laboratory experiments were carried out using models that simulate a railway with nearly half the scale of the real one, using an iron box of (1.5 × 1.0 × 1.0) meters and a layer of clay soil with a thickness of 0.5 m representing the base layer, were constructed inside it. Above it, there is a layer of crushed stone representing a 0.2 m thick ballast, topped by a rail line of 0.8 m long installed on three sleeper beams with dimensions of 0.9 m (0.1 × 0.1 m). The subgrade layer has been constructed at different saturation degrees as follows: 100, 80, 70, and 60%. The tests were carried out using different load amplitudes and frequencies. These experiments investigated the effect of the subgrade degree of saturation on the value of the stresses generated on the surface and the middle (vertical and lateral stresses) and the settlement of the subgrade. In the case of unsaturated subgrade soil, an increase in load frequency has a clear effect on increasing the generated stresses in the subgrade layer, especially with lower saturation levels. However, the results and measurements of these experiments found that the load frequency almost had no effect on the values of the stresses generated on the surface and inside the subgrade layer with a 100% degree of saturation. The results of the investigation demonstrated that, while load frequency had a minimal effect on track-panel settlement, it increased with the load amplitude and subgrade soil saturation degree. The change of settlement of the track panel with the number of cycles has a high rate at the beginning; after a while from that, it decreases gradually until, after some value of the number of cycles, the settlement changes at a very low rate and gradually. [ABSTRACT FROM AUTHOR]

In order to study the influence of an unsupported sleeper on the vertical bearing characteristics of heavy-haul railway ballast, a three-dimensional discrete element model (DEM) was established for a ballasted track, by removing ballast particles that come into contact with the bottom of the sleeper from the model to simulate the unsupported sleeper. Vertical bearing characteristics for ballast on different types of unsupported sleepers were studied. The results showed that an unsupported sleeper could reduce the bearing area of the ballast below the sleeper and reduce the number of ballast particles that were in contact. It could also lead to an increase in the maximum contact force between the particles, accelerating the deterioration of the particles (thus affecting the overall performance of the ballast) and reducing the vertical stiffness of the ballast. As the unsupported length and width increased, vertical stiffness gradually decreased. The vertical ballast stiffness for an unsupported sleeper was then used in a dynamic coupled vehicle/track model, and the effect of the unsupported sleeper on wheel/rail interaction was analyzed. Results showed that increasing the unsupported length and width leads to a decrease in the supporting force on the unsupported sleeper and to an increase in the supporting force on the adjacent sleepers. [ABSTRACT FROM AUTHOR]

Using solar photovoltaic power sources has become a discussed topic in the construction and energy industry. The pressing need to reduce reliance on fossil fuels, increasing costs of traditional electricity generation, and affording photovoltaic modules has sparked a growing interest in solar photovoltaics. This study aims to optimis e the layout of solar photovoltaic systems to minimise environmental impact and building load, comparing the performing south-oriented panels with east-west-oriented panels. The comprehensive analysis performed hinges on a diverse array of determinative factors that demand thoughtful consideration before embarking upon implementing any photovoltaic installation. These salient factors, including but not limited to structural integrity, incorporating ballast for stability enhancement, integrating requisite electrical components, selecting solar panels, quantifying energy production capabilities, assessing carbon emissions, and discerning associated benefits, require thoughtful consideration before implementing any photovoltaic installation. The findings derived from this study underscore that, within the context of the given geographical location, the solar photovoltaic system configured with an East-West orientation represents the optimal choice to reduce both emissions and structural load. This study provides a scientific basis for the construction industry and the energy field and guides the future development of photovoltaic installation projects in a more economic and environmentally friendly direction.

The railway is one of the cheapest methods to transport people and heavy goods. It is safer than highways. In Iraq, many railways connect the south country with the middle and north, which are old, damaged, and need to continued maintenance. Iraq needs to construct new lines of the rail track with low-cost, less maintenance, and highly stable structure, which requires understanding the behavior of rail track under train loads and the pattern of distribution of deformations, stresses, and strains inside the body of rail track and know the layer which more effected by changing the strength of ballast layer by change modulus of elasticity of it. This paper investigates the influence of modulus of elasticity of the ballast layer on the behavior of railways and the positions of deformation, stresses, and strains in the rail track which is most affected by the change in the modulus of elasticity and the value of the effect. The finite element approach was considered in this study using Abaqus Ver. 6.14-4 program. The investigation outcomes displayed that when the ballast layer’s modulus of elasticity E increase by 100 MPa, the value of deformation in the rail track is affected in all layers, and the value of decreased is 6.8 % for rail, 6.9 % for ballast, and 6.7 % for the sub-ballast layer. Therefore the strain of the sub-ballast layer is affected by the change modulus of elasticity of the ballast layer more than other ballast and subgrade. Also, the result shows that stresses in the rail are the only part of the rail track affected by the change in the ballast layer’s modulus of elasticity E, while the other layers are unaffected. So the increase in E of the ballast layer affects the layer beneath it, which is the sub-ballast layer.

Impact loads can exacerbate the deterioration and deformation of railway ballast, leading to changes in the mechanical properties of the track bed. Geogrid and rubber granules (RG) have been widely used in research to enhance the performance of ballast, however, the effects and mechanisms of these two materials working together are not yet clear. Therefore, in this study, a series of drop hammer impact tests were carried out on ballast aggregates with geogrids and RG. The tests were set up with different geogrid placement locations and RG contents on rigid and flexible subgrades. During the tests, the deformation, impact force and impact time of specimens were measured and recorded, the ballast specimens were sieved after the tests to investigate the breakage of the ballast, and the mechanical properties of the ballast specimens were analyzed after the impact using stiffness and damping ratio. It was found that the deformation and breakage of ballast specimens were significantly reduced by the combination of geogrid and RG, which was better than the geogrid or RG alone, and that the RG improved the damping ratio of ballast, while the geogrid reduced the reduction of stiffness of ballast caused by the addition of RG. Comparing and analyzing the results of each group of tests, the study confirmed that RG with 10% by volume and geogrid placed at 100 mm from the subgrade were the best combination to enhance the ballast performance. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A high-quality railway track resting on an excellent foundation is required to support high-speed railway transportation. The foundations of high-speed railway tracks are generally constructed on the lifted embankment with the improved ground using different reinforcement agents like geosynthetics and rigid lateral support. The present study performed dynamic finite element simulations on a ballasted rail track laid over a geosynthetically reinforced embankment with and without facing wall support. Three foundation geometries were analyzed to examine the effect of facing wall support and geosynthetics on the lateral resistance of the foundation. An area loaded with a constant pressure was moved at a constant speed, causing the load motion at different speeds in the 90-360 km/h range. Different parameters were calculated at node paths to help understand the lateral effect of moving load. The results showed that the lateral resistance based on nodal acceleration and velocity increased with facing wall support in the range of 40%-57%. Any increment over the minimum facing wall thickness of 300 mm does not significantly increase lateral resistance. Geosynthetics provided a vital function in the foundations with a less bulk volume of soil and increased the lateral resistance by 10%. [ABSTRACT FROM AUTHOR]

In the railways sector environmental concerns are growing, and many state-owned holding companies are investigating which is the best superstructure solution from the environmental point of view. In this regards, in the last years some companies have proposed ballastless systems, to reduce the replacement and maintenance activities and increase the reliability of the solution. Nevertheless, some environmental discussion emerged, even bearing in mind of different reference service lives.This study aims at comparing from an environmental point of view a ballasted and ballastless solutions using Life Cycle Assessment, by considering a declared unit of 1 km of railways infrastructure located in Italy. Results show the ballastless system has, on the contrary of previous studies, the lower environmental impact, due to its extended shelf life (90years) and low maintenance activities if compared with a ballasted one. Considering the same timeframe, the ballastless system has about halved impact on climate change (3.33E+06 kg CO2eq) compared to the ballasted one (1.75E+06 kg CO2eq). A sensitivity analysis has been carried out to consider possible variations in reference service life, transports and interval of rails substitution.

The article solves the problem of theoretically determining the deformable characteristics of railway ballast, considering its condition through mathematical modeling. Different tasks require mathematical models with different levels of detail of certain elements. After a certain limit, excessive detailing only worsens the quality of the model. Therefore, for many problems of the interaction between the track and the rolling stock, it is sufficient to describe the ballast as a homogeneous isotropic layer with a vertical elastic deformation. The elastic deformation of the ballast is formed by the deviation of individual elements; the ballast may have pollutants, the ballast may have places with different levels of compaction, etc. To be able to determine the general characteristics of the layer, a dynamic model of the stress–strain state of the system based on the dynamic problem of the theory of elasticity is applied. The reaction of the ballast to the dynamic load is modeled through the passage of elastic deformation waves. The given results can be applied in the models of the railway track in the other direction as initial data regarding the ballast layer.

From the perspective of the ballast railway track lateral stability, the sleeper-to-ballast interface has a vital role in the interaction between the sleeper and shoulder, crib, and base of the ballast layer. In this paper, ballast bulk density, vertical loading exerted by trains, and type of loading were considered as influencing factors on the variation of ballast components' contribution to the lateral resistance using the Discrete Element Method (DEM). For static tests, four vertical loadings of 0, 50, 100, and 150 kN, as well as three bulk densities of 1400, 1500, and 1600 kg/m3 of ballast, were prepared. For cyclic tests, four loading frequencies of 5, 10, 20, and 30 Hz were considered for a panel with a constant bulk density of 1500 kg/m3 subjected to 100 kN vertical loading. Simulations demonstrate that the lateral sleeper resistance is maximum when the ballast bulk density is approximately 1500 kg/m3. [ABSTRACT FROM AUTHOR]

Copyright of Materiały Budowlane is the property of Wydawnictwo SIGMA-NOT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The theoretical and practical studies of the cyclic loads resulting from the movement and passage of trains on the unsaturated subgrade to determine the effect of the degree of saturation and moisture content on the foundations and infrastructure of the railway lines, especially the settlement in the railway lines as a result of the development of the train loads. Thirty-six laboratory experiments were carried out using models that simulate a railway with nearly half the scale of the real one, using an iron box of (1.5 × 1.0 × 1.0) meters and a layer of clay soil with a thickness of 0.5 m representing the base layer, were constructed inside it. Above it, there is a layer of crushed stone representing a 0.2 m thick ballast, topped by a rail line of 0.8 m long installed on three sleeper beams with dimensions of 0.9 m (0.1 × 0.1 m). The subgrade layer has been constructed at different saturation degrees as follows: 100, 80, 70, and 60%. The tests were carried out using different load amplitudes and frequencies. These experiments investigated the effect of the subgrade degree of saturation on the value of the stresses generated on the surface and the middle (vertical and lateral stresses) and the settlement of the subgrade. In the case of unsaturated subgrade soil, an increase in load frequency has a clear effect on increasing the generated stresses in the subgrade layer, especially with lower saturation levels. However, the results and measurements of these experiments found that the load frequency almost had no effect on the values of the stresses generated on the surface and inside the subgrade layer with a 100% degree of saturation. The results of the investigation demonstrated that, while load frequency had a minimal effect on track-panel settlement, it increased with the load amplitude and subgrade soil saturation degree. The change of settlement of the track panel with the number of cycles has a high rate at the beginning; after a while from that, it decreases gradually until, after some value of the number of cycles, the settlement changes at a very low rate and gradually.

In order to study the influence of an unsupported sleeper on the vertical bearing characteristics of heavy-haul railway ballast, a three-dimensional discrete element model (DEM) was established for a ballasted track, by removing ballast particles that come into contact with the bottom of the sleeper from the model to simulate the unsupported sleeper. Vertical bearing characteristics for ballast on different types of unsupported sleepers were studied. The results showed that an unsupported sleeper could reduce the bearing area of the ballast below the sleeper and reduce the number of ballast particles that were in contact. It could also lead to an increase in the maximum contact force between the particles, accelerating the deterioration of the particles (thus affecting the overall performance of the ballast) and reducing the vertical stiffness of the ballast. As the unsupported length and width increased, vertical stiffness gradually decreased. The vertical ballast stiffness for an unsupported sleeper was then used in a dynamic coupled vehicle/track model, and the effect of the unsupported sleeper on wheel/rail interaction was analyzed. Results showed that increasing the unsupported length and width leads to a decrease in the supporting force on the unsupported sleeper and to an increase in the supporting force on the adjacent sleepers.

A high-quality railway track resting on an excellent foundation is required to support high-speed railway transportation. The foundations of high-speed railway tracks are generally constructed on the lifted embankment with the improved ground using different reinforcement agents like geosynthetics and rigid lateral support. The present study performed dynamic finite element simulations on a ballasted rail track laid over a geosynthetically reinforced embankment with and without facing wall support. Three foundation geometries were analyzed to examine the effect of facing wall support and geosynthetics on the lateral resistance of the foundation. An area loaded with a constant pressure was moved at a constant speed, causing the load motion at different speeds in the 90–360 km/h range. Different parameters were calculated at node paths to help understand the lateral effect of moving load. The results showed that the lateral resistance based on nodal acceleration and velocity increased with facing wall support in the range of 40%–57%. Any increment over the minimum facing wall thickness of 300 mm does not significantly increase lateral resistance. Geosynthetics provided a vital function in the foundations with a less bulk volume of soil and increased the lateral resistance by 10%.

Excessive crosstie wear and abrasion and ballast wear and fouling are fundamental problems contributing to inadequate railroad track performance. This adversely affects the attainment and long-term maintenance of desired track geometric requirements. The magnitudes and distribution of the stresses at the crosstie-ballast (CT-B) interface must be known to determine the stress distribution on and within the ballast. However, the track design recommendations to determine these pressures, which are largely based on a methodology from the 1980s, are currently valid for modern-day railroad applications for multiple reasons discussed in this study. This study analyzed CT-B interfacial pressure data measured on an active freight mainline in Mascot, Tennessee. Dynamic contact pressures at the CT-B interface were measured using hydraulic earth pressure cells for various wheel loads and train speeds. The test train was a Federal Railroad Administration (FRA) test train consisting of a diesel electric locomotive, a test car that had different wheel loads based on the deployable axle load, and an inspection car. Although the maximum train speed was limited to 64 km=h, this research found that speed variation has a minimal effect on the CT-B interfacial pressures. From the measured data, a Gaussian stress distribution equation is proposed to determine longitudinal pressure distribution transmitted to the CT-B interface for static conditions. In addition, the stress distribution along the length of a crosstie was investigated via laboratory experimentation using a half-length crosstie. As a result of the experimentation, a dimensionless trilinear approximation was developed to estimate the stress distribution along the length of the crosstie. In general, this research recommends that the longitudinal and lateral stress distributions be considered together to design a better railroad track. [ABSTRACT FROM AUTHOR]

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The properties of fresh ballasts collected from five quarries around Thailand were investigated in the laboratory. The investigation includes properties specified by the State Railway of Thailand (SRT) for ballast, i.e., rock type, sieve analysis, flat and elongation, and Los Angeles abrasion. Furthermore, cementing value, water absorption, specific gravity, sulfate soundness, and petrographic analysis were also conducted. The obtained rock properties were then compared with the requirements for use as a ballast specified by various national standards, including the Australian Rail Track Corporation (ARTC), the American Railway Engineering and Maintenance of Way Association (AREMA), and the State Railway of Thailand (SRT). The results show that all rocks generally comply with all standards. However, Buriram basalt is considered the best. Saraburi limestone has low abrasion resistance and high cementing value due to its carbonate nature which tends to give higher cementing strength. Igneous and metamorphic rocks usually have plagioclase as their parent mineral which gives low cementing potential. A large abundance of plagioclase in igneous rock, such as Buriram basalt, Nakhon Sawan dacite, and Prachinburi andesite, results in lower cementing values. Rock with high cementing value may hinder its usage as a railway ballast; therefore, the cementation property of ballast by cementing value test, initially suggested by Raymond [1], is strongly recommended as additional criterion in the selection of a ballast. [ABSTRACT FROM AUTHOR]

Simple Summary: Transoceanic shipping and global development of aquaculture are the main vectors for the introduction of marine organisms, as adults or their larvae, to new remote locations. Recent invasions by large species may be well known and documented, while older and smaller-bodied invasions are often hidden and more difficult to detect. In the present study, we investigated, using molecular methods, marine worms that bore into the shells of commercial molluscs on four continents. We have identified them as Polydora hoplura, a species originally described from Italy. The highest genetic diversity was detected in South African population. While high genetic diversity is often regarded as indicative of a species' natural range, our analysis of the worldwide discovery of P. hoplura calls into question its natural distribution in South Africa. The high genetic diversity of P. hoplura in this region may be the result of a complex dispersal history by ships and aquaculture. We tentatively propose the Northwest Pacific, or at the most the Indo–West Pacific, as its home region, not the Atlantic Ocean or the Eastern Pacific Ocean, and call for further exploration of this hypothesis. The spionid polychaete Polydora hoplura Claparède, 1868 is a shell borer widely occurring across the world and considered introduced in many areas. It was originally described in the Gulf of Naples, Italy. Adult diagnostic features are the palps with black bands, prostomium weakly incised anteriorly, caruncle extending to the end of chaetiger 3, short occipital antenna, and heavy sickle-shaped spines in the posterior notopodia. The Bayesian inference analysis of sequence data of four gene fragments (2369 bp in total) of the mitochondrial 16S rDNA, nuclear 18S, 28S rDNA and Histone 3 has shown that worms with these morphological features from the Mediterranean, northern Europe, Brazil, South Africa, Australia, Republic of Korea, Japan and California are genetically identical, form a well-supported clade, and can be considered conspecific. The genetic analysis of a 16S dataset detected 15 haplotypes of this species, 10 of which occur only in South Africa. Despite the high genetic diversity of P. hoplura in South Africa, we tentatively propose the Northwest Pacific, or at the most the Indo–West Pacific, as its home region, not the Atlantic Ocean or the Eastern Pacific Ocean. The history of the discovery of P. hoplura around the world appears to be intimately linked to global shipping commencing in the mid-19th century, followed by the advent of the global movement of commercial shellfish (especially the Pacific oyster Magallana gigas) in the 20th century, interlaced with continued, complex dispersal by vessels and aquaculture. Given that P. hoplura has been detected in only a few of the 17 countries where Pacific oysters have been established, we predict that it may already be present in many more regions. As global connectivity through world trade continues to increase, it is likely that novel populations of P. hoplura will continue to emerge. [ABSTRACT FROM AUTHOR]