Search Results (22)

High-water material (HWM) is widely used for roadside filling in gob-side entry retaining (GER), where its creep behavior under sustained loading critically influences the long-term stability of the roadway. To enhance the long-term mechanical performance of HWM, this study modified it with polyethylene (PE) fiber and conducted uniaxial compression creep tests to investigate the effects of fiber content on time-dependent deformation, long-term strength, and failure time. The results indicate that when the applied stress remains below the long-term strength, the creep deformation of PE fiber-modified HWM stabilizes over time. In contrast, under higher stress levels, the deformation of HWM continuously develops over time and progresses through three stages: attenuation, steady-state, and accelerated creep, ultimately resulting in failure. Compared with pure HWM, the fiber-modified material exhibits a significant improvement in long-term strength, which increases linearly with fiber content. Furthermore, a higher fiber content raises the stress threshold for creep failure and substantially extends the time to failure. To predict the creep response of PE fiber-modified HWM, a viscoelastic-plastic creep damage model was developed using the component combination method, incorporating the Riemann–Liouville fractional-order integral operator and a time-dependent damage evolution equation. The reliability of the model was verified by utilizing the experimental data, and a sensitivity analysis of the model parameters was carried out based on the fitting results. The proposed model can not only describe the creep behavior of HWM across all loading stages, including the accelerated creep phase, but also accounts for the effect of fiber content on long-term strength. These findings can provide a theoretical foundation for the design and stability assessment of fiber-reinforced HWM roadside backfills in GER engineering. Full article

China’s roof-cutting and pressure relief gob-side entry retaining (RCPR-GER) technology provides an efficient non-pillar mining solution that significantly enhances coal recovery. This paper presents a systematic review of the technological progress in Chinese coal mines from 2011 to 2023, based on an analysis of 1038 publications from CNKI, EI, and Web of Science using VOS viewer and Origin software. Four main technical approaches are examined: gob-side entry retaining without roadside filling, with roadside filling, with roof-cutting and pressure relief, and hybrid methods. Five key roof-cutting techniques are evaluated: dense drilling, high-pressure water-jet slotting, hydraulic fracturing, blasting, presplitting, and roof water injection softening. Successful applications have been documented in coal seams with thicknesses of 1.6–6.15 m and burial depths of 92–1037 m, demonstrating wide adaptability. The roof-cutting short-beam theory underpins the mechanism, which reduces roadway deformation, shortens the cantilever beam length, and alters stress transfer paths. Compared to previous reviews on general gob-side entry retaining, this study offers a dedicated synthesis and comparative analysis of RCPR-GER technologies, establishing a selection framework grounded in geological compatibility and engineering practice. Future research should focus on adaptive parameter design for deep hard composite roofs, quantitative modeling of passive roof-cutting effects, optimization of cutting timing and orientation, and floor-heave control technologies to extend applications under complex geological conditions. Full article

Plant growth regulators (PGRs) are natural or synthetic substances that control and manipulate plant physiological processes, controlling branching and vegetative growth. Maintaining roadside vegetation through frequent mowing is costly, dangerous, and unsustainable. This narrative literature review proposes a revolution in this management by conducting a systematic literature review on the strategic application of PGRs on roadsides. Practices such as the application of plant growth regulators, the use of native cover crops, and bioengineering techniques with stabilizing species were analyzed. Previous studies have shown that the use of regulators such as mepiquat chloride and paclobutrazol reduces plant height and aboveground biomass, favoring growth control and compacting the plant architecture. The environmental and operational impacts related to vegetation control on roadside strips were also considered. Integrated with LiDAR technology for precise monitoring, this model establishes a new paradigm: smart, safe, and sustainable. Therefore, it is hoped that this compendium will fill a gap in national guidelines by offering an evidence-based protocol guideline for the use of PGR as an alternative to traditional management methods, thus reducing the number of mowing and weeding operations in highway right-of-way areas. Full article

The high stress environment and hard roof conditions seriously limit the application of gob-side roadway retaining. To achieve non-coal pillar mining, this study proposes a novel method combining roadside filling and roof cutting under stress-release and strong support synergy. Mechanical modeling reveals surrounding rock failure mechanisms in high-stress gob-side roadway retaining. Numerical simulations show the new method reduces surrounding rock stress/displacement more effectively than conventional gob-side roadway retaining. Optimized parameters were validated via field tests, confirming significant control of rock deformation under complex high-stress conditions. The method successfully enables non-coal pillar mining, providing a scientific basis for similar applications. Full article

In order to examine the fracture development law of overlying strata in goafs and to reasonably lay out a high gas-drainage roadway under gob-side entry retaining with roadside filling, the 91–105 working face of the Wangzhuang Coal Mine was selected as the engineering case study. The failure laws and fracture development characteristics of the overlying strata in both the strike and dip directions using gob-side entry retaining and roadside filling were studied through rock mechanic tests and PFC numerical simulations. The optimal layout of the high gas-drainage roadway was determined through theoretical analysis and coupled Fluent–PFC numerical simulations, and on-site monitoring was conducted to evaluate the extraction effects. The results indicate that the first weighting interval of the 91–105 working face was 40 m, while the periodic weighting interval was approximately 14 m. The height of the falling zone was 14.4 m, and the height of the gas-conducting fracture zone was 40.7 m. In the dip direction, compared with coal pillar retaining, gob-side entry retaining with roadside filling formed an inverted trapezoid secondary breaking zone above the retaining roadway. Using this method, the span of the separation zone increased to 30 m, and the collapse angle decreased to 52°, resulting in a shift in the separation zone—the primary space for gas migration—toward the goaf. It was determined that the optimal location of the high gas-drainage roadway was 28 m above the coal roof and 30 m horizontally from the return air roadway. Compared with the 8105 working face, this position was 10 m closer toward the goaf. On-site gas extraction monitoring data indicate that, at this optimized position, the gas concentration in the high gas-drainage roadway increased by 22%, and the net gas flow increased by 18%. Full article

To explore the control technology on surrounding rock of gob-side entry retaining (GSER) below a goaf in a near distance coal seam (NDCS), research was conducted on the floor ruin range, the floor stress distribution features, the layout of the GSER below near distance goaf, the width of the roadside filling wall (RFW), and the control technology of the GSER surrounding rock below the near distance goaf after upper coal seam (UCS) mining. The results show that (1) the stress of the goaf floor has obvious regional features, being divided into stress high value zone (Zone A), stress extremely low zone (Zone B), stress rebound zone (Zone C), stress transition zone (Zone D), and stress recovery zone (Zone E) according to different stress states. The stress distribution features at different depths below the goaf floor in each zone also have differences. (2) Arranging the roadway in Zone A below a coal pillar, the roadway is at high stress levels, which is not conducive to the stability of the surrounding rock. Arranging the roadway in Zone B below the goaf floor, the bearing capacity of the surrounding rock itself is weak, making it difficult to control the surrounding rock. Arranging the roadway in Zone C, the mechanical properties of the surrounding rock are good, and the difficulty of controlling the surrounding rock is relatively low. Arranging the roadway in Zone D and Zone E, there is a relatively small degree of stress concentration in the roadway rib. (3) When the RFW width is 0.5–1.5 m, stress concentration is more pronounced on the solid coal rib, and the overlying rock pressure is mainly borne by the solid coal rib, with less stress on the RFW. When the RFW width is 2~3 m, the stress on the RFW is enhanced, and the bearing capacity is significantly increased compared to RFW of 0.5–1.5 m width. The RFW contributes to supporting the overlying rock layers. (4) A comprehensive control technology for GSER surrounding rock in lower coal seam (LCS) has been proposed, which includes the grouting modification of coal and rock mass on the GSER roof, establishing a composite anchoring structure formed by utilizing bolts (cables); the strong support roof and control floor by one beam + three columns, reinforcing the RFW utilizing tie rods pre-tightening; and the hydraulic prop protection RFW and bolts (cables) protection roof at roadside. This technology has been successfully applied in field practice. Full article

In the realm of transportation system management, various remote sensing techniques have proven instrumental in enhancing safety, mobility, and overall resilience. Among these techniques, Light Detection and Ranging (LiDAR) has emerged as a prevalent method for object detection, facilitating the comprehensive monitoring of environmental and infrastructure assets in transportation environments. Currently, the application of Artificial Intelligence (AI)-based methods, particularly in the domain of semantic segmentation of 3D LiDAR point clouds by Deep Learning (DL) models, is a powerful method for supporting the management of both infrastructure and vegetation in road environments. In this context, there is a lack of open labeled datasets that are suitable for training Deep Neural Networks (DNNs) in transportation scenarios, so, to fill this gap, we introduce ROADSENSE (Road and Scenic Environment Simulation), an open-access 3D scene simulator that generates synthetic datasets with labeled point clouds. We assess its functionality by adapting and training a state-of-the-art DL-based semantic classifier, PointNet++, with synthetic data generated by both ROADSENSE and the well-known HELIOS++ (HEildelberg LiDAR Operations Simulator). To evaluate the resulting trained models, we apply both DNNs on real point clouds and demonstrate their effectiveness in both roadway and forest environments. While the differences are minor, the best mean intersection over union (MIoU) values for highway and national roads are over 77%, which are obtained with the DNN trained on HELIOS++ point clouds, and the best classification performance in forested areas is over 92%, which is obtained with the model trained on ROADSENSE point clouds. This work contributes information on a valuable tool for advancing DL applications in transportation scenarios, offering insights and solutions for improved road and roadside management. Full article

Against the background of the prevailing green development paradigm, numerous coal mines have embraced the adoption of gob-side entry retaining mining technology. The most commonly employed form of gob-side entry retaining involves building an artificial wall along the edge of the goaf behind the working face to maintain the roadway. The pivotal challenge in gob-side entry retaining lies in the roadside support. Currently, commonplace concrete serves as the predominant material for the roadside filling body. Nevertheless, traditional concrete exhibits drawbacks, including inadequate tensile strength and poor toughness, leading to wall cracks or even collapses in the retaining wall. Steel fiber, a frequently employed reinforcement and toughening agent in concrete, has found widespread application in the construction sector and other fields. However, its use as a roadside filling material in underground coal mines remains infrequent. Therefore, in this paper, the flow and mechanical properties of steel fiber concrete were tested and analyzed, and field industrial tests were conducted. Results of indoor experiments show that steel fibers reduce the slump of concrete. The addition of steel fibers shifted the pore compacting stage, linear elasticity stage, and destabilization stage forward and improved the post-peak bearing capacity. The addition of steel fibers makes the concrete compressive and tensile strength show a “first increase and then decrease” trend; both peaked at 1.5%, and the increase in tensile strength is more pronounced. Steel fibers enhance the strength of compressive strength of concrete at an early age, weaker at a late age, and tensile strength inversely. The addition of steel fiber can change the concrete matrix from tensile damage to shear damage, and the toughness index shows the trend of “first increase and then decrease”, and reaches the peak value when the dosage is 1.5%. Industrial test results show that steel fiber concrete as a roadside filling body can reduce the surrounding rock surface displacement and bolt (cable) force. Full article

The fully mechanized caving roadway’s floor heave has a significant impact on the stability of the narrow coal pillars, the filling body next to the roadway, as well as the entire roadway. Significant floor heave necessitates extensive maintenance and rebuilding work, which has a negative impact on the mine’s regular operations. The costs of sustaining and maintaining the roads are significantly increased by production. In this study, a mechanical model of the floor heave of the road along the goaf is established using the Winker elastic foundation theory model. The mechanical model of the floor heave of the roadway is confirmed when combined with engineering cases. The findings of the study indicate that there is almost no deformation of the side floor of the roadside support and the solid coal. The floor deformation of the roadway area exhibits non-positive symmetry and a “parabolic” characteristic. Roadway width, burial depth, and roadway floor heave all have linearly positive correlations, but elastic modulus of the floor, burial depth, and highway floor heave all have negatively exponential correlations. The maximum deformation of the floor heave, which has a maximum value of 628 mm, is close to the side of the roadway support body; the theoretical model’s maximum value for the floor heave after 100 days of actual deformation monitoring is 645 mm. Between the maximum value and the maximum value as measured, there is a 2.6% error. The paper has important guiding significance for explaining the mechanism of floor heave in goaf roadway and controlling the deformation of the roadway floor. Full article

Considering the factors affecting the surrounding rock stability of gob-side entry retaining, the applicability of a large-diameter, concrete-filled steel tube roadside support body in a top-coal caving fully mechanized face is discussed, and a new approach to gob-side entry retaining is proposed in this study. The mechanical model of the surrounding rock structure of gob-side entry retaining in a top-coal caving fully mechanized face was established, the critical state of column–roof contact shear slip instability was clarified through Prandtl foundation failure theory, and the deformation mechanism of the surrounding rock of the retained roadway was analyzed through numerical simulation. The results indicated that the range of the tensile stress zone and extreme tensile stress of the roof between columns are closely related to the spacing of columns, which is the key factor influencing the deformation of the retained roadway. In addition, besides uncontrollable factors, the stability of the contact interface between the roof and columns is directly related to the area of the contact interface between the concrete-filled steel tubes and the roof, and the size of the critical contact area is directly related to the properties of top-coal mass. Finally, a field test was carried out in 91–101 working panels in the Wang-Zhuang Coal Mine; the maximum convergence of the roof and floor was 510 mm, and the area of the retained roadway section reached 12.9 m², which is within a reasonable range. Full article

As the number of truck registrations and the traffic volume have increased continuously in urban areas, the problem of truck illegal parking on the roadside has become more serious in Korea. Although the government presented the necessity and the construction plan of the truck public parking lots through the ‘4th Comprehensive Plan for Expansion of Truck Resting Facilities’, there is no detailed guideline for the local government of where to construct them. The previous studies on the location selection of the parking lots have mainly focused on passenger cars and buses, but not trucks, and the process for candidate location selection was not mentioned. To fill this gap, this study presents a decision-making process for the location selection of truck public parking lots in urban areas based on mixed-integer programming; it includes a candidate location selection by spatial analysis and an optimal location determination by the application of the competitive p-median algorithm. A case study of Incheon was conducted to validate the presented decision-making process. This study introduced a systematic decision-making process that includes standards establishment, data processing, and methodology application; it is universalistic enough to be utilized as a guideline for the government to efficiently construct truck public parking lots. Full article

Previous studies have shown that climatic and anthropogenic factors influence the variations in the stable isotope signature of tree materials in an urban ecosystem. However, the responses of urban trees to various anthropogenic and precipitation interventions are unclear. To fill the research gap, the isotopic composition (δ¹⁵N and δ¹⁸O) and total nitrogen content of the soil-plant system of urban forests were measured, focusing on typical urban tree species (Populus tomentosa and Ficus virens). The research was done under various land uses in China’s Beijing and Shenzhen megacities (with different humidity conditions). The linear mixed-effect model revealed that the δ¹⁵N values in the leaves of roadside Ficus virens were significantly higher than those in urban park sites, away from the road (δ¹⁵N difference = 7.2‰). In contrast, Populus tomentosa leaves exhibited a non-significant difference (δ¹⁵N difference = −1.8‰). Further regression analysis revealed that the variations in δ¹⁵N in tree leaves could be attributed to the proximity to highways, suggesting the influence of vehicle exhaust on δ¹⁵N values in roadside trees. The linear mixed-effect model also revealed δ¹⁸O values significantly higher in Populus tomentosa leaves than in Ficus virens leaves. To assess the influence of humidity conditions on δ¹⁸O values in the leaves, the ratio of the atmospheric and intercellular vapor pressures (e_a/e_i) of tree canopies was estimated. The result revealed that the e_a/e_i of Ficus virens was significantly higher than for Populus tomentosa, ascribed to the variation in the humidity conditions of the two megacities. These results highlight that urban trees can potentially serve as bioindicators for atmospheric pollution and humidity. Our findings highlight the ecophysiological responses of urban forests related to N and O as they vary according to traffic exhaust and relative humidity. Consequently, they are potentially valuable indicators of urban atmospheric contamination, forming a nature-based solution for citizen welfare improvement. Full article

As a kind of non-coal pillar roadway support technique, gob-side entry retaining is of great significance to improve the production efficiency of a fully mechanized working face. However, the construction of the roadway is often subject to the surrounding rock conditions, the application is mainly concentrated in the nearly horizontal and gently inclined coal seam conditions, and the application in the steeply inclined coal seam conditions is relatively less. This paper is based on the gob-side entry retaining roadway construction of the 58^# upper right 3^# working face in the fifth district of Xinqiang Coal Mine, and describes the investigation in which we measured the advanced abutment stress, mining stress, and roof stress and analyzed the moving rule of roof. On this basis, in this work, we determined the filling parameters and process and investigated the filling effect from the perspective of the deformation of the filling body and the surrounding rock. The results show that the influence range of the advanced abutment stress in the working face is about 20~25 m, the stress in the upper part is intense, and stress in the middle and lower parts are relaxed. The setting load, the cycle-end resistance, and the time-weighted mean resistance at the upper end of working face along the direction of length are the largest, followed by the middle part, and the lower end is the minimum. When exploiting the steep inclined coal seam, the upper part of the working face is more active than the lower part, and the damaging range of overlaying strata is mainly in the upper part of the goaf. With this research, we established the filling mining process in steeply inclined coal seams and determined the relevant parameters. The gangue cement mortar filling can ensure the deformation of the filling body, the surrounding rock of the roadway is small in the process of roadway retention, and the stress of the filling body is also small, which ensure the successful retention of the roadway. This study verifies the possibility of repair-less exploitation and provides a reference for the popularization and application of the gob-side entry retaining technique in steep inclined coal seam. Full article

Sight distance is an important indicator to ensure the safety of drivers, and is also an indispensable evaluation basis in highway safety engineering. In mountainous highways, high slopes and small radius often lead to poor visibility and traffic accidents. Through the combined calculation of horizontal and vertical sections, this paper comprehensively considers the specific sizes of roadside clearance, high slope, as well as the position and height of the driver’s view point and other factors, and it analyzes the limited visibility of the driver in the process of driving right turn. An effective and simplified calculation method based on design data for three dimensional (3D) stopping sight distance (S.S.D.) in high fill sections is proposed. Finally, the S.S.D. inspection of the actual highway, based on design speed and operating speed, is carried out, and the sight distance of the calculated point is judged by comparing the value with the normal value and the calculation result of the horizontal sightline offset. The results show that the method proposed in this paper is consistent with the sight distance results obtained by the horizontal sightline offset method, which indicates the calculation method is accurate and provides a technical reference for S.S.D. evaluation in highway safety engineering. Full article

The Northern Territory Top End Health Service, Medical Entomology Section and the City of Darwin council carry out a joint Mosquito Engineering Program targeting the rectification of mosquito breeding sites in the City of Darwin, Northern Territory, Australia. In 2005, an investigation into potential subterranean stormwater breeding sites in the City of Darwin commenced, specifically targeting roadside stormwater side entry pits. There were 79 side entry pits randomly investigated for mosquito breeding in the Darwin suburbs of Nightcliff and Rapid Creek, with 69.6% of the pits containing water holding sumps, and 45.6% of those water holding sumps breeding endemic mosquitoes. Culex quinquefasciatus was the most common mosquito collected, accounting for 73% of all mosquito identifications, with the potential vector mosquito Aedes notoscriptus also recovered from a small number of sumps. The sumps were also considered potential dry season maintenance breeding sites for important exotic Aedes mosquitoes such as Aedes aegypti and Aedes albopictus, which are potential vectors of dengue, chickungunya and Zika virus. Overall, 1229 side entry pits were inspected in ten Darwin suburbs from 2005 to 2008, with 180 water holding sumps identified and rectified by concrete filling. Full article