Search Results (15)

By critically reviewing pseudo-static methods, it is demonstrated that approximating the earth pressure on a short heel’s vertical face (V-plane) using the Rankine solution for long-heel walls induces a negligible error. A finite element analysis is deployed to validate the pseudo-static results, with dynamic simulations incorporating 1–5 Hz sinusoidal seismic excitations to probe the resonance effects. The key results show that disregarding the impact of layered backfill placement on the initial stress states leads to non-conservative estimates of active earth pressure. Furthermore, the point of application of earth pressure rises significantly during strong shaking, and although the transient safety factors against sliding and overturning may fall below 1.0 during seismic events, the residual deformation analysis suggests that this does not necessarily lead to collapse. A significant amplification of bending moments and greater reductions in post-earthquake safety factors occur when the input frequency approaches the natural frequency of a wall. Finally, the paper proposes resonance prevention strategies for the seismic design of cantilever retaining walls, a methodology incorporating construction effects into the initial stress field modeling, and recommendations for selecting effective safety factors. Full article

As an important traffic and transportation roadway, tunnel engineering is widely used in important fields such as highways, railways, water conservancy, subways and mining. It is limited by complex geological conditions, harsh construction environments and poor robustness of the monitoring system. If the construction process and monitoring method are not properly designed, it will often directly induce disasters such as tunnel deformation, collapse, leakage and rockburst. This seriously threatens the safety of tunnel construction and operation and the protection of the regional ecological environment. Therefore, based on distributed fiber optic sensing technology, the full–cycle spatiotemporally continuous sensing information of the tunnel structure is obtained in real time. Accordingly, the health status of the tunnel is dynamically grasped, which is of great significance to ensure the intrinsic safety of the whole life cycle for the tunnel project. Firstly, this manuscript systematically sorts out the development and evolution process of the theory and technology of structural health monitoring in tunnel engineering. The scope of application, advantages and disadvantages of mainstream tunnel engineering monitoring equipment and main optical fiber technology are compared and analyzed from the two dimensions of equipment and technology. This provides a new path for clarifying the key points and difficulties of tunnel engineering monitoring. Secondly, the mechanism of action of four typical optical fiber sensing technologies and their application in tunnel engineering are introduced in detail. On this basis, a spatiotemporal continuous perception method for tunnel engineering based on DFOS is proposed. It provides new ideas for safety monitoring and early warning of tunnel engineering structures throughout the life cycle. Finally, a high–speed rail tunnel in northern China is used as the research object to carry out tunnel structure health monitoring. The dynamic changes in the average strain of the tunnel section measurement points during the pouring and curing period and the backfilling period are compared. The force deformation characteristics of different positions of tunnels in different periods have been mastered. Accordingly, scientific guidance is provided for the dynamic adjustment of tunnel engineering construction plans and disaster emergency prevention and control. At the same time, in view of the development and upgrading of new sensors, large models and support processes, an innovative tunnel engineering monitoring method integrating “acoustic, optical and electromagnetic” model is proposed, combining with various machine learning algorithms to train the long–term monitoring data of tunnel engineering. Based on this, a risk assessment model for potential hazards in tunnel engineering is developed. Thus, the potential and disaster effects of future disasters in tunnel engineering are predicted, and the level of disaster prevention, mitigation and relief of tunnel engineering is continuously improved. Full article

The stability of a backfill roof is critical to ensure safe production in underhand drift-and-fill mining. In this method, the basket weave drift layout is widely accepted. However, there is currently limited research on the displacement distribution and strength requirement of the backfill roof with this drift layout. To address the gap, a three-dimensional numerical model was established with FLAC3D, with the Maoping Lead–Zinc Mine as the engineering background, to investigate the stability of a backfill roof with the basket weave drift layout. In numerical simulations, an iterative search method was applied to determine the strength requirements of the backfill roof. The results show that the displacement of the backfill roof with the basket weave drift layout shows columnar or strip-like distribution patterns. The strength requirements (unconfined compressive strength) of the backfill roof in limited equilibrium for drift sizes of 3.5 m × 3.0 m, 4.5 m × 4.0 m, and 5.5 m × 5.0 m were determined to be 1.34 MPa, 1.57 MPa, and 2.38 MPa, respectively. A comparison was also made between the strength requirement predicted by traditional analytical solutions and those obtained from numerical simulations, which shows that traditional solutions tend to yield conservative results. The method and analysis process employed in this study can provide valuable references for backfill strength design in mines using underhand drift-and-fill mining. Full article

Earth–Air Heat Exchange (EAHE) systems are an eco-friendly and energy-efficient technology as pre-heating or pre-cooling systems in civil buildings. Technically, the performance of the EAHE system is influenced by properties associated with the technology. In this paper, the focus is placed on the properties covered by the published literature to understand how they impact the efficiency of these systems. The review scrutinizes the implication of pipe properties such as the material type (steel, Polyvinyl Chloride [PVC], concrete, or high-density polyethylene), diameter and length, and depth in the context of modern building design and energy conservation. Other properties considered in this work are air velocity and the bonding of pipes with the soil. The EAHE systems’ performance is not significantly influenced by the pipe material, unlike the pipe length and diameter. It is reported that longer pipes enhance the cooling output in the EAHE system. The pipe length positively correlates with the in-pipe air temperature. An increment in the pipe diameter led to a drop in the in-pipe air temperature. An indicative report states that an increasing air flow velocity can lead to thermal losses from pipes to their surrounding soil. The addition of sand below and above the pipe enhances the thermal conductivity, just as an increase in the moisture content of the soil will contribute. There are attempts to use additives, construction waste, graphite, and fly ash as a backfill material, but with opposing economic feasibility. Construction waste could help the EAHE system to improve by 80%. A combination of graphite and fly ash as a backfill material is cost-effective. Research on the pipe material type and standards development are limited. Overall, the pipe material type and length to adopt for an EAHE system are based on the funds’ availability for the construction. Full article

The construction of steel sheet pile cofferdams is a systematic project. Simplified construction sequences are widely used to facilitate the numerical modeling of cofferdams, while the mechanical behaviors of cofferdams with different construction sequences have yet to be understood. In the present study, finite element models of steel sheet pile cofferdams with different construction sequences were established, based on the temporary cofferdam of the Shenzhen–Zhongshan Link. The mechanisms of simplified construction sequences on bending moment were revealed by analyzing the displacements and contact press of steel sheet piles. The distribution of bending moment with elevation demonstrates the importance of the layered backfill process in numerical modeling. In addition, a finite element model of the cofferdam considering steady-state seepage was also established. The comparison of the hydrostatic pressure results and the bending moment results obtained by engineering experience and seepage analysis were discussed. The analysis results showed that the empirical method overestimated the maximum bending moment of the inner side of piles, which led to a more conservative design of the cofferdam. This work can serve as a reference for numerical modeling of steel sheet pile cofferdams and contribute to risk assessment in related engineering projects. Full article

The backfill binder material is the key to the cost and performance of cemented paste backfill. This study aims to understand the current situation of metal ore backfill binders, identify industry challenges, inspire research ideas, and explore development directions. Current research investigates trends and developments of backfill binders through literature review, experience summary, field research, statistical analysis, and other methods. Firstly, the main backfill binder types are summarized, including cement, metallurgical slag, thermal slag, chemical slag, and tailings binders. Secondly, the research progress regarding reactivity activation, hydration mechanism, harmful ion solidification, energy conservation, and carbon reduction is summarized. Thirdly, three industrial applications of new backfill binders are introduced and summarized. Cement is still the most common, followed by slag powder binder. The cases of steel slag binder and semi-hydrated phosphogypsum backfill have shown significant effects. Solid waste-based backfill binder materials are gradually replacing cement, which is a trend. Finally, further research is discussed, including hydration modeling and simulation, material properties under extreme environments, hardening process control, and technical standards for backfill binders. This work provides a reference and basis for promoting green and efficient paste backfill and sustainable industry development. Full article

To achieve high-quality no-till seeding, a wing-shaped stubble-breaking device with excellent stubble-breaking performance was designed for maize stubble. A model of maize stubble was developed based on the Discrete Element Method (DEM) and verified through soil bin tests. The DEM model was used to optimize the design parameters of the device and to investigate the interaction between the blades and the maize stubble during the stubble-breaking process. Field experiments were conducted to evaluate the performance of the device. The results indicated that the DEM model was accurate; when the optimal design parameters of the wing-shaped stubble-breaking device were a 37° slide cutting angle, 31° pitching angle, and 50 mm wing width, the average torque was 41.26 N·m, the soil breakage rate was 85.68%, and the soil backfill rate was 71.65%; the wing-shaped stubble-breaking device could separate the inside and outside of the strip tillage area and cut maize stubbles and soil blocks twice, thus having excellent stubble-breaking performance. This study provided an effective and feasible method for designing stubble-breaking devices and studying the interaction between blades, soil, and roots, which improved soil tillage theory and was beneficial in promoting conservation tillage technology. Full article

The slope erosion in the distribution area of completely weathered granite is often relatively severe, causing serious ecological damage and property loss. Ecological restoration is the most effective means of soil erosion control. Taking completely weathered granite backfill soil as the research object, two types of slope protection plants, Vetiver grass and Pennisetum hydridum, were selected. We analyzed these two herbaceous plants’ soil reinforcement and slope protection effects through artificial planting experiments, indoor simulated rainfall experiments, and direct shear tests. The test results showed that the runoff and sediment production rates of the two herbaceous plant slopes were significantly lower than those of the bare slope, with the order of bare slope > Vetiver grass slope > Pennisetum hydridum slope. Compared with the bare slope, the cumulative sediment production of the Vetiver grass slope at 60 min decreased by 56.73–60.09%, and the Pennisetum hydridum slope decreased by 75.97–78.45%. The indoor direct shear test results showed that soil cohesion decreases with increasing water content. As the root content of Vetiver grass roots increases, soil cohesion first increases and then decreases, reaching a maximum value when the root content is 1.44%. As the root content of Pennisetum hydridum increases, soil cohesion increases. The internal friction angle increases slightly with increasing water content, while the root content does not significantly affect the internal friction angle. Therefore, the shear strength of soil decreases when the water content increases. The shear strength of the Vetiver grass root-soil composite reaches a peak at a root content of 1.44%, while the shear strength of the giant king grass root-soil composite increases as the root content increases. At the same root content, the shear strength of the Vetiver grass root-soil composite is slightly higher than that of giant king grass. The reinforcement effect of roots on shallow soil is better than on deep soil. Both herbaceous plants have an excellent soil-fixing and slope-protecting impact on the fully weathered granite backfill slope. Pennisetum hydridum’s soil and water conservation effect is significantly better than that of the Vetiver grass. In contrast, Vetiver grass roots slightly outperform Pennisetum hydridum in enhancing the shear strength of the soil. The research results can provide a theoretical basis for the vegetation slope protection treatment of fully weathered granite backfill slopes. Full article

This article addresses challenges in the design of underground high-voltage transmission lines, focusing on thermal management and cable ampacity determination. It introduces an innovative proposal that adjusts the dimensions of the backfill to enhance ampacity, contrasting with the conventional approach of increasing the core cable’s cross-sectional area. The methodology employs a particle swarm optimization (PSO) technique with adaptive penalization and restart strategies, implemented in MATLAB for parameter autoadaptation. The article emphasizes more efficient solutions than traditional PSO, showcasing improved convergence and precise results (success probability of 66.1%). While traditional PSO is 81% faster, the proposed PSO stands out for its accuracy. The inclusion of thermal backfill results in an 18.45% increase in cable ampacity, considering variations in soil thermal resistivity, backfill properties, and ambient temperature. Additionally, a sensitivity analysis was conducted, revealing conservative values that support the proposal’s robustness. This approach emerges as a crucial tool for underground installation, contributing to continuous ampacity improvement and highlighting its impact on decision making in energy systems. Full article

There is widespread enthusiasm toward utilizing mass timber panels (MTP), mainly cross-laminated timber (CLT), in construction, including for the basements of low-rise buildings. CLT is deemed a sustainable alternative to the widely used concrete foundation walls due to significant advantages such as less vulnerability to cracking due to uneven load distribution and presence of concentrated loads, higher thermal resistance, less construction time due to whole-wall prefabrication and installation, and less detrimental environmental effects. This study is part of an extensive research program aimed at developing the structural analysis and design concepts and methodology for constructing house foundation walls using MTPs, focusing on the usage of CLT. After comparison of CLT basements with their equivalent concrete ones from the sustainability point of view, and a brief discussion on geotechnical and hygrothermal considerations, the main theme of the article includes the structural analysis and design methodology, requirements, and the procedure to achieve a reliable and efficient design of a CLT basement. A simplified analysis procedure to design the laminate thicknesses and the number of layers in CLT foundation walls for different scenarios considering various variables such as soil type and backfill height is discussed, and results in the form of pre-engineered design tables are provided. The findings of this study demonstrate that, depending on the soil type and backfill height, 3–7-ply CLT panels would be needed for net wall heights of up to 3 m. Additionally, advanced finite element analyses are performed on sample architypes to validate the simplified analysis procedure used for design. It is shown that the proposed analysis procedure and the pre-engineered tables produce conservative and efficient results. Full article

High-performance computing comprises thousands of processing powers in order to deliver higher performance computation than a typical desktop computer or workstation in order to solve large problems in science, engineering, or business. The scheduling of these machines has an important impact on their performance. HPC’s job scheduling is intended to develop an operational strategy which utilises resources efficiently and avoids delays. An optimised schedule results in greater efficiency of the parallel machine. In addition, processes and network heterogeneity is another difficulty for the scheduling algorithm. Another problem for parallel job scheduling is user fairness. One of the issues in this field of study is providing a balanced schedule that enhances efficiency and user fairness. ROA-CONS is a new job scheduling method proposed in this paper. It describes a new scheduling approach, which is a combination of an updated conservative backfilling approach further optimised by the raccoon optimisation algorithm. This algorithm also proposes a technique of selection that combines job waiting and response time optimisation with user fairness. It contributes to the development of a symmetrical schedule that increases user satisfaction and performance. In comparison with other well-known job scheduling algorithms, the simulation assesses the effectiveness of the proposed method. The results demonstrate that the proposed strategy offers improved schedules that reduce the overall system’s job waiting and response times. Full article

China has committed to peak its carbon emissions by 2030, which puts forward a new issue for underground metal mines—selecting a cleaner mining method which requires less energy and generates less carbon emissions. This paper proposes an enterprise-level model to estimate life-cycle energy consumption and carbon emissions, which takes more carbon sources (e.g., cement and carbon sink loss) into consideration to provide more comprehensive insights. Moreover, this model is integrated with the energy-conservation supply curve and the carbon abatement cost curve to involve production capacity utilization in the prediction of future performance. These two approaches are applied to 30 underground iron mines. The results show that (1) caving-based cases have lower energy consumption and carbon emissions, i.e., 673.64 GJ/kt ore, 52.21 GJ/kt ore (only considering electricity and fossil fuel), and 12.11 CO₂ eq/kt ore, as compared the backfilling-based cases, i.e., 710.08 GJ/kt ore, 63.70 GJ/kt ore, and 40.50 t CO₂ eq/kt ore; (2) caving-based cases present higher carbon-abatement potential (more than 12.95%) than the backfilling-based vases (less than 9.68%); (3) improving capacity utilization facilitates unit cost reduction to mitigate energy consumption and carbon emissions, and the energy-conservation and carbon-abatement potentials will be developed accordingly. Full article

To better protect the ecological environment during large scale underground coal mining operations in the northwest of China, the authors have proposed a water-conservation coal mining (WCCM) method. This case study demonstrated the successful application of WCCM in the Yu-Shen mining area. Firstly, by using the analytic hierarchy process (AHP), the influencing factors of WCCM were identified and the identification model with a multilevel structure was developed, to determine the weight of each influencing factor. Based on this, the five maps: overburden thickness contour, stratigraphic structure map, water-rich zoning map of aquifers, aquiclude thickness contour and coal seam thickness contour, were analyzed and determined. This formed the basis for studying WCCM in the mining area. Using the geological conditions of the Yu-Shen mining area, the features of caved zone, water conductive fractured zone (WCFZ) and protective zone were studied. The equations for calculating the height of the “three zones” were proposed. Considering the hydrogeological condition of Yu-Shen mining area, the criteria were put forward to evaluate the impact of coal mining on groundwater, which were then used to determine the distribution of different impact levels. Using strata control theory, the mechanism and applicability of WCCM methods, including height-restricted mining, (partial) backfill mining and narrow strip mining, together with the applicable zone of these methods, were analyzed and identified. Under the guidance of “two zoning” (zoning based on coal mining’s impact level on groundwater and zoning based on applicability of WCCM methods), the WCCM practice was carried out in Yu-Shen mining area. The research findings will provide theoretical and practical instruction for the WCCM in the northwest mining area of China, which is important to reduce the impact of mining on surface and groundwater. Full article

Water conservation in mining is the key to solving the conflict between coal resource exploitation and ecological environment protection, especially in arid and semi-arid mining areas. Continuous excavation and continuous backfilling (CECB) in longwall mining is an important method to realize water conservation mining. Considering the different boundary conditions of the main roof stress in different mining phases, the mechanical models of clamped–clamped beam, continuous beam, and elastic foundation beam among filling body, main roof, and strata are established. Furthermore, the spatio-temporal evolution mechanisms of mining-induced fractures (MIF) are studied. It is found that there is a hyperbolic function relationship between MIF and the mining roadway (MR) filling percentages. Based on mining the XV coal seam under CECB in the Wangtaipu Coal Mine, the distribution patterns of MIF are studied. It is concluded that the distribution pattern is an isosceles trapezoid with the moving angle of overlying strata as the bottom angle, and the upper and lower boundary of MIF as the two parallel sides. Based on the influence coefficient of MR filling percentages on MIF, the curve of the MIF height is divided into three ranges, which include the stability control range, the critical range, and the lost control range. The controlling effects of MR filling percentages are studied, and the calculation expression of the MIF height in the stability control range is given. In engineering practice, 90% MR filling percentage is used for CECB. The MIF height is about 3.0 times of mining height, and the main roof beam is not broken. The water-resisting property of aquiclude III is not destroyed, thus, the mining does not adversely impact the water. The results provide theories and practices for controlling MIF under CECB in the conditions of extremely close distance aquifers. Full article

The mining induced subsidence and strata deformation are likely to affect the stability of the aquiclude, resulting in loss of water resources in the mining area. In order to reduce the disturbance of coal mining to the overlying strata and to preserve the water resources in the coal mining area, the roadway backfill mining (RBM) method was trialed in Yuyang coal mine in Northern Shaanxi, China. Based on pressure arch theory and ultimate strength theory, a mechanical model was developed to analyze the stability of coal pillars. Then the maximum number of vacant roadways between the mining face and the backfilling face was determined according to the stability of coal pillar and filling body. The method to calculate aquiclude subsidence and deformation was also proposed. Furthermore, as indicated by FLAC3D numerical simulations, the maximum tensile stress subjected by the aquiclude was 0.14 MPa, which is smaller than its tensile strength; the horizontal deformation was 0.24 mm/m, which is also smaller than the critical deformation of failure. Field monitoring data demonstrated a maximum of 2.76 m groundwater level drop in the mining area after mining. The groundwater level was determined to be 4.45~10.83 m below surface, ensuring the normal growth of surface vegetation and realizing the water-conservation coal mining (WCCM). Full article