Search Results (430)

It is well known that the operation of a Borehole Heat Exchanger (BHE) can thermally induce groundwater convection in aquifers, enhancing the thermal performance of the BHE. However, the effect on the thermal performance of BHEs installed in low-permeable rock formations remains unclear. In this study, two BHEs were installed in a silty sandstone formation, one backfilled with high-permeable materials and the other grouted with sand–bentonite slurry. A Thermal Response Test (TRT) showed that the fluid outlet temperature of the high-permeable-material backfilled BHE was about 2.5 °C lower than that of the BHE refilled with sand–bentonite slurry, implying a higher thermal efficiency. The interpreted borehole thermal parameters also show a lower borehole thermal resistance in the high-permeable-material backfilled BHE. Physical model tests reveal that groundwater convective flow was induced in the high-permeable-material backfilled BHE. A test of BHEs with different borehole diameters shows that the larger the borehole diameter, the higher the thermal efficiency is. Thus, the thermal performance enhancement was attributed to two factors. First, the induced groundwater flow accelerates heat transfer by convection. Additionally, the increment of the thermal volumetric capacity of the groundwater stored inside a high-permeable-material refilled borehole stabilized the borehole’s temperature, which is key to sustaining high thermal efficiency in a BHE. The thermal performance enhancement demonstrated here shows potential for reducing reliance on fossil-fuel-based energy resources in challenging geological settings, thereby contributing to developing more sustainable geothermal energy solutions. Further validation in diverse field conditions is recommended to generalize these findings. Full article

After the original support system in the auxiliary transportation roadway of the northern wing of the Zhaoxian Mine failed, the extent of damage and deformation varied significantly across different sections of the drift. A single support method could not meet the engineering requirements. Therefore, this paper conducted research on the classification of roadway damage and zoning repair. The overall damage characteristics of the roadway are described by three indicators: roadway deformation, development of rock mass fractures, and water seepage conditions. These are further refined into nine secondary indicators. In summary, a rock mass damage combination weighting evaluation model based on the FAHP–entropy weight TOPSIS method is proposed. According to this model, the degree of damage to the roadway is divided into five grades. After analyzing the damage conditions and support requirements at each grade, corresponding zoning repair plans are formulated by adjusting the parameters of bolts, cables, channel steel beams, and grouting materials. At the same time, the reliability of partition repair is verified using FLAC3D 6.0 numerical simulation software. Field monitoring results demonstrated that this approach not only met the support requirements for the roadway but also improved the utilization rate of support materials. This provides valuable guidance for the design of support systems for roadways with similar heterogeneous damage. Full article

Overburden isolated grouting injection is an efficient and green mining technology. During the filling process, fly ash or gangue powder is mainly used as grouting material, and compaction grouting is carried out in the main stratum under the key stratum, thus realizing the control of surface subsidence and the protection of buildings (structures). In the process of grouting filling, slurry with high water-cement ratio (1:1) is needed to ensure its injectability and certain flow radius, which leads to large water demand and limited application in water-deficient mining areas. In addition, special geological structures such as faults have potential risks of slurry flowing into the working face. On the premise of not affecting the grout injectability, how to reduce the total water consumption of grout is one of the difficult problems to be solved urgently in the overburden isolated grouting injection. The experimental study on the feasibility of ultrasonic water reduction of grouting slurry is carried out in this paper, and the influence of ultrasonic cavitation on the fluidity of slurry is studied through experiments. The results show that ultrasonic waves can effectively improve the fluidity of slurry. Under the same fluidity, the water used for slurry preparation is reduced by 20% to 26%, and when the slurry with water-cement ratio of 0.8:1 is modified, its fluidity is equivalent to that of the slurry with a water-cement ratio of 1:1 in conventional engineering applications. The action time and power of the ultrasonic waves are the key factors affecting the modification effect of the slurry, and the ultrasonic power has a more significant influence on the action effect. The proposed ultrasonic cavitation water reduction modification method can effectively reduce the water used for slurry preparation, improve the efficiency, reliability and economic benefits of grouting filling, and provide important support for the application of the grouting filling method in restricted mining areas such as water-deficient mining areas. Full article

In this study, cement, short-cut carbon fibers, and polymer water-absorbing resin were used as the main materials, with high-performance water-reducing polycarboxylic acid agent as the modified material. A new conductive cement-based grouting material was developed by incorporating functional additives. Its mix design was optimized based on initial setting time, fluidity, bleeding rate, and compressive strength. The optimal ratio of the grouting material was determined as follows: 0.4 wt% of high water-absorbent resin, 0.25 wt% of high-efficiency water reducer, 0.8 wt% of short-cut carbon fibers, and a water–cement ratio of 0.8:1. The electrical conductivity of the grouting material was studied in depth under different dosages of short-cut carbon fibers, considering factors such as curing age, temperature, and pressure conditions. The results show that with the increase in curing age, the volume resistivity of the specimen gradually increases; the resistivity of the conductive cementitious grouting material decreases with the rise in temperature, showing a negative temperature coefficient effect; additionally, the doping of an appropriate amount of short-cut carbon fibers enables the conductive cementitious grouting specimen to exhibit good pressure-sensitive properties. Field test verification indicates that the new cementitious conductive grouting material has excellent conductive properties, and the grouting quality can be effectively evaluated via high-density electrical testing. Full article

Deep multi-coal seam mining is plagued by intense mining pressure, significant impacts of multi-working face mining on system roadways, and difficult surrounding rock deformation control—these issues severely threaten the safe and normal operation of roadways, creating an urgent need for effective dynamic disaster control technologies. Taking the 131,105 working face of Liuzhuang Mine (burial depth up to 740 m) as an example, this study addresses a critical research gap; existing roof cutting pressure relief technologies mostly focus on shallow/thin-coal-seam mining and fail to tackle secondary dynamic pressure induced by repeated mining in deep multi-coal seams—where the superposition of mining stress, ground stress, and goaf stress severely threatens system roadways. To fill this gap, three novel contributions are made. (1) A hierarchical “upper break and middle cut” deep-hole blasting design is proposed, distinct from single-mode roof cutting in existing studies. It achieves directional roof failure by “upper break” (damaging overlying hard rock) and “middle cut” (creating fissures between goaf and protective coal pillars), blocking stress transmission to roadways. (2) Numerical simulations specifically for deep strata (740 m) optimize key parameters: 25 m as the optimal cutting height and 35° as the optimal cutting angle, quantifying their effects on pressure relief (a gap in existing parameter optimization for deep mining). (3) A rapid sealing scheme combining AB material grouting with high-strength detonator pins is developed, solving the problem of slow hardening and poor sealing in traditional deep-hole processes (e.g., cement-only sealing), enabling blasting within 10 min after sealing. This cut off the integrity of the roof, blocked the pressure transmission of the roof stress to the existing system roadway, and achieved a 43.7% reduction in roadway surrounding rock stress (from 32 MPa to 18 MPa) and a 46.7% reduction in maximum roadway deformation (from the pre-blasting 15 cm to 8 cm). This study provides a reference for similar deep multi-coal seam projects. Field monitoring and numerical simulation results show the following. (1) The maximum deformation of the protected East Third Concentrated main roadway is only 8 cm, fully meeting normal operation requirements. (2) The “upper break and middle cut” technology effectively reduces the mining influence range (from 156 m without roof cutting to 125 m with 25 m roof cutting) and weakens roof stress transfer to roadways. This study verifies the feasibility and effectiveness of deep hole blasting for roof cutting, pressure relief, and roadway protection in deep multi-coal seam mining. It provides direct technical references and engineering application templates for similar projects facing roadway protection and dynamic disaster control challenges, contributing to the safe and efficient mining of deep coal resources. Full article

Grout propagation is a critical aspect of fracture grouting. This study investigated grout propagation at fracture intersections under flowing conditions using a simplified two-dimensional (2D) fracture network. Transparent soil technology was employed to simulate the porous filling material within the fractures. The results showed that the penetration velocity of grout decreased significantly after passing through an intersection, and the velocity in the main fracture was consistently higher than that in the branch fractures. In the unfilled fracture network, the diffusion ratio between branch and main fractures ranged from 0.35 to 0.88, whereas after filling, it ranged from 0.71 to 0.86. For each intersection, the ratio of grout length in the downstream branch to that in the main fracture (RDM) was positively correlated with branch width. This trend was especially evident in unfilled fractures, whereas in filled fractures, the increase in RDM was much less pronounced. Regarding the upstream ratio (RUM), it was consistently lower than RDM. RUM increased with branch width in unfilled fractures but decreased in filled fractures. Additionally, higher fluid velocity amplified these anisotropic propagation behaviors. Based on the simplified filled fracture model, it was concluded that porous filling materials reduce permeability differences between fractures with different aperture widths. Furthermore, increased flow rate intensified the anisotropic diffusion of grout. This study provides valuable insight into the mechanism of anisotropic grout propagation and offers guidance for engineering grouting applications. Full article

The integration of bacterial biotechnology into construction and geotechnical practices is redefining approaches to material sustainability, infrastructure longevity, and environmental resilience. Over the past two decades, research activity in construction biotechnology has expanded rapidly, with more than 350 publications between 2000 and 2024 and a five-fold increase in annual output since 2020. Beyond bibliometric growth, technical studies have demonstrated the remarkable performance of bacterial systems: for example, microbial-induced calcium carbonate precipitation (MICP) can increase the compressive strength of treated soils by 60–70% and reduce permeability by more than 90% in field-scale trials. In concrete applications, bacterial self-healing has been shown to seal cracks up to 0.8 mm wide and improve water tightness by 70–90%. Similarly, biofilm-mediated corrosion barriers can extend the durability of reinforced steel by significantly reducing chloride ingress, while bacterial biopolymers such as xanthan gum and curdlan enhance soil cohesion and water retention in eco-grouting and erosion control. The novelty of this review lies in its interdisciplinary scope, integrating microbiological mechanisms, materials science, and engineering practice to highlight how bacterial processes can transition from laboratory models to real-world applications. By combining quantitative evidence with critical assessment of scalability, biosafety, and regulatory challenges, this paper provides a comprehensive framework that positions construction biotechnology as a transformative pathway towards low-carbon, adaptive, and resilient infrastructure systems. Full article

As a key connection technology in prefabricated buildings, offshore wind power, and bridge engineering, the performance and environmental sustainability of grouted sleeve connections are essential for the long-term development of civil infrastructure. To address the environmental burden of conventional high-strength cement-based grouts, an eco-friendly sleeve grouting material incorporating industrial solid waste was developed. In this study, silica fume (15%) and fly ash (5%) were employed as supplementary cementitious materials, while nanosilica (NS) was introduced to enhance the material properties. Mechanical testing, microstructural characterization, and half-grouted sleeve uniaxial tensile tests were conducted to systematically evaluate the effect of NS content on grout performance. Results indicate that the incorporation of NS significantly accelerates the hydration of silica fume and fly ash. At an optimal dosage of 0.4%, the 28-day compressive strength reached 105.5 MPa, representing a 37.9% increase compared with the control group without NS. In sleeve tensile tests, specimens with NS exhibited reinforcement necking failure, and the load–displacement response closely aligned with the stress–strain behavior of the reinforcement. A linear relationship was observed between sleeve wall strain and reinforcement stress, confirming the cooperative load-bearing behavior between the grout and the sleeve. These findings provide theoretical guidance and technical support for developing high-strength, low-impact grouting materials suitable for sustainable engineering applications. Full article

Polyurethane grouting materials are polymer materials formed through the reaction of polyisocyanates and polyols. They play important roles in underground engineering, tunnel construction, and mining due to their fast reaction rate, high bonding strength, and excellent impermeability. However, traditional polyurethane grouting materials have shortcomings such as high reaction heat release, high brittleness, and poor flame retardancy, which limit their applications in high-demand engineering projects. This paper systematically reviews the research progress on modified polyurethane grouting materials. Four major modification technologies are summarized: temperature reduction modification, flame retardant modification, mechanical enhancement, and environmental adaptability improvement. A multi-dimensional performance characterization system is established, covering slurry properties, solidified body performance, microstructure characteristics, thermal properties and flame retardancy, diffusion grouting performance, and environmental adaptability. The application effects of modified polyurethane grouting materials in grouting reinforcement, grouting water plugging, and grouting lifting are analyzed. Future development directions are projected. This review is particularly valuable for researchers and engineers working in tunneling, mining, geotechnical engineering, and infrastructure rehabilitation. Full article

This study presents a novel approach to determine the composition of masonry mortars and their types from cement, lime, and cement–lime using an artificial neural network (ANN). It also allows the preparation of mortar recipes for the conservation of historical masonry objects with properties similar to the original ones, but using currently available raw materials. An ANN was trained using a set of cement, lime, and cement–lime mortars with known compositions. The properties chosen for the ANN’s analysis included total porosity, specific density, insoluble residue content, silicone (SiO₂) content, calcium (CaO) content, Si/Ca ratio in grout, and compressive strength. The use of ANNs allows for the determination of mortar composition with a validation error of less than 5% and a method of classification of the type of mortar that gives correct answers in more than 93% of cases, proving the usefulness of ANNs in determining the type and composition of masonry mortars relevant for the conservation of historical masonry structures. Full article

Cracking is the most prevalent deterioration issue in historic masonry, and grouting represents one of the most effective intervention techniques. Superplasticizer-free Natural Hydraulic Lime (NHL) grout is recommended for heritage conservation due to its simple composition and compatibility with historic masonry in terms of strength, porosity, and other properties. However, grout shrinkage is frequently observed in practice, often leading to suboptimal reinforcement outcomes. This study focuses on the shrinkage characteristics of NHL grouts. Three sets of experiments were designed to investigate the influence: grout composition, expansive agents, and substrate properties. Using Taguchi’s method, an optimized combination of water, binder, and aggregate was identified. Shrinkage measurements after curing for 28 days demonstrated that calcium oxide (CaO)-based expansive agents was the best choice to compensate for NHL grout shrinkage. In addition, grouting simulation experiments evaluated suitable formulations for common masonry substrates and clarified the significant impact of substrate water absorption on the degree of shrinkage grout. For substrates with a capillary water absorption coefficient greater than 25 kg/m² h^1/2, the use of expansive agents should be strictly controlled. The findings can provide valuable insights for optimizing the grouting reinforcement of historic masonry structures and offer direct material design strategies for practical engineering applications. Full article

With rising global temperatures, roads in the permafrost regions of the Qinghai–Tibet Plateau are exhibiting issues such as subsidence, water accumulation alongside the roads and in their foundations, and ongoing permafrost degradation. Among these issues, water accumulation has emerged as a prominent challenge in road management. In this study, sodium-based-bentonite-modified cementitious waterproof grouting materials were prepared and utilized as functional barrier layers. The rheological properties, mechanical strength, flowability, and setting time of the materials were tested under different sodium bentonite dosages. The feasibility of the application of these materials was evaluated, accounting for the evolution of pressure, flow rate, and diffusion distance of permafrost subgrades over different time scales when the materials were applied as functional barrier layers. The results indicate that, when used as a functional barrier layer, the modified cement-based grouting material exhibits a fluidity that meets the upper limit of grouting requirements, with a controllable setting time. Both compressive strength and apparent viscosity rise with the addition of sodium-based bentonite (Na-bentonite). Notably, an appropriate viscosity range of 0.35–0.50 Pa·s was found to effectively resist groundwater erosion while satisfying the critical performance requirements for grouting applications, demonstrating excellent applicability. In the field grouting test, the effects of grouting pressure and flow rate over different time scales on soil cracking, spreading distance, and the crack-filling process were further analyzed. Based on these findings, a technical solution using a new type of subgrade treatment material (functional barrier layer) was proposed, providing a reference for related theoretical research and engineering practice. Full article

The increasing depth of coal mine construction has led to complex geological conditions involving high ground stress and elevated groundwater levels, presenting new challenges for water-sealing technologies in rock microfissure grouting. This study investigates ultrafine cement grouting in microfissures through systematic analysis of slurry properties and grouting simulations. Through systematic analysis of ultrafine cement grout performance across water–cement (W/C) ratios, this study establishes optimal injectable mix proportions. Through dedicated molds, sandstone-like microfissures with 0.2 mm apertures and controlled roughness (JRC = 0–2, 4–6, 10–12) were fabricated, and instrumented with fiber Bragg grating (FBG) sensors for real-time strain monitoring. Triaxial stress-permeation experiments under 6 and 7 MPa confining pressures quantify the coupled effects of fissure roughness, grouting pressure, and confining stress on volumetric flow rate and fissure deformation. Key findings include: (1) Slurry viscosity decreased monotonically with higher W/C ratios, while bleeding rate exhibited a proportional increase. At a W/C ratio = 1.6, the 2 h bleeding rate reached 7.8%, categorizing the slurry as unstable. (2) Experimental results demonstrate that increased surface roughness significantly enhances particle deposition–aggregation phenomena at grouting inlets, thereby reducing the success rate of grouting simulations. (3) The volumetric flow rate of ultrafine cement grout decreases with elevated roughness but increases proportionally with applied grouting pressure. (4) Under identical grouting pressure conditions, the relative variation in strain values among measurement points becomes more pronounced with increasing roughness of the specimen’s microfissures. This research resolves critical challenges in material selection, injectability, and seepage–deformation mechanisms for microfissure grouting, establishing that the W/C ratio governs grout performance while surface roughness dictates grouting efficacy. These findings provide theoretical guidance for water-blocking grouting engineering in microfissures. Full article

Coral sand grouting materials can effectively meet the new development requirements of remote island and reef engineering projects, demonstrating significant application value. However, its early-age shrinkage deformation may compromise structural stability. To effectively regulate this early shrinkage behavior, this study investigated the influence of varying dosages of early strength agent (ES), plastic expansive agent (PEA), and post-hardening expansive agent (HP-CSA) on the complete vertical expansion rate curve of coral sand grouting materials during 0–48 h, while comparatively examining the combined effects of composite expansive agents on early autogenous shrinkage and drying shrinkage characteristics. The results show that during 0–48 h, ES and composite expansive agents can precisely control the activation window of PEA, enabling controllable development of ultra-early vertical expansion in the grouting material, with increased HP-CSA dosage accelerating the progression of the complete vertical expansion rate curve. From 2 to 28 days, the coral sand grouting materials exhibit continuous shrinkage development. An appropriate combination of PEA and HP-CSA effectively synergizes to regulate shrinkage deformation. The drying shrinkage significantly correlates with the water loss rate. Within the scope of this study, when the dosages of ES, PEA, and HP-CSA are 1%, 0.06%, and 4%, respectively, the performance of coral sand grouting materials is relatively good. Full article

Against the backdrop of China’s “dual-carbon” initiative, this study innovatively applies a process-based life cycle assessment (PLCA) methodology, meticulously tracking energy and carbon flows across material production, transportation, and maintenance processes. By comparing six asphalt pavement maintenance technologies in Xinjiang, the research reveals that milling and resurfacing (MR) exhibits the highest energy consumption 250,809 MJ/10³ m²) and carbon emissions (15,095.67 kg CO₂/10³ m²), while preventive techniques like hot asphalt grouting reduce emissions by up to 87%. The PLCA approach uncovers a critical insight: 40–60% of total emissions originate from the raw material production phase, with cement and asphalt identified as primary contributors. This granular analysis, unique in regional road maintenance research, challenges traditional assumptions and emphasizes the necessity of upstream intervention. By contrasting reactive and preventive strategies, the study validates that early-stage maintenance aligns seamlessly with circular economy principles. Tailored to a local arid climate and vast transportation network, the study concludes that prioritizing preventive maintenance, adopting low-carbon materials, and optimizing logistics can significantly decarbonize road infrastructure. These region-specific strategies, underpinned by the novel application of PLCA, not only provide actionable guidance for local policymakers but also offer a replicable framework for sustainable road development worldwide, bridging the gap between scientific research and practical decarbonization efforts. Full article