Search Results (662)

The article is devoted to the issues of designing the exploitation of a seam deposit in the boundary areas of underground mines in terms of minimizing the risk of dynamic phenomena. Its main goal was to attempt to demonstrate the relationship between the method of extracting resources trapped in the boundary pillar and the magnitude of the induced seismicity of the rock mass accompanying this process. The substantive considerations concerned the single-wall model and were divided into two main parts—theoretical and verification. As part of the theoretical piece, based on model studies, a geomechanical assessment of the impact of the working face advance on changes in the stress–strain behaviour occurring in the burst-prone layer in terms of the possible loss of continuity of its original structure was carried out. The starting point for the key analyses were the results of numerical simulations based on the algorithms of S. Knothe and W. Budryk’s theories in combination with classical solutions of the mechanics of deformable bodies. Two variants of mining operations in a two-sided environment of goaf were considered, differing in the direction of progress, the degree of constraint of the start and end of the face advance, and mining circumstances in the vicinity of both sides of the advancing face. As part of the verification piece, the results of model analyses were related to an example polygon of a crossing longwall in one of the functioning, rockburst USCB hard coal mines. The scope of the research included a comparison of the experimentally indicated zones of occurrence of tremor-favourable effort processes in the roof of the seam with the actual location of the seismic phenomena foci recorded during the ongoing exploitation. The considerations included in the work formed the basis for formulating conclusions of a cognitive and applicable nature. Full article

Deep soft rock roadways at about 1 km depth experience significant deformation due to concentrated stress ahead of the working face and dynamic loads from the hard roof layer. We propose an integrated control method that couples directional roof cutting, which interrupts stress transfer with constant resistance, and large deformation cable reinforcement to accommodate residual movement. The calibrated FLAC3D model indicates a lower front of face stress and a diminished cyclic build up of elastic strain energy in the roof, which reduces roadway convergence. Field data from Face 13403 corroborate the method’s effectiveness: the average hydraulic support load on the roof cutting side was 20.3 MPa, which is 30.1% lower than on the non-cutting side; deformation stabilized about 320 m behind the face; the final roof to floor and rib to rib closures were 1.10 m and 1.47 m; and the entry remained fit for the next panel. These results indicate that coupling roof cutting with constant resistance cable reinforcement reduces mining-induced loads while increasing deformation tolerance, providing a practical solution for stabilizing kilometer-deep soft rock roadways. Full article

This study presents a comprehensive review of the CLH index, a predictive tool developed to estimate the wear of tunnel boring machine (TBM) disc cutters operating in hard rock conditions. The CLH index provides a simplified, time-efficient, and cost-effective alternative to conventional wear prediction methods by employing a statistically derived empirical formula. The methodology is based on the identification and quantitative assessment of key rock properties that influence cutter wear. A detailed statistical analysis was conducted to validate the index, quantify potential errors, and determine confidence levels. As part of this review, updated reference tables are proposed to facilitate cutter wear estimation without the need for preliminary laboratory testing. These tables are derived from empirical data obtained at the Rock Mechanics Laboratory of the Higher Technical School of Mining and Energy Engineers (ETSIME-UPM), using operational records from TBM excavation in multiple Spanish high-speed railway tunnels, with a total length exceeding 120 km. The results confirm the reliability and practical applicability of the CLH index as a decision-support tool in TBM performance forecasting and maintenance planning. Full article

Multi-slice mining of the 70 m ultra-thick coal seam in East Junggar coalfield, China is marked by large-scale mining space expansion and frequent stress disturbances. To address those, this study uses theoretical analysis, physical simulation, and numerical simulation to explore the evolution of an overburden bearing structure and the control of strata behavior in multi-slice mining. The results (1) clarify the overburden fracture-hinging characteristics: fractured blocks in lower hard strata form beam-type hinges (early stage), the lower hinged structure weakens and the beam-type hinge structure moves upward in steps (middle stage), the continuous increase in the mined-out space leads to the transverse O-X fracture of far-stope rock strata, and broken rock blocks are extruded into shells (late stage); this study also proposes an identification method for the morphology of roof bearing structures (including beam structure, higher beam structure, and arch structure); (2) define the support-controlled strata range and load calculation method at different stages, and show that the support load “increases slowly under the near-stope roof bearing structure and tends to stabilize under the far-stope roof bearing structure” as the roof bearing structure moves upward; and (3) guided by the aims of avoiding cantilever beams and ensuring near-stope roof stability, lead us to propose the following measures: pre-splitting main roof (early stage); short working faces with reduced layered thickness and rapid advance (late stage); and goaf/separation grouting (whole process). The maximum support load drops from 20,017.5 kN to 16,192.5 kN, enabling lightweight support selection. This study provides theoretical guidance for support selection and roof control in the multi-slice mining of ultra-thick coal seams. Full article

Rockburst is a dynamic disaster that frequently occurs in hard and brittle rock tunnels under high in situ stress conditions. It is influenced by multiple factors, including lithological condition, in situ stress condition, and surrounding rock mass structural condition. Rockbursts are highly destructive and difficult to predict accurately. At present, many methods have been proposed for predicting rockburst proneness. However, the above methods suffer from a lack of diversity, limited applicability, and low predictive accuracy. Therefore, based on the Analytical Hierarchy Process (AHP) method and fuzzy mathematics theory, the eight evaluation indexes (strength brittleness index, stress coefficient, elastic energy index, surrounding grade, etc.) were selected to establish the new AHP fuzzy comprehensive evaluation model. Based on the field case studies, the feasibility and accuracy of the model were validated. The results indicate that the proposed multi-index prediction model demonstrates strong feasibility and high predictive accuracy, and the model has promising application prospects. Meanwhile, the 13 recognized evaluation indexes were summarized, and an approach for accurate rockburst prediction was proposed. The predicting model and predicting approach proposed in this paper are of great significance for improving the accuracy of rockburst prediction. Full article

Hydraulic fracturing is a technique employed to weaken rock formations during hard rock excavation. This study aims to investigate the impact of hydraulic fracturing on crack propagation in rock walls and its subsequent effect on the load borne by roadheaders during the cutting of pre-cracked rock. A three-dimensional model for the crack growth process in rock walls under hydraulic fracturing is developed using the CFD-DEM (Computational Fluid Dynamics–Discrete Element Method) two-way fluid–structure coupling approach. The results indicate that crack propagation under hydraulic fracturing occurs in four distinct phases: the initiation of the main crack, the further development of the main crack, the fine cracking phase, and the retardation of the main crack with the subsequent expansion of secondary cracks. The study analyzes the influence of pore size and water injection pressure on crack growth. It is observed that an increase in pore size and injection pressure within a certain range results in a nonlinear increase in crack propagation. Specifically, when the hydraulic fracturing aperture expands from 85 mm to 100 mm, the number of fracture bonds increases by 56.2%. Similarly, as water injection pressure rises from 25 MPa to 40 MPa, the number of broken bonds increases by 153.9%. The force exerted on rock with pre-existing cracks is found to be 9.05% lower compared to unfractured rock, with the average forces in the Z and Y directions reduced by 11.46% and 7.2%, respectively. However, the average force in the X direction increases by 5.49%. These findings provide a valuable reference for optimizing hydraulic fracturing procedures in hard rock excavation. Full article

The increasing accumulation of mineral wool waste, especially from construction and demolition sources, presents a major environmental burden. This study investigates a scalable grinding enhancement strategy using bauxite and glass cullet additives to improve the comminution of glass wool, rock wool, and mixed mineral wool waste. Mechanical grinding assisted with the use of 10 wt% and 20 wt% of hard mineral additives reduced milling time by up to 50% compared to unmodified samples, with bauxite consistently outperforming glass cullet. Laser diffraction confirmed a marked reduction in particle size, reaching sub-50 µm targets essential for alkali activation, while SEM analysis revealed smoother, fractured surfaces conducive to improved geopolymer reactivity. Energy consumption estimates suggest substantial efficiency gains; however, upstream impacts such as additive production and transport warrant further evaluation. Compared to conventional thermal and chemical pretreatments, this abrasive-assisted approach demonstrates a lower-energy pathway for producing geopolymer-compatible powders. The findings also offer guidance for developing standardized protocols and open avenues for testing these powders in future binder formulations. Full article

The extraction of geothermal energy is of great significance for sustainable energy development. The destruction of hard rock masses during geothermal well exploitation generates seismic waves that can compromise wellbore stability and operational sustainability. Seismic waves are known to be affected by rock structures like cracks and interfaces. However, a quantitative understanding of these effects on wave parameters is still lacking. This study addresses this gap by experimentally investigating the effect of crack geometry (angle and width) and rock interfaces on seismic wave propagation. Using a synchronous system for rock loading and seismic wave acquisition, we analyzed wave propagation through carbonate rock samples with pre-defined cracks and interfaces under unconfined, dry laboratory conditions. Key wave parameters (amplitude, frequency, and energy) were extracted using the fast Fourier transform (FFT) and the Hilbert–Huang transform (HHT). Our primary findings show the following: (1) Increasing the crack angle from 35° to 75° and the width from 1 mm to 3 mm leads to significant attenuation, reducing peak amplitude by up to 94.0% and energy by over 99.8%. (2) A tightly pressed rock interface also causes severe attenuation (94.2% in amplitude and 99.9% in energy) but can increase the main frequency by up to 8.5%, a phenomenon attributed to a “boundary effect”. (3) Seismic wave parameters exhibit significant spatial variations depending on the propagation path relative to the source and rock structures. This study provides a fundamental, quantitative baseline for how rock structures govern seismic wave attenuation and parameter shifts, which is crucial to improving microseismic monitoring and wellbore integrity assessment in geothermal engineering. Full article

Nano- and micro-indentation have become essential tools for quantifying the micromechanical behavior of rocks beyond traditional macroscopic tests. This review summarizes the historical evolution, experimental methodologies, and interpretation models (e.g., Oliver–Pharr, Doerner–Nix, energy-based methods, Hertz/ECM/Lawn), with a particular focus on rock-specific challenges such as heterogeneity, anisotropy, and surface roughness. A structured literature survey (1980–August 2025) covers representative studies on shale, limestone, marble, sandstone, claystone, and granite. The transition from classical hardness measurements to advanced instrumented indentation has enabled more reliable determination of localized properties, including hardness, elastic modulus, fracture toughness, and creep. Special attention is given to the applicability and limitations of different interpretation models when applied to heterogeneous and anisotropic rocks. Current challenges include high sensitivity to surface conditions and difficulties in capturing the full complexity of natural rock behavior. Looking forward, promising directions involve intelligent systems that integrate AI-driven data analytics, robotic automation, and multiscale modeling (from molecular dynamics to continuum FEM) to enable predictive material design. This review aims to provide geoscientists and engineers with a comprehensive foundation for the effective application and further development of indentation-based testing in rock mechanics and geotechnical engineering. Full article

In the presented work, a natural mineral—rock crystal—was used as a filler to obtain new silicone adhesive tapes. It was expected that, properly crushed, this hard mineral, consisting almost entirely of silica (silicon dioxide), should enhance the thermal resistance and cohesion of the self-adhesive composition with no/or low reduction in the rest of performance properties of the products. For this purpose, tests were conducted on the functional properties of new self-adhesive tapes, such as adhesion, cohesion, and tack. The obtained results confirmed the scientific assumptions and the thermal resistance of adhesive layers reached over 225 °C. The material itself turned out to not agglomerate in the adhesive composition and to be compatible with it. The new self-adhesive materials have application potential and can be used as materials for special applications in the field of heating, e.g., in connecting pipes, where thermal resistance and thermal expansion are of immense importance. Full article

In order to study the damage evolution and fracture characteristics of rock with different composite modes in three layers under dynamic loading, rock specimens with different composite modes were made by using three materials: sandstone, marble and granite. The dynamic fracture impact test was carried out by using the Hopkinson pressure bar impact loading system, the voltage signal on the Hopkinson pressure bar was calculated and processed, and the crack propagation mode of the specimen was captured by using a high-speed camera, and the stress wave characteristics, stress time–history relationship and energy change characteristics of rocks with different composite modes were studied. At the same time, combined with Distinct Lattice Spring Model numerical simulation, the fracture process of the specimen was inverted, and the changes in stress intensity factor, stress change and load–displacement change in monitoring point were analyzed to compare the dynamic fracture behavior differences between different composite rocks. The results show that the dynamic fracture process captured by the high-speed camera has a good fit with the crack propagation process simulated by numerical simulation. When marble is used as the upper material, the energy transmittance is larger, and the transmission energy ratio between sandstone and granite is basically the same due to the large difference in hardness. When the comprehensive hardness of the specimen is the same, the smaller the hardness of the material at the cracking position, the faster the cracking will be, and the smaller the hardness of the second layer of the specimen at the cracking position, the faster the cracking speed of the specimen. In terms of dynamic fracture toughness, for specimens with little difference in hardness, when the impact end material is sandstone, the dynamic fracture extreme value of the specimen is lower, and when the sandstone material is used as the impact end material, it is more likely to crack. When the first layer of material is the same, the dynamic fracture toughness of the specimen with less hardness of the second layer of material is smaller, and the easier the crack development is. Full article

The ridged cutter, a highly representative non-planar PDC cutter known for its strong impact resistance and wear durability, has demonstrated significant effectiveness in enhancing the rate of penetration (ROP) in hard, highly abrasive, and interbedded soft–hard formations. Understanding the crack evolution is fundamental to revealing the rock-breaking mechanism of ridged PDC cutters. To date, studies on rock breaking with ridged cutters have largely focused on macroscopic experimental observations, lacking an in-depth understanding of the crack evolution characteristics during the rock fragmentation process. This study employs the Finite–Discrete Element Method (FDEM) to establish a three-dimensional numerical model for simulating the interaction between the ridged cutter and the rock. By analyzing crack propagation paths, stress distribution, and the stiffness degradation factor (SDEG), the initiation, propagation patterns, and sequence of cracks around the cutter are investigated. The results indicate the following outcomes: (1) The ridged cutter breaks rock mainly by tensioning and shearing, while the conventional planar cutter breaks the rock by shearing. (2) The rock-breaking process proceeds in three stages: compaction, micro-failure, and volumetric fragmentation. (3) Crack evolution around the cutter follows the rule of “tension-initiated and shear-propagation”; that is, tensile damage first generates at the front of the crack due to tensile stress concentration, whereas shear damage subsequently occurs at the rear under high shear stress. Finally, mixed tensile–shear macro-cracks are generated. (4) The spatial distribution of cracks exhibits strong regional heterogeneity. The zone ahead of the cutter contains mixed tensile–shear cracks, forming upward-concave cracks, horizontal cracks, and oblique cracks at 45°. The sub-cutter zone is dominated by tensile cracks; the zone on the flank side of the cutter consists of a radial stress field, accompanied by oblique 45° cracks. The synergistic evolution mechanism and distribution law of tensile–shear cracks revealed in this study elucidate the rock-breaking advantages of ridged cutters from a micro-crack perspective and provide a theoretical basis for optimizing non-planar cutter structures to achieve more efficient volumetric fracture. Full article

This study evaluates adhesive bolts (chemical anchors) bonded with epoxy and vinyl ester resins for surface and tunnel excavations in tropical mining environments under static and dynamic loading. Over 300 pull-out tests in concrete and hard rock examined the effects of bolt length, curing time, and substrate condition on load capacity, failure mode, and bond–slip response. Epoxy anchors exhibited higher bond strength, including under early-age and thermally active conditions, while vinyl ester showed improved ductility and post-peak behaviour in fractured rock. Numerical modelling with Rocscience RS2 (Phase 2) and Unwedge simulated excavation responses for bolt lengths of 190–250 mm and spacings of 0.5–2.0 m. Tensile failure dominated at wider spacings, whereas closely spaced anchors enhanced confinement and redistributed stresses. The combined experimental–numerical evidence quantifies chemical-anchor performance in complex subsurface settings and supports their use for early-age support and long-term stability. Findings motivate integration of resin-grouted bolts into modern support designs, particularly in seismically sensitive or hydrothermally variable mines. Full article

Shale oil and gas reservoirs are characterized by low porosity and low permeability. The development of ultra-long horizontal wells can significantly increase reservoir contact area and enhance single-well production. Shale formations exhibit distinct bedding structures, high formation pressure, high rock hardness, and strong anisotropy. These characteristics result in poor drillability, slow drilling rates, and high costs when drilling horizontally, severely restricting efficient development. Therefore, accurately predicting the drillability of shale gas wells has become a major challenge. Currently, most scholars rely on a single parameter to predict drillability, which overlooks the coupled effects of multiple factors and reduces prediction accuracy. To address this issue, this study employs drillability experiments, mineral composition analysis, positional analysis, and acoustic transit-time tests to evaluate the effects of mineral composition, acoustic transit time, bottom-hole confining pressure, and formation drilling angle on the drillability of horizontal well reservoirs, innovatively integrating multiple parameters to construct a nonlinear model and introducing three intelligent optimization algorithms (PSO, AOA-GA, and EBPSO) for the first time to improve prediction accuracy, thus breaking through the limitations of traditional single-parameter prediction. Based on these findings, a nonlinear regression prediction model integrating multiple parameters is developed and validated using field data. To further enhance prediction accuracy, the model is optimized using three intelligent optimization algorithms: PSO, AOA-GA, and EBPSO. The results indicate that the EBPSO algorithm performs the best, followed by AOA-GA, while the PSO algorithm shows the lowest performance. Furthermore, the model is applied to predict the drillability of Well D4, and the results exhibit a high degree of agreement with actual measurements, confirming the model’s effectiveness. The findings support optimization of drilling parameters and bit selection in shale oil and gas reservoirs, thereby improving drilling efficiency and mechanical penetration rates. Full article

Under the complex geological structural stress of the Western Himalayan syntaxis, the widespread distribution of hard and brittle rocks (such as sandstone and limestone) makes them prone to the formation of conjugate joints, also known as X-joints. These joints create weak structural planes in the slope rock mass, and when combined with weak interlayers within the slope, they result in a complex dynamic response and hazard situation in this region, which is further exacerbated by frequent seismic activity. This poses a serious threat to the planning, construction, and safe operation of the Belt and Road Initiative. To study the slope vibration response and instability mechanisms under these conditions, we conducted a shaking table test using the Iymek avalanche as a case study and performed Hilbert–Huang Transform (HHT) analysis. We also compared the results of the shaking table test on slope models without X-joints but containing weak interlayers. The findings show that the presence of X-joints leads to an earlier onset of plastic failure in the slope. During the failure development, X-joints cause stress concentration and the diversification of stress redistribution paths, delaying energy release. Ultimately, the avalanche failure mode in the X-joint slopes is more dispersed compared to the landslide failure mode in the model without X-joints. At the toe of the slope beneath the weak interlayer, low-frequency seismic waves can cause a significant amplification of acceleration, and the weak interlayer is often the shear outlets of the slope. These findings provide new insights into the seismic failure evolution of jointed slopes with weak interlayers and offer practical references for seismic hazard mitigation in mountainous infrastructure. Full article