In response to the severe dust pollution, high operational cost, and short-lived effectiveness associated with conventional water-spraying dust suppression in large open-pit coal mines in grassland regions, this study proposes a source-control strategy grounded in solid waste reutilization. Drill cuttings of mudstone obtained from a representative overburden bench in the study area were utilized as the primary precursor, and a modified mudstone-fly ash geopolymer stemming material was developed via an alkali-activated rapid-setting process. The proposed material enables synergistic optimization of explosive energy confinement and dust suppression at the source during blasting operations.The dust-suppression mechanism of the proposed material was systematically investigated through mechanical performance testing, SEM, XRD, EDS, and smoothed particle hydrodynamics (SPH) simulations.Results show that optimal performance is obtained with a 30% accelerator concentration, a water-glass modulus of 1.50mol/L at 40g/L dosage, and a mixing time of 5min, yielding good flowability and setting times within 30min. Dynamic tests indicate superior toughness, with initiation and propagation fracture toughness of 0.80-2.41MPa m1/2 and 0.61-2.56MPa m1/2, respectively, and a peak stress approximately 7.5% higher than that of in-situ mudstone. Microstructural analyses reveal that synergistic formation of C-S-H and C-A-S-H gels produces a dense and stable matrix.SPH simulations identify an optimal stemming length of 2.5m for uniform energy distribution. Field trials demonstrate reductions of 40.0% in peak dust concentration and 0.346cm/s in maximum vibration velocity, alongside improved fragmentation and suppressed blowout holes. The results demonstrate that the proposed geopolymer stemming material enables a technological transition from conventional post-blast water spraying to in-blast active solidification control. By enhancing explosive energy utilization while achieving source-level dust suppression, the material provides a green, cost-effective, and durable solution for blasting optimization in grassland open-pit coal mines.

Fracture Propagation of Radial Borehole Fracturing in Conglomerate Reservoirs: A Laboratory Study

A study on the fracture mechanical properties and propagation mechanism of coarse aggregate-engineered cementitious composites under preloading

Geomechanical Multifactor Coupling and Hydraulic Fracture Propagation Evaluation Model for Fracability Based on a Multiplicative Synthesis Method

A novel fluid-solid coupling method for simulating fracture propagation induced by detonation gas

Hydraulic fracture propagation characteristics in coal mines hard roof rocks with PAM fracturing fluid

Research on asymmetric deformation of roadway roof based on non-closed fracture propagation mechanism induced by principal stress rotation

Competitive fracture propagation across different regimes during multi-stage hydraulic fracturing

Impact of cluster spacing on uneven fracture propagation in multi-cluster perforation fracturing under stress shadow effects

During the extraction of shale oil from the Longmaxi Formation in the Sichuan Basin, it is found that the core samples contain natural fractures cemented by various minerals. However, the core extraction process is complex and expensive. In order to further investigate how cracks propagate and initiate in samples containing cementing layers under compression conditions, this study developed an experimental method involving plug cutting and mineral cementation reconstruction for the preparation of representative semi-artificial core samples. Through comprehensive analysis using computed tomography (CT), stereomicroscopy, and mechanical testing, we have demonstrated a high degree of consistency between artificial cemented cracks and natural cemented cracks. Through triaxial compression and Brazilian splitting experiments on artificially cemented samples, we found that low and high confining pressures significantly affect crack morphology. By using Abaqus finite element simulation to add crack propagation modes during the compression process of cement layers, we showed that different mineral cements (quartz, clay, and calcite) have secondary effects on crack morphology on the basis of confining pressure.

Abstract Regarding the unclear mechanism of fracture propagation in bedded rocks during supercritical CO 2 (SC-CO 2 ) fracturing, this study proposed a method for fabricating artificial bedded rock specimens using modeling materials. Based on these specimens, true triaxial SC-CO 2 fracturing experiments were conducted to systematically investigate the effects of bedding structure and rock matrix brittleness on fracture propagation behavior and initiation pressure. A spatial development index was introduced to quantitatively characterize the extent and complexity of fracture growth in 3D space. The findings indicate that among bedding angle, bedding spacing, and rock matrix brittleness, bedding angle has the greatest influence on fracture initiation pressure. Compared with matrix brittleness, the bedding structure exerts a more significant impact on fracture spatial configuration. To overcome the limitations of conventional brittleness evaluation methods when applied to bedded rocks, two theoretical models were developed to predict Poisson’s ratio and elastic modulus across various bedding angles. Based on these models, a novel brittleness prediction approach—integrating mineral composition, mechanical parameters, and bedding angle—was proposed, enabling a more accurate characterization of the overall brittleness of bedded rocks. Notably, while previous studies have indicated an inverse relationship between rock brittleness and initiation pressure, this study demonstrates that this inverse relationship holds only under constant bedding angles. When bedding angles vary, the relationship shifts to a positive one. This study not only provides an effective method for scientific evaluating brittleness in bedded rock but also offers theoretical support for designing and optimizing SC-CO 2 fracturing strategies in bedded reservoirs.

Basalt fiber-reinforced concrete is increasingly being used in shotcrete support systems for rock mass excavation engineering due to its superior mechanical properties and durability. Rapid freeze-thaw cycling tests were performed to simulate freeze-thaw conditions in order to meticulously investigate the dynamic and static fracture behaviors of basalt fiber-reinforced concrete in freeze-thaw environments. Then, utilizing a Split Hopkinson Pressure Bar (SHPB) system and rock testing equipment, dynamic and static fracture tests were performed on developed Mode I, mixed-mode I/II, and Mode II platform Brazilian disk specimens. Under freeze-thaw conditions, the dynamic and static fracture propagation velocities of specimens with diverse crack propagation modes were determined. Based on this, LS-DYNA numerical simulations were used to perform inverse evaluations of crack propagation processes in specimens with varied fracture modes and Mode I fracture specimens with variable basalt fiber contents. We were able to calculate the effective stress field distributions during crack propagation with dynamic loading. The data indicate that different fracture modes present significantly distinct crack propagation issues. Pure Mode I fracture specimens exhibit the most straightforward crack propagation, with a maximum effective stress of roughly 25 MPa after crack penetration. With a maximum effective stress of around 31 MPa following crack penetration, the mixed-mode I/II fracture specimens exhibit considerable propagation difficulties. Mode II fracture specimens are the hardest to propagate after crack penetration because of their maximum effective stress of 64 MPa. Additionally, the optimal basalt fiber content was determined to be in the range of 0.35% to 0.45%, at which the concrete exhibited the best fracture toughness and freeze-thaw resistance. Furthermore, the evolution characteristics of the displacement of the crack tip opening under different fracture modes are revealed. A theoretical basis for stability analysis and design of excavation engineering structures under dynamic stress and associated freeze-thaw conditions is provided by the study's findings.

The tight sandstone reservoirs of the Tarim Basin in China are characterized by vertically stacked multi-sweet spots. However, the strong vertical heterogeneity and discontinuity limit the effectiveness of hydraulic fracturing for multilayered co-production. To investigate the mechanisms governing the vertical cross-layer propagation of hydraulic fractures in the multilayered sandstone reservoir, outcrop rocks of fine sandstone and siltstone from the area were collected. Subsequently, these rocks were cemented to fabricate multilayered experimental samples with lithological transition zones. Hydraulic fracturing experiments were performed to systematically study fracture propagation behavior, with particular focus on the influence of interlayered lithology, vertical stress differences, fracturing fluid injection rate, and fluid viscosity on vertical fracture growth. Experimental results demonstrate that hydraulic fracturing in multilayered sandstone can form both passivated and cross-layer fracture networks while also activating lateral propagation along lithological transition zones. When hydraulic fractures extend from high-brittleness layers to low-brittleness layers, their vertical propagation is limited, promoting shear activation along lithological transition interfaces. As the vertical stress difference increases, the vertical propagation range of hydraulic fractures expands progressively, with fracture morphology evolving from a passivated type to a single-wing cross-layer pattern and further developing into a bi-wing cross-layer geometry. Increasing the injection rate and viscosity of the fracturing fluid enhances cross-layer fracture propagation while suppressing the activation of lithological transition zones. The insights derived from this study can provide a theoretical foundation and engineering guidance for the design and implementation of hydraulic fracturing in multilayered tight sandstone reservoirs in the Tarim Basin.

ABSTRACT In this paper, we propose a novel multiphase approach for identifying input parameters in dynamic fracture propagation. Often, such parameters are partially known and uncertain with incomplete input data, resulting in challenges in predicting a reliable dynamic failure response. To address this, we employ a stochastic Bayesian inverse method to estimate input parameters in three distinct phases of a fracture model. As a case study, we analyze a virtual version of Kalthoff's dynamic fracture propagation test using a finite element model enhanced with embedded strong discontinuities, where cracks propagate in a mixed‐mode manner, to demonstrate the effectiveness and robustness of the proposed method. The approach successfully identifies six material parameters, including the bulk modulus, shear modulus, tensile strength, shear strength, and the modes I and II fracture energies. Through different time intervals and measurements in each phase, our results show that the computed posterior mean values are closely aligned with the true parameters of the material, validating the reliability and accuracy of the method.

Characterization of acoustic emission parameters and identification of staged fracture propagation in solidified body-coal combination based on experimental and machine learning approaches.

Economic gas recovery from shale reservoirs is inherently difficult because of the extremely low permeability of these formations. To overcome this challenge, horizontal wells are drilled and subjected to multi-stage hydraulic fracturing treatments, which generate high-conductivity flow pathways. The adoption of these technologies has significantly boosted the economic recovery of gas from shale formations, particularly the Marcellus Shale, which stands as the most productive shale gas play in the United States. The effectiveness of a fracturing treatment in enabling economic gas production from shale reservoirs is governed by the characteristics of the fractures it creates. The propagation of initial fracture, during multi-stage hydraulic fracturing, modifies the initial stress conditions in the surrounding area, commonly referred to as a “stress shadow.” The stress shadow restricts the initiation and subsequent propagation of later fracture stages, leading to the development of less favorable fracture properties. As a result, the uneven contribution of individual fracture stages to gas flow ultimately diminishes overall gas recovery from the horizontal well. For efficient gas drainage from the shale, the fracture stages are often closely spaced. When fracture stages are placed in close proximity, the stress shadow effect can be intensified. Thus, accounting for the stress shadow is essential in the design of hydraulic fracture treatments. This study investigates how fracture spacing, injected fluid volume, and fluid type influence the magnitude of the stress shadow effect, its impact on fracture properties, and the resulting gas recovery from the Marcellus Shale. The goal is to facilitate the optimization of the hydraulic fracture design to mitigate the stress shadow impact and enhance gas production. Data from several Marcellus Shale horizontal wells, along with published findings, were compiled and analyzed to determine the petrophysical and geomechanical characteristics of the formation. These results were then used to construct a reservoir model representative of a Marcellus Shale horizontal well. Fracture properties, altered by the stress shadow, were assessed through hydraulic fracturing simulations and incorporated into the model. Ultimately, the reservoir model was employed to predict the production performance. The results of the investigation confirmed that close stage spacing intensifies the impact of the stress shadow. The stress shadow was found to impair fracture conductivity which negatively impacted gas recovery. The negative impact of the stress shadow on gas recovery was observed to gradually diminish as the production rate declined over time. The volume and type of the fluid injected during fracturing treatment can amplify the stress shadow’s impact.

To address the unclear mechanisms of hydraulic fracture propagation in shale reservoirs with well-developed bedding and complex thin interbedded layers, this study first employed three-point bending tests combined with Digital Image Correlation technology to reveal the fundamental laws of fracture propagation. Building on this, a numerical model for vertical fracture propagation was established, taking into account bedding planes with different orientations. The model utilizes globally embedded cohesive zone elements to simulate the initiation and propagation of hydraulic fractures in the vertical direction. Simulations were conducted to investigate fracture vertical propagation behavior under bedding-developed conditions, and a systematic analysis was performed on the controlling effects of key geological parameters on fracture morphology. The results clarify the influence mechanisms of reservoir and interlayer physical properties on fracture pathways, providing direct guidance for the design and optimization of hydraulic fracturing in similar strongly heterogeneous shale reservoirs.

The development of low-permeability reservoirs faces significant challenges, particularly regarding low recovery rates. Conventional water injection is often limited by poor injectivity and low waterflood efficiency. As a key technology to enhance development effectiveness, enhanced water injection requires a systematic investigation into its intrinsic mechanism for improving recovery. This study focuses on a typical low-permeability reservoir. Through laboratory experiments on rock fracturing and spontaneous imbibition, the mechanism by which enhanced water injection increases recovery rates is elucidated. COMSOL Multiphysics is employed to simulate the enhanced water injection process and examine the multi-field coupling patterns during injection. The results indicate that (1) low-permeability rocks in the study area exhibit strong oil–water exchange capabilities driven by capillary forces, with average imbibition capacity ranging from 0.6 to 0.7 g/cm3 and oil displacement efficiency between 20% and 30%; (2) fracturing experiments demonstrate that the injection of low-viscosity fluids at low flow rates (15 mL/min) can induce complex fracture propagation, thereby expanding flow pathways; and (3) the evolution of fluid–solid coupling is jointly governed by injection pressure and damage effects. Specifically, coupling intensity and fracture propagation potential increase with pressure, with optimal injection pressure ranging from 20 to 25 MPa. Rock damage exacerbates the nonlinear response of this coupling. This study combines experimental validation with numerical simulation to provide theoretical support for field practice.

The subsurface mechanical damage (SSD) depth after grinding fused silica glass with a comprehensive set of sub-aperture fixed abrasive grinding tools [cup, wheel, belt, pad, and rotary face mill (with and without ultrasonics)] and process parameters has been statistically measured using the taper wedge technique and evaluated. Consistent with a previously reported grinding model [ J. Non-Cryst. Solids 352 , 5601 –5617 ( 2006 ) 10.1016/j.jnoncrysol.2006.09.012 , Materials Science and Technology of Optical Fabrication (Wiley & Sons, 2018 ) ], based on the sliding indentation fracture by sliding particles or asperities where the normal load per particle determines the depth of the fracture (and ultimately the overall SSD depth), the dominant factor controlling SSD depth was found to be the abrasive size regardless of the tool type and process conditions. Compared to full aperture grinding methods, the overall SSD depth was higher using the sub-aperture tools, likely due to the higher effective pressure and higher load per particle distribution. In addition to abrasive size, a significant reduction in SSD depth was achieved by: (1) reducing the load distribution on the abrasive particles via increase in contact area and/or decrease in mechanical loading; (2) using a more compliant host tool medium; and (3) in what we believe is a more novel way, using ultrasonics. Combining low abrasive size, larger contact area, and a compliant host, the 6 µm diamond in a resin matrix (Trizact) on a foam pad led to very low SSD depth (∼4.6µm), relatively fast grinding rate (186mm 3 /h), and little or no figure degradation. This grinding tool/process is an attractive choice for final grind, resulting in significantly reduced polish out (i.e., “grey out”) times. With the rotary face mill tool, the use of ultrasonics consistently led to a SSD depth reduction (ranging from 17%–34%). A new fracture mechanics-based model, to the best of our knowledge, where the relevant normal load is parallel to the feed direction, has been developed to explain how ultrasonics leads to lower SSD depth. The key factors, supported by finite element stress analysis and load measurements, are (1) the initiation of fractures at higher z heights during the tool’s ultrasonic vertical oscillations, thus propagating less deep into workpiece; (2) reduction in load (and therefore reduction in fracture propagation distance) due to smaller tool-workpiece feed direction contact area (again caused by higher z heights relative to depth of cut); (3) upward movement of the tool during oscillation leads to fracturing toward the surface instead into the depth; and finally (4) at tool’s lowest point of oscillation cycle, there may not be enough time for the fracture to propagate to its full length.

ABSTRACT To solve limestone floor water inrush and reduce accidents, this paper studies Fengxianglin Coal Mine. It uses field investigation, mechanical experiments, similar simulation and engineering numerical simulation to explore limestone floor damage, Maokou Formation fracture development, and the influence of advancing distance, coal seam burial depth, aquitard thickness and floor water pressure on floor water inrush during coal—seam mining above confined water. Results show that stress—strain curves of limestone with different water content have four stages: initial stress growth, crack compaction, stress increase and stress drop. Water dissolution softens limestone, enhances nonlinear deformation and changes failure mode from local brittle to overall plastic. The coupling of pore water pressure and mining stress reduces floor strata strength and raises water inrush risk. Digital image correlation (DIC) technology monitoring shows that in the process of working face advancing. The maximum principal strain concentration range and degree of strata gradually expand. The strain distribution is ‘W’ shape, and the displacement curve is irregular ‘M’ shape. Water inrush occurs when the floor damage zone connects with the aquifer water channel. Numerical simulation reveals that increasing advancing distance raises floor fractures and pore pressure. Pore pressure distribution changes from inverted ‘circular arch’ to inverted ‘concave’ with increasing coal seam burial depth. Increasing aquitard thickness reduces pore pressure and inhibits fracture propagation. Increasing floor water pressure accelerates crack propagation and heightens water inrush risk.