Complex Rock Mechanics Problems and Solutions, 2nd Edition

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.9	6.1	2011	15 Days	CHF 2400
Energies energies	3.9	8.3	2008	16.7 Days	CHF 2600
Geosciences geosciences	2.3	4.4	2011	22.7 Days	CHF 1800
Minerals minerals	2.7	4.9	2011	17 Days	CHF 2400
Processes processes	3.4	5.7	2013	14.7 Days	CHF 2400

22 pages, 1968 KB

Open AccessArticle

Experimental Study on the Dynamics of the “Fracture–Migration” Effect in Overburden Under Dynamic Disturbance

by Haidong Xu, Chenghong Wu, Xingping Lai, Jiantao Cao, Zhiwei Zheng and Chunyu Ji

Appl. Sci. 2026, 16(13), 6532; https://doi.org/10.3390/app16136532 - 30 Jun 2026

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To investigate overburden movement and three-zone development under far-field strong dynamic disturbance induced by instability of typical thick and hard overburden in western mining areas, a large-scale two-dimensional physical similarity simulation was conducted using the 11N0201 working face of Maiduoshan Coal Mine as [...] Read more.

To investigate overburden movement and three-zone development under far-field strong dynamic disturbance induced by instability of typical thick and hard overburden in western mining areas, a large-scale two-dimensional physical similarity simulation was conducted using the 11N0201 working face of Maiduoshan Coal Mine as the engineering background. Four test scenarios were designed: a baseline condition, dynamic loading, pressure-relief boreholes, and coupled disturbance. The results show that dynamic loading shortened the first weighting interval of the overburden by 45.5%, while the thicknesses of the caving zone and fracture zone increased to 15 cm and 42 cm, respectively, representing increases of 36.4% and 20.6% relative to the baseline condition. At the fully mined stage, fracture connectivity increased to 45%. A fracture intersection angle of <50°, connectivity of >40%, and abrupt aperture variation can be regarded as empirical semi-quantitative precursor indicators of a dynamic instability tendency in thick and hard overburden. By introducing prefabricated weak planes, roof pre-splitting guided the directional development of fractures and caving. Under coupled disturbance, the thickness of the fracture zone was reduced by 42.9% compared with that under dynamic disturbance alone, and the amplitude of displacement fluctuation decreased by 33.3%. These changes promoted a transition in overburden movement from an “unordered dislocation” state to a controllable state of “dynamic-disturbance-induced, directionally regulated stability”. These findings provide an experimental basis for early warning and prevention of overburden instability under far-field strong dynamic disturbance in western mining areas with thick and hard overburden. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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24 pages, 30428 KB

Open AccessArticle

Ultrasonic Transmission Experiment Research on Igneous Rocks Under Dry and Saturated Conditions

by Jiaxing Sun, Yuying Zhao and Jingpeng Wang

Appl. Sci. 2026, 16(12), 5869; https://doi.org/10.3390/app16125869 - 10 Jun 2026

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Abstract

To investigate changes in seismic wave propagation in different types of igneous rocks under dry and water-saturated conditions, this study employed CT scanning to characterize the microstructural development of three distinct igneous rock types. Laboratory measurements were then performed to determine the density, [...] Read more.

To investigate changes in seismic wave propagation in different types of igneous rocks under dry and water-saturated conditions, this study employed CT scanning to characterize the microstructural development of three distinct igneous rock types. Laboratory measurements were then performed to determine the density, porosity, permeability, and compressional and shear wave travel times of the rock cores in both dry and water-saturated states. The results show that water content significantly affects the waveforms in both the time and frequency domains. For rocks with developed pores and fractures, the propagation of seismic wave energy is impeded under water-saturated conditions, causing faster attenuation of ultrasonic waves while high-frequency components are retained. For dense rocks, the amplitude of the initial wave segment decreases, the middle-segment amplitude increases, and the tail wave undergoes significant attenuation under saturated conditions, with frequency components in the 50–100 kHz range being filtered out. Furthermore, higher water content leads to lower shear-wave amplitudes and more severe attenuation. These findings contribute to the proper use of acoustic logging data for understanding the microstructure and water content characteristics of igneous rock reservoirs. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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17 pages, 2514 KB

Open AccessArticle

Study on the Instability Process of Coal Seam Wellbores Based on the Coupling of Weakness Plane Strength Criterion and Wellbore Stress

by Fei Wen, Xiaochen Li, Leilei Wang, Jiahui Shi, Junxiong Zhao and Taiheng Yin

Processes 2026, 14(8), 1267; https://doi.org/10.3390/pr14081267 - 16 Apr 2026

Viewed by 417

Abstract

Coal is inherently soft, characterized by well-developed cleat systems, low strength, and significant anisotropy. Existing models that treat coal as a continuous medium or consider only a single plane of weakness fail to capture the synergistic effects of multiple weaknesses on wellbore instability. [...] Read more.

Coal is inherently soft, characterized by well-developed cleat systems, low strength, and significant anisotropy. Existing models that treat coal as a continuous medium or consider only a single plane of weakness fail to capture the synergistic effects of multiple weaknesses on wellbore instability. This study addresses this gap by integrating the strength criteria of weakness planes with wellbore stress theory. First, in situ stresses were transformed into the coordinate system of the weakness planes to derive the acting stress components. A strength criterion incorporating multiple structural planes—accounting for the coal matrix, bedding, face cleats, and butt cleats—was then applied to establish a coupled wellbore stability criterion. A corresponding collapse pressure program was developed using Visual Basic to analyze the effects of stress state, wellbore trajectory, and weakness orientation. The results show that the presence of multiple weakness planes significantly increases the sensitivity of wellbore stability to trajectory. Drilling parallel to the direction of minimum horizontal stress minimizes shear stress and collapse pressure, whereas drilling at high angles or parallel to the maximum horizontal stress activates the weakness planes, leading to a sharp increase in collapse pressure. The presence of these weaknesses results in a highly non-uniform and direction-dependent collapse pressure distribution, with their synergistic interactions further exacerbating the risk of localized failure. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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20 pages, 6028 KB

Open AccessArticle

Grain-Scale Heterogeneity, Fracture Competition, and Non-Planar Propagation in Crystalline Rocks: Insights from a Hydro-Mechanical Phase-Field Model

by Gen Zhang, Cheng Zhao, Zejun Tian, Jinquan Xing, Jialun Niu, Zhaosen Wang and Wenkang Yu

Minerals 2026, 16(3), 339; https://doi.org/10.3390/min16030339 - 23 Mar 2026

Viewed by 489

Abstract

Grain-scale heterogeneity strongly influences hydraulic fracture initiation and trajectory in crystalline rocks, yet its contributions to non-planar growth and the interaction of multiple nearby cracks remain insufficiently quantified. To address this gap, we perform numerical experiments on a model containing two parallel pre-existing [...] Read more.

Grain-scale heterogeneity strongly influences hydraulic fracture initiation and trajectory in crystalline rocks, yet its contributions to non-planar growth and the interaction of multiple nearby cracks remain insufficiently quantified. To address this gap, we perform numerical experiments on a model containing two parallel pre-existing cracks using a hydro-mechanical phase-field framework, systematically quantifying how mineral distribution and axial compression govern non-planar hydraulic fracture growth and inter-fracture competition. The results demonstrate that mineral distribution is the primary driver of fracture complexity. Even within the same Voronoi tessellation, redistributing minerals alone yields markedly different trajectories, deflections, branching patterns, and final morphologies. Furthermore, non-planar growth follows a stepwise, energy-threshold-driven mechanism. When cracks penetrate strong grains or undergo large-angle deflections, propagation is impeded, and injection pressure builds up. Once a critical energy threshold is reached, accumulated energy is rapidly released along the path of minimum incremental energy, manifested as abrupt pressure drops and rapid crack advance. Additionally, the two nearby fractures exhibit strong mechanical competition. Despite negligible hydraulic interference in low-permeability granite, early growth of one fracture redistributes stresses and suppresses the driving force of the other, resulting in asymmetric development. Finally, axial compression primarily governs the overall propagation orientation and influences local failure modes but has a limited effect on peak pressure relative to mineral distribution. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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17 pages, 3914 KB

Open AccessArticle

Study on the Mechanism of Mechanical Strength Modification in Weakly Cemented Sandstone by Silica Sol Grouting

by Wenjie Luo, Honglin Liu, Haitian Yan, Chengfang Shan, Feiteng Zhang and Hongzhi Wang

Processes 2026, 14(6), 930; https://doi.org/10.3390/pr14060930 - 15 Mar 2026

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Abstract

This study addresses the challenges posed by weakly cemented strata in mine tunnels, where surrounding rock softens and deforms upon water exposure, which promotes the development of seepage pathways, and exhibits insufficient stability in bolt (cable) support systems. This study conducts laboratory grouting [...] Read more.

This study addresses the challenges posed by weakly cemented strata in mine tunnels, where surrounding rock softens and deforms upon water exposure, which promotes the development of seepage pathways, and exhibits insufficient stability in bolt (cable) support systems. This study conducts laboratory grouting tests using silica sol on typical weakly cemented sandstone from Xinjiang mining areas. The mineral composition and pore structure were characterized using XRD, SEM, and mercury porosimetry. The injectable mixing ratio parameters for silica sol and the catalyst were determined through viscosity-time evolution tests. Grouting was performed using a custom-built constant-pressure grouting apparatus. After curing, unconfined compressive strength (UCS) and porosity-permeability tests were conducted to evaluate the micro-mechanism of grouting effects on the mechanical and permeability properties of weakly cemented sandstone. The results indicate: (1) The sandstone exhibits a high clay mineral content of 39.8%, dominated by illite. Its pores are primarily small-scale (10–100 nm), accounting for 79.31% of the total pore volume. This scale matches that of silica sol nanoparticles (approximately 9–20 nm), facilitating slurry penetration into micro-pores; (2) microscopic analyses reveal that silica sol effectively reconstructs pore structures through permeation filling and surface coating. Compared to KCl-induced gelation (with approximately 8% gel coverage), NaCl-induced gelation forms a more continuous gel film with more complete pore filling, achieving coverage of around 22%. Furthermore, the larger surface area of the gel aggregates indicates a more thorough filling of micro- and nano-pores, effectively enhancing rock mass compactness. (3) Permeability decreased from 6.91 mD to 3.55 mD, a reduction of 48.6%, while porosity decreased from 16.94% to 13.55%, showing a phased reduction during the grouting process; (4) following pressure grouting stabilization, the uniaxial compressive strength of sandstone increased appropriately by approximately 7–14%, while the elastic modulus rose by about 18–28%. The failure mechanism shifted from shear brittleness to a shear-tension composite state, with enhanced post-peak bearing capacity. These findings provide support for optimizing silica sol grouting parameters in weakly cemented strata tunnels and for the synergistic reinforcement of rock mass permeability and strength. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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20 pages, 5517 KB

Open AccessArticle

Experimental Research on the Supercooling and Freezing Temperatures of Unsaturated Soil

by Jihao Sun, Xiaojie Yang and Yilin Yue

Appl. Sci. 2026, 16(4), 2140; https://doi.org/10.3390/app16042140 - 22 Feb 2026

Viewed by 819

Abstract

With the development of polar regions and the deepening utilization of cold region resources, a large number of infrastructure projects are continuously being carried out. The freezing temperature of unsaturated soil is a critical factor governing the freezing depth and stability of foundations [...] Read more.

With the development of polar regions and the deepening utilization of cold region resources, a large number of infrastructure projects are continuously being carried out. The freezing temperature of unsaturated soil is a critical factor governing the freezing depth and stability of foundations in cold regions or seasons. Concurrently, the supercooling state of soil significantly influences the assessment of its phase composition and physico-mechanical properties. This study employed physical experiments, theoretical formulas, and numerical simulations to reveal the influencing factors and underlying mechanisms of supercooling characteristics in unsaturated soils under controlled low-rate continuous cooling conditions. The results demonstrate that a reduced temperature gradient between the sample surface and the ambient environment correlates with a lower supercooling limit temperature and an extended supercooling duration. An excessively high cooling rate suppresses the supercooling phenomenon in the sample core due to boundary effects. In contrast, neither the temperature difference nor the external cooling rate exhibit a negligible influence on the freezing temperature. Analysis of the temperature–time curves reveals that the freezing process of silty clay is more stable, exhibiting fewer stepwise temperature declines during the phase change plateau, whereas mudstone shows heightened sensitivity to variations in the thermal gradient. Compared to conventional thermocouple measurements, the proposed methodology achieves an optimal balance between temporal efficiency and measurement accuracy. It not only enhances experimental controllability and data reliability, but also provides more scientific theoretical support and technical pathways for predicting freezing depth, designing foundation thermal systems, and preventing frozen ground disasters in cold region engineering. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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22 pages, 7511 KB

Open AccessArticle

Study on the Influence of Rock Pore Structure on Radon Diffusion Coefficient and Permeability Based on Quartet Structure Generation Set Method

by Yuan-Chao Chen, Zhong-Luo Liao and Dong Xie

Processes 2026, 14(4), 634; https://doi.org/10.3390/pr14040634 - 12 Feb 2026

Cited by 1 | Viewed by 473

Abstract

As pore space serves as the primary migration pathway of radon in rock media, investigating the influences of pore structural characteristics on radon migration is essential. In this study, the rock pore structure was numerically reconstructed via the Quartet Structure Generation Set (QSGS) [...] Read more.

As pore space serves as the primary migration pathway of radon in rock media, investigating the influences of pore structural characteristics on radon migration is essential. In this study, the rock pore structure was numerically reconstructed via the Quartet Structure Generation Set (QSGS) method, based on the characteristic parameters extracted from real rock pore models obtained from CT scanning. Quantitative comparison results indicate that the permeability and radon diffusion coefficient of the QSGS-reconstructed models are highly consistent with those of the CT-based model, which verifies the reliability and effectiveness of the QSGS method. A series of three-dimensional (3D) rock pore models with different porosities (η), distribution probabilities (Pd), and growth probabilities (G) were constructed using the QSGS method. The radon diffusion coefficient, tortuosity factor and permeability of these models under dry conditions were quantitatively determined. The relationship between the radon diffusion coefficient, water saturation and temperature was obtained using the tortuosity factor of the pore models and the unsaturated non-isothermal radon diffusion coefficient model. Furthermore, the relationship between the relative permeability of the air and water phases and water saturation was obtained by coupling the calculated permeability with the Brooks–Corey model. The results demonstrate that the η was positively correlated with both the radon diffusion coefficient and permeability, with a more pronounced positive correlation observed for permeability. Under low η conditions, Pd was positively correlated with both the radon diffusion coefficient and permeability; under medium-porosity conditions, Pd was positively correlated with the radon diffusion coefficient but negatively correlated with permeability; under high-porosity conditions, Pd exhibited no significant correlation with the radon diffusion coefficient, while it shows a negative correlation with permeability. G in the principal direction was positively correlated with the radon diffusion coefficient and permeability along the same direction, but negatively correlated with those along orthogonal directions. The radon diffusion coefficient was strongly negatively correlated with water saturation, and weakly positively correlated with temperature. With an increase in water saturation, the relative air permeability presented a nonlinear decrease characterized by a fast-then-slow trend, whereas the relative water permeability showed a nonlinear increase with a slow-then-fast pattern. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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24 pages, 6430 KB

Open AccessArticle

Study on Deep Hole Blasting for Roof Cutting, Pressure Relief and Roadway Protection in Deep Multi-Coal Seam Mining

by Zhongyuan Ren and Mengxiang Wang

Appl. Sci. 2025, 15(18), 10138; https://doi.org/10.3390/app151810138 - 17 Sep 2025

Cited by 3 | Viewed by 929

Abstract

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 [...] Read more.

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

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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18 pages, 2054 KB

Open AccessArticle

An Experimental Study on the Expansion Rate of Blasting Cracks in Prefabricated Grooved Concrete Under Vertical Stresses

by Mengxiang Wang and Qian Dong

Appl. Sci. 2025, 15(17), 9747; https://doi.org/10.3390/app15179747 - 4 Sep 2025

Viewed by 986

Abstract

With the advancement of deep engineering (e.g., deep resource development, tunnel excavation), the deep rock mass is in a high in situ stress environment, leading to a critical engineering challenge: traditional blasting often causes disordered blast-induced crack propagation (severe deviation from the target [...] Read more.

With the advancement of deep engineering (e.g., deep resource development, tunnel excavation), the deep rock mass is in a high in situ stress environment, leading to a critical engineering challenge: traditional blasting often causes disordered blast-induced crack propagation (severe deviation from the target direction) and unstable expansion rates, which reduce the directional blasting efficiency, trigger over-excavation/under-excavation, and threaten construction safety. Water jet notching is a promising directional control technique, but its coupling effect with vertical stress (a dominant component of in situ stress) on blasting crack characteristics remains unclear—hindering its application in deep engineering. To address this problem, reveal the law of blasting crack expansion in deep rock, explore the mechanism of controlled blasting for deep rock fractures, and clarify the effect of deep environmental water jet notching on the blasting effect, this study carried out experimental research on the crack extension velocity of the directional blasting of prefabricated grooved concrete under vertical stress (based on the crack extension strain gauge test system and perimeter pressure loading system) and verified the results by numerical simulations. The main conclusions are as follows: (1) Within the experimental test range, with the increase in vertical stress, the deviation of cracks from the prefabricated groove center in the vertical direction gradually decreases, indicating that vertical stress can further guide the direction of the crack extension on the basis of prefabricated grooves. (2) The experimentally measured crack expansion velocity shows a decreasing trend with the increase in the crack expansion length; the average crack expansion velocity is enhanced with the increase in vertical stress, while the change in the crack tip velocity is suppressed as a whole and gradually tends to be flat at approximately 555.6 m/s. (3) Numerical simulation results (using a model replicating the experimental concrete specimens) further verify the accuracy of the experimental results: the increase in vertical stress further guides the vertical crack expansion, enhances the average crack expansion velocity, and slows down the decay of the crack extension velocity. The core value of this research lies in “converting theoretical experimental data into engineering control capabilities.” Its findings can be directly applied to key areas such as deep resource development, tunnel engineering, and water conservancy projects. While ensuring engineering safety, improving efficiency, and reducing costs, it also provides scientific support for engineering construction in complex geological conditions. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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35 pages, 22649 KB

Open AccessArticle

Research on the Self-Organized Criticality and Fracture Predictability of Sandstone via Real-Time CT Scanning and AE Monitoring

by Huimin Yang, Yongjun Song, Jianxi Ren and Yiqian Chen

Appl. Sci. 2025, 15(11), 6205; https://doi.org/10.3390/app15116205 - 31 May 2025

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Abstract

Progressive damage evolution in rock masses serves as the fundamental mechanism driving geological hazards by controlling deformation patterns and failure predictability. To address the critical challenge of predicting fracture behaviors in heterogeneous geological media, this study pioneers the integration of real-time computed tomography [...] Read more.

Progressive damage evolution in rock masses serves as the fundamental mechanism driving geological hazards by controlling deformation patterns and failure predictability. To address the critical challenge of predicting fracture behaviors in heterogeneous geological media, this study pioneers the integration of real-time computed tomography (CT) scanning and acoustic emission (AE) monitoring to investigate self-organized criticality and fracture predictability in Cretaceous sandstone under uniaxial compression. By systematically analyzing internal structural evolution and damage parameters, this established a multiparameter framework to characterize self-organized processes and critical phase transitions during progressive fracturing. Key findings include the following: (1) Distinct critical thresholds emerge during yield-stage self-organization, marked by abrupt transitions in AE signals and crack metrics—from microdamage coalescence initiating volumetric expansion (first critical point) to macrocrack nucleation preceding peak strength (second critical point). (2) AE-crack evolution follows power–law statistics, where elevated scaling exponents (r > 0.85) correlate with intensified nonlinear damage, accelerated localization, and progressive rate enhancement. Yield-stage power–law acceleration provides quantifiable failure precursors. (3) Yield-stage damage patterns exhibit 85% similarity with terminal failure configurations, confirming yield-stage as the definitive precursor with critical temporal signatures for failure prediction. A conceptual framework integrating multiparameter responses (AE signals, crack metrics) was developed to decipher self-organized critical phase transitions during deformation-failure processes. This work establishes methodological foundations for investigating damage mechanisms and predictive strategies in heterogeneous rock systems. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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22 pages, 5070 KB

Open AccessArticle

Experimental and Modeling Study of Core-Scale Three-Dimensional Rough Fracture Acidic Wastewater Reaction with Carbonate Rocks

by Weiping Yu, Guangfu Duan, Chenyu Zong, Min Jin and Zhou Chen

Appl. Sci. 2025, 15(11), 5944; https://doi.org/10.3390/app15115944 - 25 May 2025

Viewed by 1051

Abstract

Phosphogypsum leachate significantly accelerates carbonate rock dissolution in karst regions. The dissolution mechanism of phosphogypsum leachate associated with carbonate rock interaction and the corresponding numerical simulation need further study. In this study, 3D digital core imaging was used to scan undisturbed carbonate rock [...] Read more.

Phosphogypsum leachate significantly accelerates carbonate rock dissolution in karst regions. The dissolution mechanism of phosphogypsum leachate associated with carbonate rock interaction and the corresponding numerical simulation need further study. In this study, 3D digital core imaging was used to scan undisturbed carbonate rock specimens from phosphogypsum landfill sites, and corresponding 3D structural models were constructed. We carried out indoor dissolution experiments in which we used Scanning Electron Microscopy as well as Energy Dispersive Spectrometer to observe changes in the surface micromorphology and elemental content of the rock specimens under different dissolution conditions. A reactive numerical model was developed based on the 3D structural model obtained from 3D digital core imaging, and numerical simulation studies were conducted. The dissolution reaction between phosphogypsum leachate and carbonate rocks exhibited an initial rapid phase followed by gradual stabilization. The pH of the leachate showed an exponential negative correlation with the dissolution amount per unit area of the rock specimens, while a power-law negative correlation was observed between pH and chemical dissolution rates. The numerical model effectively reproduced the reactant concentration states observed in experiments, confirming its capability to simulate reaction processes within rock specimens. Simulation results demonstrated that preferential flow through fracture channels led to higher reactant concentrations near fractures due to incomplete reactions, whereas lower concentrations occurred in sub-fracture regions. As the fracture aperture increased, the concentration disparity between these regions became more pronounced, with higher concentration of reactants at the outlet. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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19 pages, 3617 KB

Open AccessArticle

Comparative Evaluation of Presented Strength Criteria of Anisotropic Rocks Based on Triaxial Experiments

by Yongfeng Liu, Zhengxing Yu, Yongming Yin and Jinglin Wen

Appl. Sci. 2025, 15(10), 5308; https://doi.org/10.3390/app15105308 - 9 May 2025

Cited by 3 | Viewed by 1529

Abstract

The inherent mineralogical alignment in stratified rock formations engenders pronounced mechanical anisotropy, presenting persistent challenges across geological, geotechnical, and petroleum engineering disciplines. While substantial progress has been made in modeling transversely isotropic media, current methodologies exhibit limitations in reconciling theoretical predictions with complex [...] Read more.

The inherent mineralogical alignment in stratified rock formations engenders pronounced mechanical anisotropy, presenting persistent challenges across geological, geotechnical, and petroleum engineering disciplines. While substantial progress has been made in modeling transversely isotropic media, current methodologies exhibit limitations in reconciling theoretical predictions with complex failure mechanisms. This investigation examines the anisotropic response of diverse lithologies through triaxial testing across bedding orientations (0–90°) and confinement levels (0–60 MPa), revealing a pressure-dependent attenuation of directional strength variations. Experimental evidence identifies three dominant failure modes: cross-bedding shear fracturing, bedding-parallel sliding, and hybrid mechanisms combining both, with transition thresholds governed by confinement intensity and bedding angle. Analytical comparisons demonstrate that conventional single weakness plane models produce characteristic shoulder-shaped strength curves with overpredictions, particularly in hybrid failure regimes. Conversely, the modified patchy weakness plane formulation achieves superior predictive accuracy through parametric representation of anisotropy gradation, effectively capturing strength transitions between end-member failure modes. The Pariseau criterion, though marginally less precise in absolute terms, provides critical insights into directional strength contrasts through its explicit differentiation of vertical versus parallel bedding responses. These findings advance the fundamental understanding of anisotropic rock behavior while establishing practical frameworks for optimizing stability assessments in bedded formations, particularly in high-confinement environments characteristic of deep reservoirs and engineered underground structures. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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16 pages, 16719 KB

Open AccessArticle

Experimental Study on Plugging of Micro-Leakage Interlayer (MLI) in Underground Salt Cavern Gas Storage (Jintan, China)

by Hongwu Yin and Xinbo Ge

Processes 2025, 13(4), 1188; https://doi.org/10.3390/pr13041188 - 14 Apr 2025

Viewed by 1025

Abstract

The permeability of a certain mudstone interlayer in underground salt cavern gas storage (Jintan, China) is slightly high, as indicated by pressure tests (leakage rate of approximately 1~2 L/d). This layer is referred to as the “Micro-Leakage Interlayer (MLI)”. The MLI significantly impacts [...] Read more.

The permeability of a certain mudstone interlayer in underground salt cavern gas storage (Jintan, China) is slightly high, as indicated by pressure tests (leakage rate of approximately 1~2 L/d). This layer is referred to as the “Micro-Leakage Interlayer (MLI)”. The MLI significantly impacts the tightness of gas storage, potentially leading to substantial losses. To address this problem, an experimental study was conducted. Initially, a method utilizing brine crystallization to plug the micro-leakage interlayer (MLI) was proposed. After crystallization, the porosity of the MLI cores exhibited a notable increase, and the permeability of the MLI cores increased significantly, further exacerbating the risk of gas leakage. These results indicate that the plugging solution requires further exploration. Finally, a combined plugging solution utilizing brine crystallization and ultrafine cement was proposed. Using saturated brine and waterproof coatings, an ultrafine cement slurry was prepared, and specimens were created for testing. The results indicate that the specimens exhibited a porosity of approximately 3%, a permeability below 10⁻¹⁹ m², and a uniaxial compressive strength of about 40 MPa. The ultrafine cement particles had an average particle size of 3 µm, and the ultrafine cement slurry exhibited extremely low porosity and permeability, as well as high strength. The results indicate that this solution is highly feasible and can be applied to field engineering. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions, 2nd Edition)

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