Complex Rock Mechanics Problems and Solutions

Topic Information

Dear Colleagues,

The purpose behind the birth of rock mechanics was to solve rock engineering stability problems and study rock crushing conditions. The research medium is very complex, and there are many unstable or uncertain factors associated with mechanical properties, which make it difficult to establish an independent, complete and systematic theoretical basis for this discipline. The development of rock mechanics has always used the basic theories and research results of solid mechanics, soil mechanics, engineering geology and other disciplines to solve the problems of geotechnical engineering. Therefore, rock mechanics that emphasize different industries often have different definitions. Due to the extensiveness of the service objects of rock mechanics and the complexity of the research objects, it has been concluded that the research content of rock mechanics must also be extensive and complex. We, therefore, invite papers on innovative technical developments, in addition to reviews, case studies and analytical and assessment papers from different disciplines that are relevant to the topic of rock mechanics. The main topics of the section include, but are not limited to, the following:

• Simulation, mechanical expression and mechanical mechanism of rock mass structure and structural plane;
• The strength, failure mechanism and failure criterion of fractured rock mass;
• Interaction and stability evaluation of rock mass and engineering structure;
• Mechanical properties of soft rock and its rock mass mechanics;
• Water-rock-stress coupling effect and rock mass engineering stability;
• High in-situ stress rock mass mechanics;
• The overall comprehensive simulation feedback system and optimization technology of rock mass structure;
• Rock mass dynamics, thermodynamics and hydraulic problems;
• Rock mass rheology and long-term strength;
• Computer-aided design of rock mass engineering and automatic image generation processing.

Prof. Dr. Chun Zhu
Prof. Yujun Zuo
Prof. Dr. Shibin Tang
Dr. Qian Yin
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	17.8 Days	CHF 2400
Energies energies	3.0	6.2	2008	17.5 Days	CHF 2600
Geosciences geosciences	2.4	5.3	2011	26.2 Days	CHF 1800
Minerals minerals	2.2	4.1	2011	18 Days	CHF 2400
Remote Sensing remotesensing	4.2	8.3	2009	24.7 Days	CHF 2700

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Published Papers (27 papers)

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22 pages, 18661 KiB  

Open AccessArticle

Experimental and Numerical Investigations on the Slate Shearing Mechanical Behavior

by Jinze Gu, Ming Huang, Fuqiang Ren, Chun Zhu, Zhanbo Cheng, Zhengxiong Bai and Zhiyu Song

Appl. Sci. 2024, 14(19), 9104; https://doi.org/10.3390/app14199104 - 9 Oct 2024

Viewed by 675

Abstract

Multi-scale assessment of shear behavior in the tunnel carbonaceous slate is critical for evaluating the stability of the surrounding rock. In this study, direct shear tests were conducted on carbonaceous slates from the Muzhailing Tunnel, considering five bedding dip angles (β) [...] Read more.

Multi-scale assessment of shear behavior in the tunnel carbonaceous slate is critical for evaluating the stability of the surrounding rock. In this study, direct shear tests were conducted on carbonaceous slates from the Muzhailing Tunnel, considering five bedding dip angles (β) and four normal stresses (σ_n). The micro-mechanism was also examined by combining acoustic emission (AE) and energy rate with PFC2D Version 5.0 (particle flow code 2D Version 5.0 software) numerical simulations. The results showed a linear relationship between peak shear stress and normal stress, with the rate of increase inversely related to β. Cohesion increased linearly with β, while internal friction angle and AE activity decreased; the energy release rate is 3.92 × 10⁸ aJ/s at 0° and 1.93 × 10⁸ aJ/s at 90°. Shearing along the preset fracture plane was the main failure mode. Increased normal stress led to lateral cracks perpendicular to or intersecting the shear plane. Cracks along the bedding plane formed a broad shear band with concentrated compressive force, and inclined bedding was accompanied by a dense tension chain along the bedding plane. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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18 pages, 6422 KiB  

Open AccessArticle

Integrating the Finite Element Method with Python Scripting to Assess Mining Impacts on Surface Deformations

by Mateusz Dudek, Dawid Mrocheń, Anton Sroka and Krzysztof Tajduś

Appl. Sci. 2024, 14(17), 7797; https://doi.org/10.3390/app14177797 - 3 Sep 2024

Viewed by 527

Abstract

Mining operations disrupt the structure of rock layers, leading to surface deformations and potential mining damage. This issue has been extensively studied since the 19th century using various analytical, geometric-integral, and stochastic methods. Since the 1990s, numerical methods have been increasingly applied to [...] Read more.

Mining operations disrupt the structure of rock layers, leading to surface deformations and potential mining damage. This issue has been extensively studied since the 19th century using various analytical, geometric-integral, and stochastic methods. Since the 1990s, numerical methods have been increasingly applied to determine changes in the stress and strain states of rock masses due to mining activities. These methods account for numerous additional factors influencing surface deformation, offering significant advantages over classical approaches. However, modelling rock masses presents challenges, particularly in calibrating the mechanical parameters of rock layers, an area extensively researched with numerous publications. In this study, we determined the mechanical parameter values of rock layers at the advancing mining front using a custom Python script and Finite Element Method (FEM) numerical models. We also introduced a modification to evaluate the error of the estimated parameter values. Numerical analyses were conducted for the Piast–Ziemowit mine region in Poland, utilizing mining, geological, and surveying data. Our results demonstrate that accurate calibration of mechanical parameters is crucial for reliable predictions of surface deformations. The proposed methodology enhances the precision of numerical models, providing a more robust framework for assessing the impact of mining activities on rock layers. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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16 pages, 6625 KiB  

Open AccessArticle

Surface Subsidence Modelling Induced by Formation of Cavities in Underground Coal Gasification

by Yuan Jiang, Bingbing Chen, Lin Teng, Yan Wang and Feng Xiong

Appl. Sci. 2024, 14(13), 5733; https://doi.org/10.3390/app14135733 - 1 Jul 2024

Cited by 1 | Viewed by 806

Abstract

Underground coal gasification (UCG) is an efficient method for the conversion of deep coal resources into energy. The scope of this work is to model the subsidence of four gasification cavities with a size of 30 m × 30 m × 15 m, [...] Read more.

Underground coal gasification (UCG) is an efficient method for the conversion of deep coal resources into energy. The scope of this work is to model the subsidence of four gasification cavities with a size of 30 m × 30 m × 15 m, separated by 15 m wide pillars. Two scenarios of gasification sequence are modelled, one with the gasification of cavities 1 and 2 followed by 3 and 4, and the other one with the sequence of cavities 1 and 3, followed by 2 and 4. The results show that the final surface subsidence after gasification of four cavities is 9.8 mm and the gasification sequence has an impact only on the subsidence at the intermediate stage but has no impact on the final subsidence after all four cavities are formed, when only the elasticity regime is considered. Additionally, the maximum surface subsidence for the studied cavities of different sizes ranges from 0.016 mm to 7.14 mm, and the relationship between the subsidence and the cavity volume is approximately linear. Finally, a prediction model of surface subsidence deformation is built up using the elastic plate theory, and the formula of surface deformation at a random point is given. The maximum difference between measured and calculated deformation is 4.6%, demonstrating that the proposed method can be used to predict the ground subsidence induced by UCG. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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13 pages, 3009 KiB  

Open AccessArticle

Strength and Deformation of Pillars during Mining in the Shaft Pillar

by Jindřich Šancer, Vladimír Petroš, Vlastimil Hudeček and Pavel Zapletal

Appl. Sci. 2024, 14(12), 5003; https://doi.org/10.3390/app14125003 - 8 Jun 2024

Cited by 2 | Viewed by 851

Abstract

This study of the strength and deformation of coal samples was triggered by the need to define the stress–strain characteristics of pillars during room and pillar mining in the shaft protective pillar at the ČSM Mine. It was probably the world’s deepest deployment [...] Read more.

This study of the strength and deformation of coal samples was triggered by the need to define the stress–strain characteristics of pillars during room and pillar mining in the shaft protective pillar at the ČSM Mine. It was probably the world’s deepest deployment of this mining method in a coal mine. In order to solve the bearing capacity of pillars, the dependence of coal strength on the slenderness ratio is used. For this reason, coal samples with different slenderness ratios were investigated. After considering the purpose of this research, slenderness ratios (width/height) of 1 to 7.7 were chosen. At the same time, the modulus of deformation as a function of the slenderness ratio was determined, and the vertical deformation of the pillars and the safety factor were calculated. Attention is also paid to the influence of sampling on the results of measured coal strengths. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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24 pages, 9860 KiB  

Open AccessArticle

Research on Mechanical Properties of Steel-Polypropylene Fiber-Reinforced Concrete after High-Temperature Treatments

by Xinggang Shen, Xia Li, Lei Liu, Xinzuo Chen and Jun Du

Appl. Sci. 2024, 14(9), 3861; https://doi.org/10.3390/app14093861 - 30 Apr 2024

Viewed by 944

Abstract

A mechanical property experiment was carried out on steel-polypropylene fiber-reinforced concrete after elevated temperatures by using a 50 mm diameter SHPB apparatus. The regulations of compressive strength, elastic modulus, Poisson’s ratio, and other mechanical properties under six heating temperature levels (normal temperature, 100 [...] Read more.

A mechanical property experiment was carried out on steel-polypropylene fiber-reinforced concrete after elevated temperatures by using a 50 mm diameter SHPB apparatus. The regulations of compressive strength, elastic modulus, Poisson’s ratio, and other mechanical properties under six heating temperature levels (normal temperature, 100 °C, 200 °C, 400 °C, 600 °C, and 800 °C) and three impact pressures (0.3 MPa, 0.4 MPa, 0.5 MPa) were studied. Using ANSYS/LS-DYNA 19.0 numerical simulation software and LS-PrePost post-processing software, numerical simulation analysis was conducted on the dynamic Hopkinson uniaxial impact compression and uniaxial dynamic impact splitting mechanical experiments of C40 plain concrete and steel-polypropylene hybrid fiber concrete. The results show that the dynamic compressive strength of hybrid fiber concrete with the optimal dosage reaches its maximum at a temperature group of 200 °C, and the dynamic compressive strength of hybrid fiber concrete with the optimal dosage increases by 97.1% compared to C40 plain concrete at a temperature group of 800 °C. The impact waveform and stress-strain curve results of the numerical simulation are very similar to the experimental results. The errors in calculating the peak stress and peak strain are within 6%, which can truly and accurately simulate the static mechanical properties and failure process of hybrid fiber-reinforced concrete. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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21 pages, 18737 KiB  

Open AccessArticle

Research on the Laws of Overlying Rock Fracture and Energy Release under Different Mining Speeds

by Xin Yu, Mingshi Gao, Hongchao Zhao, Shifan Zhao and Huashan Zhao

Appl. Sci. 2024, 14(8), 3222; https://doi.org/10.3390/app14083222 - 11 Apr 2024

Cited by 1 | Viewed by 785

Abstract

Mining activities are key triggers for strong mine earthquakes and even rock bursts in coal mines. This study explores the impact of mining speed on the overlying strata’s deformation and energy release through theoretical analysis, numerical simulation, and the digital speckle method. The [...] Read more.

Mining activities are key triggers for strong mine earthquakes and even rock bursts in coal mines. This study explores the impact of mining speed on the overlying strata’s deformation and energy release through theoretical analysis, numerical simulation, and the digital speckle method. The temporal and spatial evolution characteristics of the impact energy during mining are simulated. The digital speckle method illustrates a positive correlation between rapid mining and increased fracture block degree of overburden rock and roof separation, confirming that accelerated mining speed extends the fracture distance of the stope. Furthermore, numerical simulations establish that both the energy associated with overlying rock breaking and the frequency of energy occurrence events are amplified during rapid mining, in contrast to slow mining. This observation corroborates that escalating mining speed augments the energy dispensed by the breaking of the upper rock. Consequently, this escalation induces a transformation in the energy levels of mine earthquakes, culminating in a heightened incidence of large-energy mine earthquakes. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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19 pages, 14552 KiB  

Open AccessArticle

Visualized Hydraulic Fracture Re-Orientation in Directional Hydraulic Fracturing by Laboratory Experiments in Gelatin Samples

by Hua Zhang, Benben Liu and Qingyuan He

Appl. Sci. 2024, 14(5), 2047; https://doi.org/10.3390/app14052047 - 29 Feb 2024

Viewed by 903

Abstract

Directional hydraulic fracturing (DHF) is popular with hydraulic fracturing operations in coal mining to create cave-hard roofs, in which radial initial notches are created around open borehole walls before injecting high-pressurized fluid. Despite extensive field application of DHF, the three-dimensional irregular hydraulic fracture [...] Read more.

Directional hydraulic fracturing (DHF) is popular with hydraulic fracturing operations in coal mining to create cave-hard roofs, in which radial initial notches are created around open borehole walls before injecting high-pressurized fluid. Despite extensive field application of DHF, the three-dimensional irregular hydraulic fracture (HF) geometry in DHF remains unclear, and the HF re-orientation mechanism requires comprehensive understanding. Here, we experimentally examined factors affecting HF re-orientation in DHF in transparent gelatin samples with a self-developed experimental device. We found that it is the ratio between the differential stress and gelatin elastic moduls that determines HF re-orientation rather than the absolute magnitudes of these two factors. Both shear failure and tensile failure occur during HF re-orientation. The HF tends to propagate asymmetrically, and the step-like HF geometry is likely to form in gelatin samples with low elastic moduli and under high differential stresses. HF re-orientation is not necessarily a near-borehole effect, and HFs can propagate along the notch direction for longer distances in stiffer gelatin samples under relatively low or moderate differential stresses. Finally, recommendations are provided for the effective utilization of DHF at coal mine sites. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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13 pages, 4251 KiB  

Open AccessArticle

Investigation into Influences of Hydraulic Fracturing for Hard Rock Weakening in Underground Mines

by Xu Cao, Saisai Wu and Qingyuan He

Appl. Sci. 2024, 14(5), 1948; https://doi.org/10.3390/app14051948 - 27 Feb 2024

Cited by 1 | Viewed by 999

Abstract

The long overhanging distance of hard roofs and long-collapse steps induces a large area of suspension on the working face in underground coal mines, resulting in excessive pressure and deformation on the surrounding rocks of the adjacent roadway in the work face, which [...] Read more.

The long overhanging distance of hard roofs and long-collapse steps induces a large area of suspension on the working face in underground coal mines, resulting in excessive pressure and deformation on the surrounding rocks of the adjacent roadway in the work face, which seriously threatens the safety of coal mining operations. In this study, in order to study the hydraulic fracturing effects on hard roofs, numerical simulation and in situ tests were conducted. The analysis and comparison of fracturing effects under different hydraulic fracturing parameters were carried out, and the reasonable hydraulic fracturing parameters of the hydraulic weakening of hard roofs were designed accordingly. Based on designed hydraulic fracturing, industrial tests were conducted in the field while stress and deformation were recorded. The results show that hydraulic fracturing could effectively reduce the pressure of the hard roof. Hydraulic fracturing effectively destroyed the cantilever beam structure above the coal pillar, reduced the stress concentration, and moderated mineral pressure at the working face. The proposed methods and obtained results provide theoretical and technical support for the treatment of underground mines with hard roofs. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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10 pages, 4316 KiB  

Open AccessTechnical Note

An Analysis of the Impact of Mining Excavation Velocity on the Development of Gaseous and Gaseous Geodynamic Hazards in Copper Ore Mines

by Maciej Gniewosz, Agnieszka Stopkowicz and Marek Cała

Geosciences 2024, 14(2), 54; https://doi.org/10.3390/geosciences14020054 - 18 Feb 2024

Viewed by 1434

Abstract

The hazards of gaseous geodynamic phenomena and rockbursts are among the most challenging to assess and classify. This perception arises from both a review of the literature and an examination of available instructions and regulations in underground mining facilities. The hazard of gaseous [...] Read more.

The hazards of gaseous geodynamic phenomena and rockbursts are among the most challenging to assess and classify. This perception arises from both a review of the literature and an examination of available instructions and regulations in underground mining facilities. The hazard of gaseous geodynamic phenomena in Polish copper ore mines only appeared in 2009, whereas these phenomena occur and are commonly described in other mining countries. In Polish copper ore mines, due to the room and pillar system in fields with lengths of about 460 m, very often parallel to neighboring fields, which together give a length of about 900 m, it is difficult to identify the location of gas traps due to the large size of the area. This paper presents an analysis of the influence of the velocity of the excavation on the possibility of escalating or reducing the described mining hazards. An analysis of the impact of excavation velocity on the state of gaseous geodynamic and roof fall hazards was conducted for two mining fields. For the considered mining fields, the hypothesis was formulated that an excavation velocity greater than or equal to 17 m/month positively influences a reduction in both gaseous geodynamic and roof fall hazards. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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24 pages, 14067 KiB  

Open AccessArticle

Automatic Characterization of Block-In-Matrix Rock Outcrops through Segmentation Algorithms and Its Application to an Archaeo-Mining Case Study

by Andrés Cristóbal, Xurxo Rigueira, Ignacio Pérez-Rey, Xian Estévez-Ventosa, María Pazo, Maria Lia Napoli, Brais X. Currás and Leandro R. Alejano

Geosciences 2024, 14(2), 29; https://doi.org/10.3390/geosciences14020029 - 26 Jan 2024

Cited by 1 | Viewed by 2632

Abstract

The mechanical behavior of block-in-matrix materials is heavily dependent on their block content. This parameter is in most cases obtained through visual analyses of the ground through digital imagery, which provides the areal block proportion (ABP) of the area analyzed. Nowadays, computer vision [...] Read more.

The mechanical behavior of block-in-matrix materials is heavily dependent on their block content. This parameter is in most cases obtained through visual analyses of the ground through digital imagery, which provides the areal block proportion (ABP) of the area analyzed. Nowadays, computer vision models have the capability to extract knowledge from the information stored in these images. In this research, we analyze and compare classical feature-detection algorithms with state-of-the-art models for the automatic calculation of the ABP parameter in images from surface and underground outcrops. The outcomes of this analysis result in the development of a framework for ABP calculation based on the Segment Anything Model (SAM), which is capable of performing this task at a human level when compared with the results of 32 experts in the field. Consequently, this model can help reduce human bias in the estimation of mechanical properties of block-in-matrix materials as well as contain underground technical problems due to mischaracterization of rock block quantities and dimensions. The methodology used to obtain the ABP at different outcrops is combined with estimates of the rock matrix properties and other characterization techniques to mechanically characterize the block-in-matrix materials. The combination of all these techniques has been applied to analyze, understand and try, for the first time, to model Roman gold-mining strategies in an archaeological site in NW Spain. This mining method is explained through a 2D finite-element method numerical model. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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21 pages, 9822 KiB  

Open AccessArticle

Predicting Temperature and Humidity in Roadway with Water Trickling Using Principal Component Analysis-Long Short-Term Memory-Genetic Algorithm Method

by Dong Wu, Zhichao Jia, Yanqi Zhang and Junhui Wang

Appl. Sci. 2023, 13(24), 13343; https://doi.org/10.3390/app132413343 - 18 Dec 2023

Cited by 1 | Viewed by 1175

Abstract

The heat dissipated from high geo-temperature underground surrounding rocks is the main heat source of working faces, while thermal water upwelling and trickling into the roadway will notably deteriorate the mine’s climate and thermal comfort. Predicting airflow temperature and relative humidity (RH) is [...] Read more.

The heat dissipated from high geo-temperature underground surrounding rocks is the main heat source of working faces, while thermal water upwelling and trickling into the roadway will notably deteriorate the mine’s climate and thermal comfort. Predicting airflow temperature and relative humidity (RH) is conductive to intelligent control of air conditioning cooling and ventilation regulation. To accommodate this issue, an intelligent technique was proposed, integrating a genetic algorithm (GA) and long short-term memory (LSTM) based on rock temperature, inlet air temperature, water temperature, water flow rate, RH, and ventilation time. A total of 21 input features including over 200 pieces of data were collected from an independently developed modeling roadway to construct a dataset. Principal component analysis (PCA) was conducted to reduce features, and GA was used to tune the LSTM and PCA-LSTM architectures for best performance. The following research results were yielded. The proposed PCA-LSTM-GA model is more reliable and efficient than the single LSTM model or hybrid LSTM-GA model in predicting the air temperature $T_{f_{out}}$ and humidity ${RH}_{out}$ at the end of the water trickling roadway. The importance scores (ISs) indicate that $T_{f_{out}}$ is mainly influenced by the surrounding rock temperature (IS 0.661) and the inlet air temperature (IS 0.264). While ${RH}_{out}$ is primarily influenced by the rock temperature in the water trickling section (IS 0.577), the inlet air temperature (IS 0.187), and the trickling water temperature and flow rate (total IS 0.136), and it has an evident time effect. In addition, we developed relevant equipment and provided engineering practice methods to use the machine learning model. The proposed model, which can predict the mine microclimate, serves to facilitate coal and geothermal resource co-mining as well as thermal hazard control. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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19 pages, 9250 KiB  

Open AccessArticle

Improved Computer Vision Framework for Mesoscale Simulation of Xiyu Conglomerate Using the Discrete Element Method

by Yutao Zhang, Zijie He, Ruonan Jiang, Lei Liao and Qingxiang Meng

Appl. Sci. 2023, 13(24), 13000; https://doi.org/10.3390/app132413000 - 5 Dec 2023

Cited by 1 | Viewed by 1340

Abstract

The complex mechanical characteristics of the Xiyu conglomerate significantly influence the resistance and deformation features of its caverns’ surrounding rock, thereby constraining the construction of related water diversion tunnels. This paper introduces an improved SegFormer framework developed for the detection of mesoscale geomaterial [...] Read more.

The complex mechanical characteristics of the Xiyu conglomerate significantly influence the resistance and deformation features of its caverns’ surrounding rock, thereby constraining the construction of related water diversion tunnels. This paper introduces an improved SegFormer framework developed for the detection of mesoscale geomaterial structures. Computerized tomography (CT) scan images of the Xiyu conglomerate were employed to establish a high-precision numerical model. From the results of segmentation, the proposed algorithm outperformed UNet, HRNet, and the original SegFormer neural network. The segmentation results were used to calculate the porosity, and biaxial compression numerical simulation experiments based on the real structure were carried out using the particle flow code (PFC). We observed the failure process of the model and obtained the shear strength of the Xiyu conglomerate. We explored the causes and influencing factors of the anisotropy of the Xiyu conglomerate from the microstructure perspective and provide a micro-observation basis for establishing an anisotropic mechanical model. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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18 pages, 6311 KiB  

Open AccessArticle

Stability Analysis of Trench Wall for Diaphragm Wall in Ultra-Deep Circular Foundation Pit: A Comprehensive Investigation

by Qianwei Xu, Jinli Xie, Zili Sun, Linhai Lu and Hangfei Yu

Appl. Sci. 2023, 13(21), 12037; https://doi.org/10.3390/app132112037 - 4 Nov 2023

Cited by 2 | Viewed by 2665

Abstract

Circular diaphragm walls are increasingly being used in ultra-deep foundation pits due to their arch-shaped bearing system, which provides reasonable structural support. The trench walls that form the circular ground connection wall are typically double-angled in shape, and their stability analysis remains a [...] Read more.

Circular diaphragm walls are increasingly being used in ultra-deep foundation pits due to their arch-shaped bearing system, which provides reasonable structural support. The trench walls that form the circular ground connection wall are typically double-angled in shape, and their stability analysis remains a challenge. In this paper, an instability model for double-angled trench walls based on 3D sliding body analysis is proposed. The objective of this paper is to determine the minimum amount of slurry needed to maintain the integrity of the trench wall. The results show that the center of symmetry on the inside of the wall is the most vulnerable to damage, followed by the inside corner, and then the center and corner on the outside. The consideration of sliding bodies in overall and local stability calculations for double-angled trench wall shapes can provide a reasonable stability assessment. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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17 pages, 2499 KiB  

Open AccessArticle

Theoretical Study of Large Uncoupling Coefficient Loading for Surface Blasting

by Mengxiang Wang, Haibo Wang, Qi Zong, Feng Xiong, Qian Kang, Chun Zhu and Yuanyuan Pan

Appl. Sci. 2023, 13(20), 11582; https://doi.org/10.3390/app132011582 - 23 Oct 2023

Cited by 2 | Viewed by 999

Abstract

Smooth surface blasting control technology is aimed at blasting the rock body until it is left with a smooth surface and to protect it from damage; the current air spaced axial uncoupled charge and air spaced radial uncoupled continuous charge are effective charging [...] Read more.

Smooth surface blasting control technology is aimed at blasting the rock body until it is left with a smooth surface and to protect it from damage; the current air spaced axial uncoupled charge and air spaced radial uncoupled continuous charge are effective charging structures for smooth surface blasting. Reserved air spacing can effectively reduce the blast wave and the peak pressure of the explosive gas, improving the quasi-static pressure of the explosive gas under the action of rock surface blasting with fracture seam quality. In order to ensure the effect of surface blasting, small-diameter light surface holes are more often used; with the development of drilling machinery, the use of large-diameter light blast holes with an oversized uncoupled coefficient of loading structure effectively improves the efficiency of the construction and at the same time achieves better blasting results. However, according to the bursting assumption of obtaining the theory of light surface blasting in the application of large uncoupling coefficient loading, light surface blasting has certain limitations. In this regard, the bursting theory explores the air spacing uncoupling charge in line with the multi-faceted exponential expansion of the critical uncoupling coefficient and is in accordance with the following: the requirements of light surface blasting and the field loading structure; the derivation of the quasi-static pressure on the wall of the gunhole under the action of large uncoupling, uncoupling coefficient, and the parameters of the spacing between the gunholes; the establishment of the axial uncoupling coefficient and the radial uncoupling coefficient-equivalent relationship between the uncoupling coefficient and the theoretical relationship between the selection of the spacing between the holes; the uncoupling coefficient and the selection of the theoretical relationship between the spacing between the holes. This study reveals the mechanism by which different parameters of surface blasting can achieve good results in engineering practices. A slope in Guizhou is an example of sample calculations and the application of two different charging structures applied to field loading, which have achieved good surface blasting results. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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16 pages, 5052 KiB  

Open AccessArticle

Limit Equilibrium Models for Tunnel Face Stability in Composite Soft-Hard Strata

by Xiao Zhang, Qilong Song, Zhanhu Yao, Dong Su, Yazhou Zhang and Qiang Li

Appl. Sci. 2023, 13(19), 10748; https://doi.org/10.3390/app131910748 - 27 Sep 2023

Viewed by 1092

Abstract

The tunnel face stability in composite strata, commonly referred to as the soft upper and hard lower condition, is a critical challenge in tunnel construction. The soft–hard ratio (SA) strongly influences the limit support pressure as well as the failure mechanism experienced by [...] Read more.

The tunnel face stability in composite strata, commonly referred to as the soft upper and hard lower condition, is a critical challenge in tunnel construction. The soft–hard ratio (SA) strongly influences the limit support pressure as well as the failure mechanism experienced by a tunnel face. This study focused on the Xingye Tunnel project in the Xiangzhou District of Zhuhai City. By conducting numerical simulations, the impact of different SAs on the limit support pressure was investigated. Furthermore, a limit equilibrium model was established on the basis of the analysis of the results of numerical simulation. The findings were then compared and analyzed alongside those of relevant theoretical models. In the event of tunnel face instability of composite strata, the deformation tends to be concentrated mainly in the soft soil layer, with less noticeable deformation in the hard rock layer. The investigation of different SAs revealed a linear decrease in the limit support pressure ratio of the tunnel face in composite strata as SA decreases. The self-stability of the tunnel face was observed when SA ≤ 0.125. Moreover, the limit support pressure ratio predicted by the truncated log-spiral model (TLSM) exhibited a higher degree of agreement with the results of numerical simulation than those of other relevant models. The superiority of TLSM was mainly demonstrated in the range of SA = 0.25 to 1.0. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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19 pages, 5438 KiB  

Open AccessArticle

Creep and Hardening Characteristics of Anthracite under Graded Static–Dynamic Coupled Loading

by Shaofei Yue, Kai Wang, Xiaoqiang Zhang, Tianhe Kang, Jianbing Yan and Yulong Jiang

Appl. Sci. 2023, 13(19), 10648; https://doi.org/10.3390/app131910648 - 25 Sep 2023

Viewed by 786

Abstract

Remaining coal pillars in remining areas exhibit clear creep characteristics, and dynamic pressure accelerates their instability and failure. The creep and hardening characteristics of coal under dynamic pressure are of great engineering significance for the stability of remaining coal pillars in remining areas [...] Read more.

Remaining coal pillars in remining areas exhibit clear creep characteristics, and dynamic pressure accelerates their instability and failure. The creep and hardening characteristics of coal under dynamic pressure are of great engineering significance for the stability of remaining coal pillars in remining areas and their control. To investigate the creep and hardening characteristics of anthracite under static–dynamic coupled loading, graded loading creep tests with different loading rates were conducted. In this research, the creep strain, instantaneous elastic modulus, and creep rate of anthracite were studied under different graded loading rates. The results showed that the hardening effect of the samples manifested as an increasing instantaneous elastic modulus at the loading stage and a decreasing strain rate at the creep stage. When the graded loading rate increases from 0.01 to 0.1 mm/s, the instantaneous elastic modulus increases by 0.16–2.32 times. The sudden increase in the instantaneous elastic modulus at the failure stress level explains the instantaneous failure of the samples well. The actual yield levels corresponding to the peak instantaneous elastic modulus of the samples linearly decreased with increasing graded loading rate. The functional relationship between the graded loading rate and the elastic modulus hardening coefficient, the actual yield stress, and the strain rate decay coefficient were established, which could quantitatively describe the influence of different graded loading rates on the creep and hardening characteristics of anthracite and predict its creep damage. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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17 pages, 13027 KiB  

Open AccessArticle

Experimental Study on the Reciprocating Shear Characteristics and Strength Deterioration of Argillaceous Siltstone Rockfill Materials

by Jun Du, Dong Li, Zhiming Xiong, Xinggang Shen, Chenchen Li and Weiwei Zhu

Appl. Sci. 2023, 13(15), 8888; https://doi.org/10.3390/app13158888 - 2 Aug 2023

Viewed by 913

Abstract

The reciprocating shear mechanical properties and strength deterioration mechanisms of rockfill materials are of great research significance for high-fill slope stability analysis. To study the shear strength characteristics of argillaceous siltstone rockfill materials with different fabric characteristics under reciprocating shear loading, we analyzed [...] Read more.

The reciprocating shear mechanical properties and strength deterioration mechanisms of rockfill materials are of great research significance for high-fill slope stability analysis. To study the shear strength characteristics of argillaceous siltstone rockfill materials with different fabric characteristics under reciprocating shear loading, we analyzed the shear strength, hysteresis loop area, damping ratio, shear strength parameter, and shear stiffness of coarse-grained soils with different coarse grain contents using a coarse-grained soil direct shear testing machine capable of reciprocating shear and revealed their strength deterioration mechanism. The test results show that the shear strength of argillaceous siltstone rockfill materials is significantly affected by the coarse grain content and the number of reciprocating shears. Specifically, the shear strength increases with the coarse grain content and decreases with the number of reciprocating shears. The hysteresis loop area is positively correlated with the coarse grain content and negatively correlated with the number of reciprocating shears. The damping ratio is not related to the coarse grain content but tends to decrease with the number of reciprocating shears. Soil cohesion and the internal friction angle increase with the coarse grain content and decrease with the number of reciprocating shears. The soil failure shear stiffness is linearly correlated with the coarse grain content, and the normalized shear stiffness is logarithmically related to the number of reciprocating shears. According to these relationships, an empirical formula for the shear stiffness of argillaceous siltstone rockfill materials under different coarse grain contents and different numbers of reciprocating shears can be established to provide a basis for analyzing rockfill stability. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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19 pages, 6964 KiB  

Open AccessArticle

Study on the Deformation and Failure Characteristics of the Long Composite Insulated Cold Transmission Pipe in Deep Mines

by Wenlong Wang, Fengtian Yue, Jingsheng Wei, Tao Gao and Yanjun Qi

Appl. Sci. 2023, 13(15), 8805; https://doi.org/10.3390/app13158805 - 30 Jul 2023

Viewed by 1003

Abstract

To address the delamination and water leakage caused by the fracture of insulated chilled water pipeline (ICWP) in the process of long-distance drilling through deep strata, a new insulated cold transmission pipe with a composite structure was designed based on the actual project. [...] Read more.

To address the delamination and water leakage caused by the fracture of insulated chilled water pipeline (ICWP) in the process of long-distance drilling through deep strata, a new insulated cold transmission pipe with a composite structure was designed based on the actual project. The mechanical and deformation characteristics of the mortar materials of the different filling layers were investigated using uniaxial compression and Brazilian split tests. The distribution law of the maximum principal strain field on the surface during the test process was obtained by applying the digital image correlation method. Based on the experimental results, the finite-difference model was established and FLAC3D was used to analyze the stability of the long-distance composite structure ICWP under different stress conditions. The numerical results show that when the ground stress exceeds 12 MPa, the plastic damage occurs in the inner and outer filling layers of the ICWP. When the ground stress reaches 17.5 MPa, there is a small plastic zone in the cold transmission pipe, but the composite structure ICWP does not affect the regular operation of the pipe. Based on that, the mapping relationship for the plastic damage rate of the inner and outer filling mortar of the ICWP to the ground stress and the parameters of the insulation pipe was constructed to provide a theoretical basis for improving the deformation damage resistance characteristics of the composite structure ICWP. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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12 pages, 2609 KiB  

Open AccessArticle

Study on the Creep of Damage-Containing Anthracite: Theory and Experiment

by Gang Li, Guochao Yan, Shaoqi Kong, Xuyang Bai, Chaofei Du, Jiajun Li and Jiawei Zhang

Appl. Sci. 2023, 13(15), 8691; https://doi.org/10.3390/app13158691 - 27 Jul 2023

Viewed by 1023

Abstract

Fractal derivatives characterize the accelerated creep phase of the creep process. In this study, based on the fractal order theory, the integer-order derivatives are defined from the spatio-temporal self-similarity phenomenon of the dynamic process using the scale change method, and the viscoplastic model [...] Read more.

Fractal derivatives characterize the accelerated creep phase of the creep process. In this study, based on the fractal order theory, the integer-order derivatives are defined from the spatio-temporal self-similarity phenomenon of the dynamic process using the scale change method, and the viscoplastic model is improved to establish a new creep instantonal model with damage to describe the complete creep phase of anthracite. The effects of damage variables on initial and accelerated creep were investigated by performing graded-loading creep tests. Based on the experimental data, inversions of the model-related parameters were performed, and parameter sensitivities were analyzed. The results show that the proposed model can better characterize the complete creep process of anthracite coal, which verifies the correctness and rationality of the model. The damage content affects the initial and accelerated creep strain under different loading levels, and a specific functional relationship exists between them. The study’s findings can provide some reference material for the stability control of anthracite affected by disturbing stresses. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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22 pages, 8240 KiB  

Open AccessArticle

Study on the Mechanism and Prevention of Frequent Mine Seismic Events in Goaf Mining under a Multi-Layer Thick Hard Roof: A Case Study

by Bo Wang, Guorui Feng, Zhongxiang Gao, Junpeng Ma, Sitao Zhu, Jinwen Bai, Zhu Li and Wenda Wu

Minerals 2023, 13(7), 852; https://doi.org/10.3390/min13070852 - 23 Jun 2023

Cited by 1 | Viewed by 1310

Abstract

Mine seismic events are an inevitable dynamic phenomenon occurring in deep mines. A scientific and rational method is needed to evaluate and understand mine seismicity and its induced disasters. In the Ordos mining area of North China, multiple groups of thick hard-bedded sandstone [...] Read more.

Mine seismic events are an inevitable dynamic phenomenon occurring in deep mines. A scientific and rational method is needed to evaluate and understand mine seismicity and its induced disasters. In the Ordos mining area of North China, multiple groups of thick hard-bedded sandstone formations commonly exist in the overlying strata of Jurassic coal seams. In recent years, frequent mine seismic events in many large mines of Ordos have resulted in suspended or limited production, which seriously threatens the safe and efficient operation of 10-million-ton modern mines in China. Therefore, taking the frequent occurrence of mine seismic events in the mining process of goaf working face with a multi-layer thick hard roof in Ordos mine as the research background, this study investigated the mechanism and prevention of mine seismic in goaf working face with the methods of case study, theoretical analysis and field monitoring. The following conclusions are made: when the goaf working face is mined, an “advanced and lateral” L-form roof forms under the coupled influence of the lateral suspension plate formed above the upper working face and the roof of the working face. Due to the common influence from “advanced and lateral” L-form roof activation, the gradually breaking multi-layer thick hard roof, thick hard roof group bending and prying effects, in addition to excessively fast or uneven mining speed, mine seismic events will occur frequently when the exceedance warning index (EWI) is breeched. On this basis, coordinated blasting to break the roof along two roadways and within the working face is put forward as a measure with the purpose of preventing and controlling mine seismic events, and a robust effect on mine seismic reduction and disaster prevention is obtained in field application. The research results can serve as a reference for the development and application of mine seismic mechanism and blasting vibration reduction technology on the working face where there is a multi-layer thick hard roof, thereby supporting a strategy of promoting the resource development and energy security of deep mines. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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17 pages, 4990 KiB  

Open AccessArticle

Numerical Simulation and Analysis of the Causes and Distribution of Secondary Lining Cracks in Overlapping Railway Tunnels

by Qianwei Xu, Jinli Xie, Feng Zhou and Zhuohua Tang

Appl. Sci. 2023, 13(11), 6436; https://doi.org/10.3390/app13116436 - 25 May 2023

Cited by 2 | Viewed by 1412

Abstract

The construction of new tunnels above existing tunnels has become increasingly common to optimize underground space utilization. However, such construction may pose potential engineering hazards due to cracking in the secondary lining of the lower tunnel. This study investigates the occurrence and evolutionary [...] Read more.

The construction of new tunnels above existing tunnels has become increasingly common to optimize underground space utilization. However, such construction may pose potential engineering hazards due to cracking in the secondary lining of the lower tunnel. This study investigates the occurrence and evolutionary characteristics of longitudinal cracks in the secondary lining of the lower tunnel during the construction of the upper tunnel adjacent to the pre-existing lower tunnel. Our findings demonstrate that the construction of the upper tunnel has a significant impact on the lower tunnel, as confirmed by on-site monitoring and numerical simulation results. The redistribution of surrounding rock pressure alters the stress distribution of the secondary lining of the lower tunnel, which is the primary reason for the observed cracking. To mitigate the risk of cracks, two different methods are recommended based on the density of the cracks. In areas with less dense cracks, the method of chiseling and grouting is adopted to improve the strength of the secondary lining, while in relatively dense areas, resin anchor rods with saddle joints are used to enhance the stability of the surrounding rock. Long-term monitoring, classification, and early warning of cracks are also recommended. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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21 pages, 15612 KiB  

Open AccessArticle

Stability Study of the Roof Plate of the Yuanjue Cave Based on the Equivalent Support Stiffness Method

by Yongli Hou, Jiabing Zhang, Bin Li, Yifei Gong, Yingze Xu, Meng Wang and Chun Zhu

Appl. Sci. 2023, 13(7), 4451; https://doi.org/10.3390/app13074451 - 31 Mar 2023

Cited by 1 | Viewed by 1711

Abstract

As precious cultural heritage sites, the state of preservation of cave temples is closely related to the geological and climatic conditions in which they are located. This paper constructed an analytical method of sized slate stability based on the equivalent support stiffness method. [...] Read more.

As precious cultural heritage sites, the state of preservation of cave temples is closely related to the geological and climatic conditions in which they are located. This paper constructed an analytical method of sized slate stability based on the equivalent support stiffness method. The stability analysis of the roof slab of Yuanjue Cave was carried out by establishing a three-dimensional numerical calculation model. Through comparative analysis of the results of stress and displacement fields under different conditions, the stress and deformation characteristics of the roof slab of Yuanjue Cave were revealed, as well as the study of the main factors affecting the stability of the roof slab of Yuanjue Cave and the key slate to be monitored. The main research results are as follows. The stress deformation of the roof plate of Yuanjue cave is mainly divided into the initial uniform change stage, the medium-term stable change stage or the medium-term accelerated change stage, and the later rapid change stage. With the increase in the number of overhanging and broken slates and the increase in the damage factor of cracked slates, the vertical stress extremum of the stones increases continuously, and the equivalent support stiffness decreases, which aggravates the uneven stress deformation of the roof of the Yuanjue Cave. This study provides a reliable reference basis for the stability analysis and evaluation of the roof slab of a large number of cave temples existing in the Sichuan and Chongqing areas in China. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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16 pages, 7113 KiB  

Open AccessArticle

A Coupled Darcy-Forchheimer Flow Model in Fractured Porous Media

by Feng Xiong, Yijun Jiang, Chun Zhu, Lin Teng, Hao Cheng and Yajun Wang

Appl. Sci. 2023, 13(1), 344; https://doi.org/10.3390/app13010344 - 27 Dec 2022

Cited by 2 | Viewed by 1684

Abstract

Aiming at nonlinear flow in fractured porous media, based on the finite volume method, the discrete equations of Darcy flow in porous and Forchheimer flow in fracture were derived, and a solution method for coupling flow is proposed. The flow solution by the [...] Read more.

Aiming at nonlinear flow in fractured porous media, based on the finite volume method, the discrete equations of Darcy flow in porous and Forchheimer flow in fracture were derived, and a solution method for coupling flow is proposed. The flow solution by the proposed method for single fracture and intersecting fracture is verified against Frih’s solution. Based on this method, nonlinear flow behavior for fractured rock deep-buried tunnels under high water heads was discussed. The results show that the hydraulic gradient of surrounding rock is characterized by “large at the bottom and small at the top”, with a maximum difference of 2.5 times. Therefore, the flow rate at the bottom of the tunnel is greater than that at the top. The fracture flow rate along the flow direction is also greater than that in the vertical flow direction, with a maximum difference of 60 times. The distribution homogeneity and density of fracture are the most important factors that affect the hydraulic behavior of fractured rock tunnels. The more fractures concentrated in the direction of water pressure and the greater the density, the greater the surrounding rock conductivity and the greater the flow rate of the tunnel. Under this condition, the water-inflow accident of the tunnel would be prone to occur. The research results provide a reference for the waterproof design and engineering practice of fractured rock tunnels. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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22 pages, 6843 KiB  

Open AccessArticle

Study on Dynamic Disaster Mechanisms of Thick Hard Roof Induced by Hydraulic Fracturing in Surface Vertical Well

by Xiaoguang Shang, Sitao Zhu, Fuxing Jiang, Jinhai Liu, Jiajie Li, Michael Hitch, Hongliang Liu, Shibin Tang and Chun Zhu

Minerals 2022, 12(12), 1537; https://doi.org/10.3390/min12121537 - 29 Nov 2022

Cited by 7 | Viewed by 1578

Abstract

With the increase in mining depth and the deterioration of mining conditions, thick and hard overburden movement frequently induces mine earthquakes and rock bursts. Some mines are expected to prevent and control super thick hard rock mine earthquakes through vertical ground well water [...] Read more.

With the increase in mining depth and the deterioration of mining conditions, thick and hard overburden movement frequently induces mine earthquakes and rock bursts. Some mines are expected to prevent and control super thick hard rock mine earthquakes through vertical ground well water fracturing technology. However, the dynamic underground disaster appears more intense. Taking the ‘11.30’ mine earthquake in a mine in Shandong Province as the engineering background, the dynamic disaster mechanism of an extraordinarily thick and hard roof induced by hydraulic fracturing of vertical wells on the ground was studied utilizing field investigation, accident case analysis, similar material simulation test, and theoretical analysis. The main conclusions are as follows: (1) After hydraulic fracturing vertical wells on the ground, the movement mode of thick and hard roofs changed from layer-by-layer to overall sliding movement; (2) The influence range of the advanced abutment pressure of the working face is reduced by the hydraulic fracturing of the vertical shaft, and the peak value of the advanced abutment pressure increases. Furthermore, the advanced abutment pressure’s peak is far from the coal wall; (3) The hydraulic fracturing technology of cross-arranged vertical surface deep and shallow wells and the hydraulic fracturing technology of cross-perforated surface multi-branch horizontal wells are proposed to avoid the dynamic disaster of overall sliding movement of an extremely thick hard roof induced by surface hydraulic fracturing. Therefore, these research results provide significance for preventing and controlling mine earthquakes and rock bursts in super thick hard roof mines. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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19 pages, 7890 KiB  

Open AccessArticle

Heat Transfer and Flow Characteristics of Coal Slurries under the Temperature Difference between Inside and Outside of the Channel

by Yang Liu, Xintao Hu, Feng Gao and Yanan Gao

Appl. Sci. 2022, 12(23), 12028; https://doi.org/10.3390/app122312028 - 24 Nov 2022

Viewed by 1280

Abstract

The pipeline transportation of coal slurries is always subject to a temperature difference between the outdoors environment and the fluid body. As slurries’ viscosity is typically temperature dependent, the flow is accompanied by the heat transfer. In this study, we used the CFD [...] Read more.

The pipeline transportation of coal slurries is always subject to a temperature difference between the outdoors environment and the fluid body. As slurries’ viscosity is typically temperature dependent, the flow is accompanied by the heat transfer. In this study, we used the CFD method to investigate temperature distributions and flow structures in straight and curved channels, which has not previously been investigated, according to our knowledge. First, the results demonstrate that the cooling process influences the flow structures along the stream. The fluid turns more sharply in the cooler fluid in the curved channel, the streamlines overlap at an earlier position within the bend, and the velocity maximum zone is wider. Cooling also has a significant impact on transverse flow. Because of the higher viscosity of the more cooled fluid and thus the difficulty of shearing the fluid in the stream-wise direction, the vorticity and strength of the vortex flow are greater. The fluid velocity at the central part of the channel points toward the inner wall at the beginning of the bend, resulting in an inner-wall biased temperature distribution, as the heat transfer is partially carried out by the fluid velocity. The central velocity points toward the outer wall at the end of the bend, resulting in the outer-wall biased temperature profile. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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11 pages, 2554 KiB  

Open AccessCommunication

A Potential Mechanism of the Satellite Thermal Infrared Seismic Anomaly Based on Change in Temperature Caused by Stress Variation: Theoretical, Experimental and Field Investigations

by Peixun Liu, Shunyun Chen, Qiongying Liu, Yanshuang Guo, Yaqiong Ren, Yanqun Zhuo and Jiahui Feng

Remote Sens. 2022, 14(22), 5697; https://doi.org/10.3390/rs14225697 - 11 Nov 2022

Cited by 7 | Viewed by 1570

Abstract

Satellite thermal infrared remote sensing has received worldwide attention in earthquake-precursors exploration. Meanwhile, it has also encountered great controversy due to the lack of quantitative interpretation of the observations, despite the existing qualitative physical mechanisms being able to greatly help us understand thermal [...] Read more.

Satellite thermal infrared remote sensing has received worldwide attention in earthquake-precursors exploration. Meanwhile, it has also encountered great controversy due to the lack of quantitative interpretation of the observations, despite the existing qualitative physical mechanisms being able to greatly help us understand thermal infrared anomalies. Here, we report a potential mechanism to quantitatively analyze co-seismic thermal infrared anomalies based on temperature change caused by stress variation through theoretical, experimental, and field investigations. This paper firstly deduces theoretically the temperature variation during elastic deformation of rock on the basis of the thermodynamic theory. Secondly, three laboratory experiments on rock samples are conducted to verify the theoretical estimates of the temperature changes caused by stress variations using an infrared camera with the spectral range of 8~12 μm. Thirdly, a mechanical model on thrust faults is built to evaluate the co-seismic temperature drop as a result of thrust faulting. The model shows that the co-seismic temperature drop in rocks should be in the order of 0.18 K. This variation in rock temperature may cause a change in heat equivalent to changes in shallow atmospheric temperatures of 3.0–6.0 K, which is in accordance with the temperature anomalies observed by satellite thermal infrared remote sensing. In addition, the temperature change caused by crustal stress variation may involve a large spatial scale, covering the whole focal area, which has characteristics of regional distribution and is conducive to satellite observation. Therefore, a quantitative explanation of the satellite thermal infrared seismic anomaly mechanism can be given via the temperature change caused by crustal stress variation. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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16 pages, 5117 KiB  

Open AccessArticle

Numerical Simulation Analysis Method of the Surrounding Rock and Support Bearing Capacity in Underground Cavern

by Ming Xiao, Junqing Ren, Binxin Zhao, Chen Chen and Shijie Chen

Energies 2022, 15(20), 7788; https://doi.org/10.3390/en15207788 - 20 Oct 2022

Cited by 1 | Viewed by 1406

Abstract

After the excavation of an underground cavern, how the surrounding rock and the support work together to bear the excavation load is an important prerequisite to correctly analyze the joint force characteristics; effectively play the role of support; and ensure the safety, efficiency, [...] Read more.

After the excavation of an underground cavern, how the surrounding rock and the support work together to bear the excavation load is an important prerequisite to correctly analyze the joint force characteristics; effectively play the role of support; and ensure the safety, efficiency, and economy of underground cavern construction. Starting from the elastic-plastic load release characteristics of surrounding rock, this paper proposes a calculation method of the elastic load coefficient of surrounding rock and a graded release method of plastic load, which ensures the actual effect of the synergistic action of the first support and surrounding rock. Based on the elastic-plastic damage evolution characteristics of surrounding rock, a weighted iterative calculation method of elastic-plastic damage is proposed, and an evaluation method of load release ultimate bearing capacity of surrounding rock is determined. By monitoring the change law of rock acoustic wave velocity with surrounding rock damage, the relationship between the wave velocity and the damage coefficient of the surrounding rock in the excavation process is deduced, and it is proposed to determine the latest support time for first support by using the measured rock damage wave velocity. Through the numerical simulation analysis of a diversion tunnel excavation and support, the damage evolution law of the surrounding rock with the release of the excavation load is studied. The ultimate bearing capacity of various surrounding rocks and supporting opportunity is determined. The results demonstrate the validity and practicality of the analysis and calculation methods in this paper, which provide a new idea and analysis method for quantifying the bearing capacity of surrounding rock and determining the support timing in the excavation and support design of underground caverns. Full article

(This article belongs to the Topic Complex Rock Mechanics Problems and Solutions)

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