Advances in Fracture Mechanics for Structural Integrity Assessment

A special issue of Machines (ISSN 2075-1702).

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 12456

Special Issue Editors


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Guest Editor

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Guest Editor
Department of Building Engineering, Hunan Institute of Engineering, XiangTan, Hunan 411104, China
Interests: mechanical rock breakage mechanism; novel cutter design for rock excavation storage

Special Issue Information

Dear Colleagues,

Rock fracture behaviors are critical to the structural integrity assessment of geotechnical engineering. Additionally, the understanding of the rock fracture mechanism can accelerate the development of rock excavation machines, including tunnel boring machines (TBM), roadheaders, etc. The recent challenging topics in rock fracture mechanics include the crack distribution, initiation and propagation mechanism, and the fracture responses to high hydraulic pressures. Recently, experimental, numerical, and theoretical studies have been widely applied to probe the rock fracture mechanism. However, the complicated geological conditions may prevent researchers from a comprehensive understanding of the rock fracture process and further result in operation problems of excavation machines. Thus, further studies on rock fracture mechanisms, including the crack initiation and propagation analysis under hydraulic pressure and the assessment method of rock fracture, are essential.

This Special Issue aims to collect original papers, mainly focusing on rock fracture behaviors and the improvement of excavation machines. We welcome theoretical, laboratory, numerical, and field studies.

Subject Areas

  • Fracture initiation and propagation analysis of rocks under hydraulic pressure
  • Mechanical and cracking behaviors of rocks
  • Fracture and failure modeling of rocks under hydraulic pressure
  • Laboratory and theoretical analysis of rock structure fractures
  • Deformation and damage fracture mechanism in rocks
  • Assessment method for rock fracture behaviors
  • Fracture behavior of rocks in stressed environments
  • Rheological fracture behavior of rocks
  • Optimal configurations for excavation machines based on rock fractures
  • Rock breakages by improved rock excavation machines

Prof. Dr. Yanlin Zhao
Prof. Dr. Hang Lin
Prof. Dr. Yixian Wang
Prof. Dr. Jie Liu
Guest Editors

Manuscript Submission Information

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Published Papers (6 papers)

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Research

16 pages, 4096 KiB  
Article
Test Study of Seepage Characteristics of Coal Rock under Various Thermal, Hydraulic, and Mechanical Conditions
by Yanlin Zhao, Qiang Liu, Liming Tang, Jian Liao, Le Chang, Xiaguang Wang, Yang Li and Sheng Ren
Machines 2022, 10(11), 1012; https://doi.org/10.3390/machines10111012 - 2 Nov 2022
Cited by 3 | Viewed by 1303
Abstract
The seepage characteristics of rocks under conditions of multi-field activity have always been important in the field of rock mechanics. This study used the MTS815 multi-functional electro-hydraulic servo rock testing machine to conduct seepage tests on long-flame coal specimens under different confining pressures, [...] Read more.
The seepage characteristics of rocks under conditions of multi-field activity have always been important in the field of rock mechanics. This study used the MTS815 multi-functional electro-hydraulic servo rock testing machine to conduct seepage tests on long-flame coal specimens under different confining pressures, water pressures, and temperatures. This paper presents and discusses the seepage characteristics of coal specimens under the action of thermal hydraulic mechanical multi-field combinations. Considering parameters such as volumetric strain, temperature, thermal expansion coefficient, and initial porosity, the relationships of each parameter with porosity were obtained. The test results revealed that the volumetric strain of coal specimens increased gradually with the increase of temperature. The dynamic viscosity of water decreased with the increase of temperature, which accelerated the movement and circulation of water molecules. The increase in temperature caused the volume of the coal specimen to expand, the pores in the coal specimen squeezed against each other, the pore volume decreased, and the size of the seepage channel slowly decreased, which inhibited the seepage process. Furthermore, permeability gradually decreased with the increase of temperature. This inhibited the occurrence of seepage, and the higher the confining pressure, the lower was the permeability. The porosity of coal specimens decreased with the increase in temperature, which had an inhibitory effect on the seepage behavior. The results of this study provide experimental and theoretical support for the safe mining of coal and rock in underground mines. Full article
(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)
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11 pages, 2571 KiB  
Article
Ultimate Bearing Capacity of Bottom Sealing Concrete in Underwater Deep Foundation Pit: Theoretical Calculation and Numerical Analysis
by Shuo Chen, Yonghai Li, Panpan Guo, Xiaohan Zuo, Yan Liu, Haiping Yuan and Yixian Wang
Machines 2022, 10(10), 830; https://doi.org/10.3390/machines10100830 - 21 Sep 2022
Cited by 1 | Viewed by 1378
Abstract
The cofferdam method is generally applied in the construction of underwater pier foundation in bridge engineering, and the pouring of bottom sealing concrete is one of the important links in the construction of the cofferdam. The bottom sealing concrete can prevent water seepage [...] Read more.
The cofferdam method is generally applied in the construction of underwater pier foundation in bridge engineering, and the pouring of bottom sealing concrete is one of the important links in the construction of the cofferdam. The bottom sealing concrete can prevent water seepage and balance the main body of the cofferdam, and its structural size and construction quality have a great influence on the above functions. Under the condition of large water level difference, it is difficult to determine the reasonable thickness of the bottom sealing concrete. There are few related studies in this field, and there is a lack of systematic summary of calculation theory. This work theoretically deduces the approximate solution of ultimate bending moment and ultimate stress of the bottom sealing concrete, introduces two different calculation methods, systematically summarizes the calculation methods of three kinds of ultimate stress, analyzes the calculation methods of ultimate bonding force, and uses ANSYS finite element software to simulate a specific bottom sealing concrete model, and compares it with the theoretical calculation results. The maximum stress obtained by the approximate solution is closer to the actual monitoring data than the traditional method, and the calculation method of the bonding force can be used to make a rough estimate. Full article
(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)
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20 pages, 10610 KiB  
Article
Shear Failure Mechanism and Numerical Simulation Analysis of Rock-like Materials with an Embedded Flaw
by Mingyang Teng, Jiashen Li, Shuailong Lian, Jing Bi and Chaolin Wang
Machines 2022, 10(5), 382; https://doi.org/10.3390/machines10050382 - 16 May 2022
Cited by 1 | Viewed by 1888
Abstract
In this study, the failure characteristics of self-made rock with internal flaws under shear were studied and a numerical simulation analysis was carried out. Firstly, based on basic physical and mechanical tests, the shear strength characteristics of rocks with built-in 3D defects were [...] Read more.
In this study, the failure characteristics of self-made rock with internal flaws under shear were studied and a numerical simulation analysis was carried out. Firstly, based on basic physical and mechanical tests, the shear strength characteristics of rocks with built-in 3D defects were summarized. PFC3D simulation software was used to model the samples with flaws, and the microscopic parameters were calibrated according to the test results. From the simulation results, it was found that the generation mode of microcracks from the flaw tip was different. The microcracks of forward shear and reverse shear were mainly generated from the horizontal direction, while the microcracks of lateral shear gradually increased from the upper and lower ends of the flaw in the opposite direction. When the peak shear strength was reached, the total number of cracks was the largest in lateral shear and the smallest in forward shear. When studying the particle velocity vector field, it was found that when reaching the peak shear strength, the particles on both sides of the prefabricated flaw appeared to be in vortex motion. When α = 45° and σn = 2 MPa, the failure mode of forward shear and lateral shear was shear-tensile-shear (S-T-S), and that of reverse shear and the intact specimen was shear-shear-shear (S-S-S). The lateral shear tensile effect was the most obvious and was mainly concentrated in the middle part of the sample. Full article
(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)
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25 pages, 6493 KiB  
Article
Numerical Investigation of Influence of Fluid Rate, Fluid Viscosity, Perforation Angle and NF on HF Re-Orientation in Heterogeneous Rocks Using UDEC T-W Method
by Shuai Zhang, Jinhai Xu, Liang Chen, Mingwei Zhang, Takashi Sasaoka, Hideki Shimada and Haiyang He
Machines 2022, 10(2), 152; https://doi.org/10.3390/machines10020152 - 18 Feb 2022
Cited by 1 | Viewed by 1584
Abstract
Numerical simulation is very useful for understanding the hydraulic fracture (HF) re-orientation mechanism from artificial weaknesses. In this paper, the UDEC T-W (Trigon–Weibull distribution) modeling method is adopted to simulate the hydraulic fracturing process in heterogeneous rocks. First, the reliability of this method [...] Read more.
Numerical simulation is very useful for understanding the hydraulic fracture (HF) re-orientation mechanism from artificial weaknesses. In this paper, the UDEC T-W (Trigon–Weibull distribution) modeling method is adopted to simulate the hydraulic fracturing process in heterogeneous rocks. First, the reliability of this method is validated against previous laboratory experiments and numerical simulations. Then the effects of fluid rate, fluid viscosity, perforation angle and natural fracture (NF) on the HF re-orientation process in heterogeneous rocks are studied independently. The results show that the HF re-orientation process depends on the combined effect of these factors. The HF re-orientation distance increases significantly, the final HF re-orientation trajectory becomes more complex and the guiding effect of perforation on the HF propagation path is more evident with the increase of fluid rate, fluid viscosity, and perforation angle if the hydraulic fracturing is performed in relatively heterogeneous rocks, while the differential stress is the main influencing factor and is more likely to dictate the HF propagation path if the rocks become relatively homogeneous. However, increasing the fluid viscosity and fluid rate can attenuate the impact of differential stress and can promote HF propagation along the perforation direction. Besides, NFs are also the important factor affecting HF re-orientation and induce secondary HF re-orientation in some cases in heterogeneous rocks. Full article
(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)
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16 pages, 7504 KiB  
Article
Role of Cyclic Thermal Shocks on the Physical and Mechanical Responses of White Marble
by Yujie Feng, Haijian Su, Yinjiang Nie and Honghui Zhao
Machines 2022, 10(1), 58; https://doi.org/10.3390/machines10010058 - 13 Jan 2022
Cited by 5 | Viewed by 1734
Abstract
Marble is a common rock used in many buildings for structural or ornamental purposes and is widely distributed in underground engineering projects. The rocks are exposed to high temperatures when a tunnel fire occurs, and they will be rapidly cooled during the rescue [...] Read more.
Marble is a common rock used in many buildings for structural or ornamental purposes and is widely distributed in underground engineering projects. The rocks are exposed to high temperatures when a tunnel fire occurs, and they will be rapidly cooled during the rescue process, which has a great impact on the rock performance and the underground engineering stability. Therefore, the role of cyclic thermal shocks on the physical and mechanical properties of marble specimens was systematically investigated. Different cyclic thermal shock treatments (T = 25, 200, 400, 600, 800 °C; N = 1, 3, 5, 7, 9) were applied to marble specimens and the changes in mass, volume, density and P-wave velocity were recorded in turn. Then, the thermal conductivity, optical microscopy and uniaxial compression tests were carried out. The results showed that both the cyclic thermal shock numbers (N) and the temperature level (T) weaken the rock properties. When the temperature of a thermal shock exceeds 600 °C, the mass loss coefficient and porosity of the marble will increase significantly. The most noticeable change in P-wave velocity occurs between 200 and 400 °C, with a 52.98% attenuation. After three thermal shocks, the cyclic thermal shock numbers have little influence on the uniaxial compressive strength and Young’s modulus of marble specimens. Shear failure is the principal failure mode in marble specimens that have experienced severe thermal damage (high N or T). The optical microscopic pictures are beneficial for illustrating the thermal cracking mechanism of marble specimens after cyclic thermal shocks. Full article
(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)
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20 pages, 6676 KiB  
Article
Investigation of the Shear Mechanical Behavior of Sandstone with Unloading Normal Stress after Freezing–Thawing Cycles
by Shuailong Lian, Jiashen Li, Fei Gan, Jing Bi, Chaolin Wang and Kun Zheng
Machines 2021, 9(12), 339; https://doi.org/10.3390/machines9120339 - 8 Dec 2021
Cited by 5 | Viewed by 2525
Abstract
Freezing–thawing action has a great impact on the physical and mechanical deterioration processes of rock materials in cold areas where environmental changes are very complicated. The direct shear test under unloading normal stress was adopted to investigate the shear mechanical behavior of sandstone [...] Read more.
Freezing–thawing action has a great impact on the physical and mechanical deterioration processes of rock materials in cold areas where environmental changes are very complicated. The direct shear test under unloading normal stress was adopted to investigate the shear mechanical behavior of sandstone samples after a freezing–thawing cycle in this paper. The failure shear displacement (Dsf), the failure normal displacement (Dnf), the shear displacement of unloading (Dsu), and the normal displacement of unloading (Dnu) were analyzed to describe the evolution of shear and normal deformation during the test. The results indicated that the shear displacement increased as the freezing–thawing cycle duration increased in a direct shear test under unloading normal stress. The unloading rate and the number of freezing–thawing cycles affected the failure pattern of the rock sample significantly in both the direct shear test under unloading normal stress and the direct shear test. The three-dimensional inclination angle, the distortion coefficient, and the roughness correlation coefficient of the fracture surface are dependent on the number of freezing–thawing cycles and the unloading rate. The surface average gradient mode of the fracture surface decreased as the freezing–thawing cycle times and unloading rate rose. Full article
(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)
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