Constant Axial Stress Research Articles

Energy characteristics of saturated Jurassic sandstone in western China under different stress paths

AbstractTo study the energy evolution and failure characteristics of saturated sandstone under unloading conditions, rock unloading tests under different stress paths were conducted. The energy evolution mechanism of the unloading failure of saturated sandstone was systematically explored from the perspectives of the stress path, the initial confining pressure, and the energy conversion rate. The results show that (1) before the peak stress, the elastic energy increases with an increase in deviatoric stress, while the dissipated energy slowly increases first. After the peak stress, the elastic energy decreases with the decrease of deviatoric stress, and the dissipated energy suddenly increases. The energy release intensity during rock failure is positively correlated with the axial stress. (2) When the initial confining pressure is below a certain threshold, the stress path is the main factor influencing the total energy difference. When the axial stress remains constant and the confining pressure is unloading, the total energy is more sensitive to changes in the confining pressure. When the axial stress remains constant, the compressive deformation ability of the rock cannot be significantly improved by the increase in the initial confining pressure. The initial confining pressure is positively correlated with the rock's energy storage limit. (3) The initial confining pressure increases the energy conversion rate of the rock; the initial confining pressure is positively correlated with the energy conversion rate; and the energy conversion rate has a high confining pressure effect. The increase in the axial stress has a much greater impact on the elastic energy than the confining pressure. (4) When the deviatoric stress is small, the confining pressure mainly plays a protective role. Compared with the case of triaxial compression paths, the rock damage is more severe under unloading paths, and compared with the case of constant axial stress, the rock damage is more severe under increasing axial stress.

Bending fatigue performance of high-strength seven-wire monostrand

Large-amplitude cable vibrations are remarkably common in cable-stayed bridges subjected to wind and mechanical loading due to low inherent damping of these structures. Although the high slenderness ratio of cables means that bending moments are not normally significant over their free length, local effects near the cable anchorage induce non-negligible bending stress variation under dynamic loading, which could lead to fatigue failure of stay cables. In modern parallel strand stay cables, the fatigue performance depends on the fatigue properties of the individual seven-wire monostrands which together make up the cable. We introduce a new bending fatigue testing device for seven-wire monostrand which can control the fatigue loading in the axial and transverse directions of the cable independently. The fatigue endurance of monostrand with guide deviators is significantly longer than without guide deviators present, especially for smaller bending fatigue amplitudes. We found that bending fatigue life of monostrand is also reduced by increased constant or dynamic axial stress, but over-tensioning of the monostrand (e.g. during construction) had no consistently adverse effect on fatigue life. For monostrand loaded in severe bending, fatigue occurs due to the bending stress variation caused by the combination of bending moments and axial forces at the extreme edges of the monostrand cross-section, rather than due to relative movement and fretting between adjacent wires within the monostrand.

Moment-less arches of constant axial stress: Implications for design

The work discusses key features and advantages of optimal 2-pin arches shaped by statistically prevalent (permanent) load and a constant value of axial stress ensuring a moment-free action. A non-conventional design approach, known as analytical form-finding, is used to shape the arches, with guidance given for both symmetric and asymmetric forms. Previously discovered Design Space/existence of symmetric arches of constant axial stress is extended here to cover asymmetric forms. Minimum values of constant stress to be used in form-finding of constant stress arches made of various materials are given. Ultimate load analysis, using permanent and variable patch loads, show advantages of these structures over other arch forms. The work challenges structural optimisation approaches that assume arches of least weight to be optimal, while, in fact, they offer limited design options and are just a special case of constant stress arches. Conventional design approaches that minimise the weight of a structure, but within an imposed geometric configuration, produce non-optimal structures. By exhibiting a minimal stress response to loading, constant stress arches are analogous to highly optimised objects found in nature; this feature gives them the potential to address sustainability and durability issues facing our future infrastructure.

Durability assessment of GFRP bars exposed to combined accelerated aging in alkaline solution and a constant load

Employing fiber-reinforced polymer (FRP) bars as reinforcement in reinforced concrete (RC) elements is a promising approach to solve the issues associated with steel corrosion in RC elements owing to the high corrosion resistance of FRP bars. Although a number of studies on the durability of glass FRP (GFRP) bars in the alkaline environment are available, most of which ignored the influence of sustained loads. This paper presents an experimental program on tensile tests on GFRP bars made of three distinct matrix resins (i.e. epoxy, vinyl ester and polyester), after exposure to combined alkaline solution immersion, an elevated temperature and a constant load. A novel level device was developed, and a prescriptive constant axial stress was imposed on GFRP bars, and the bars with or without a sustained load were exposed to an alkaline solution and an elevated temperature of 60 °C. The main parameters investigated in the present study included aging times, constant stress levels, exposure conditions and types of resin matrices of the GFRP bars. The residual tensile properties of the GFRP bars were tested and presented. The microscopy method was adopted to check the internal defects in the GFRP bars with or without exposures. Test results show that three months of exposure in alkali and loading could lead to more than 40% strength decreases of the GFRP bars. Compared with GFRP bars after exposure to alkaline solution solely, the presence of the constant tensile load only leads to small further detrimental effect in tensile properties of GFRP bars.

Numerical simulation of mechanical behavior of rock samples under uniaxial and triaxial compression testsy

Purpose. The research aims to investigate how the load influences the ultimate compressive strength of rocks at failure. It uses both a uniaxial compression test, which involves incremental displacements, and a triaxial compression test, which applies varying confining stresses while maintaining a constant axial compression stress and incrementally increasing the displacement. Methods. To conduct the investigation, the researchers used RS2D, a rock-soil software, to examine the impact of different incremental displacements and confining stresses on the strength properties of various rock samples. The numerical analysis includes Fayum argillaceous sand, Sinai coal, Aswan granite, Assiut limestone, and Red-Sea phosphate. Findings. The research findings indicate that the ultimate compressive strength of rocks at failure is achieved with minor incremental displacements. Conversely, an increase in the confining stress leads to higher ultimate tensile strength, deviatoric stresses, and volumetric strain. However, the stress factor decreases in relation to the axial strain percentage. Originality. The simulator adopts Mohr-Coulomb failure criterion, presents and discusses the results in terms of stress-strain (σ-ε) curves, stress ratio (σ1/σ3), deviatoric stresses (σ1-σ3) and volumetric strain with respect to the percentage of axial strain. Practical implications. Using numerical modeling analysis, it becomes possible to reproduce the rock failure mechanisms observed in uniaxial and triaxial compression tests. This methodology has the potential to reduce the need for extensive experimental testing when assessing the tensile strength of rocks under different loads. As a result, both time and costs can be minimized.

Triaxial Deformation of the Goldwyer Gas Shale at In Situ Stress Conditions—Part II: Viscoelastic Creep/Relaxation and Frictional Failure

To understand the geomechanical implications of long-term creep (time-dependent deformation) response of gas shale, short-duration creep was recorded from laboratory triaxial tests on ten Goldwyer gas shale samples in the onshore Canning Basin at in situ stress conditions under constant differential axial stress. A simple power-law function captures primary creep behaviour involving elastic compliance constant B and time-dependent factor n. Experimental creep data revealed larger axial creep strain in clay and organic-rich rocks, than those dominated by carbonates. Anisotropic nature of creep was observed depending upon the direction of constant axial stress application (perpendicular or parallel to the bedding plane). Upon the application of linear viscoelastic theory on laboratory creep fitting coefficients, differential horizontal stress accumulation over a geological time scale was estimated from the viscoelastic stress relaxation concept. Further, this model was used to derive lithology-dependent least principal stress (Shmin) magnitude at depth for two vertical wells intersecting the Goldwyer gas shale formations. This newly proposed Shmin model was found to have a profound influence on designing hydraulic fracture simulation. Further, pore size distribution and specific surface area value SN2 were derived from low-pressure gas adsorption experiments. These physical properties along with weak mineral components were linked with creep constitutive parameters to understand the physical mechanisms of creep. A strong correlation was noted between SN2 and creep parameters n and B. Finally, an attempt was made to investigate how gas shale composition and failure frictional properties can influence shear fracturing.

Influence of joint inclination on mechanical behaviors of shales during unloading-induced slip processes

To investigate the effect of joint inclination on the mechanical behaviors of unloading-induced slip processes, shale samples with different joint inclinations (θ) were tested under constant axial stress and graded unloading of confining pressure to induce slip. The results show that the slip tests resulted in scratches and damage of the rock matrix, thus increasing joint roughness coefficient (JRC) of saw-cut surface samples by values of 4.69, 2.75 and 2.67 for θ = 30°, 40° and 50°, respectively. With the unloading of confining pressure, the samples experienced creep slip, quasi-static slip, and dynamic slip, respectively. The velocity at creep slip, quasi-static slip and dynamic slip decreased with the increase in θ. The average velocities of quasi-static slip are 2.9 × 10−2 mm/s, 1.1 × 10−2 mm/s and 2.1 × 10−3 mm/s for θ = 30°, 40° and 50°, respectively. As the slip progresses, the micro-convexities on the joint are sheared off, resulting in a deterioration of the interlocking effect, which causes the occurrence time of quasi-static slip to advance in an unloading stage and the duration to increase. The friction coefficient (μ) decreased by 2.22%, which changes from 0.45 to 0.44 for the sample with θ = 30°, indicating that the friction strength was slightly weakened during the unloading-induced slip. As θ increases, the friction strength of the sample was enhanced. The μ increased by 19.23% from 0.52 to 0.62 and increased by 28.81% from 0.59 to 0.76 for the sample with θ=40° and 50°, respectively. Based on the experimental results, the unloading-induced slip behaviors were fitted with the rate and state friction law. However, the mechanical behavior of the sample has changed from “shear slip” to “slip failure” as the joint inclination increase, which resulted in the dynamic slip of the sample with θ = 40° and 50° being opposite to the rate weakening described in the rate state friction law.

Influence of exposure in a corrosive environment on ultimate stress of heat-treated welded joints of Al–Mg–Si–Сu alloy

Abstract The priority task of modern aircraft construction is to ensure the reliability of the operation of structures, which depends both on the quality of execution of technological processes during manufacturing and on the corrosion-mechanical durability of welded joints. This work aims to study the influence of contact duration with a corrosive environment on the mechanical strength of the base metal and welded joints of the Al–Mg–Si–Cu alloy, heat-treated in different modes (artificial aging, quenching followed by artificial aging). Corrosion-mechanical tests were carried out under constant axial tensile stress in 3 % NaCl solution for 14 days, followed by determination of the corrosion rate, ultimate strength, and fractographic analysis of the fracture surface. The results showed that the corrosion resistance of the joints is almost equal to the corrosion resistance of the base metal. It was experimentally confirmed that the ultimate strength of the base metal and welded joints decreased after corrosion exposure in a 3 % NaCl solution. This is caused by the embrittlement of the structure and the formation of corrosion defects in the near-surface zone during contact with a corrosive environment, which led to a change like a fracture from ductile to ductile with brittleness.

Creep Behavior of Coal after Cyclic Loading and Unloading and Its Effect on Mining-Induced Stress Boundary

Damage accumulation of coal caused by cyclic loading and creep impacts may ultimately lead to rock failure and dynamic disasters. Quantifying this behavior is crucial for evaluating the mechanical response under creep and cyclic loading processes. Here, creep tests were conducted after cyclic loading and unloading at 10 MPa confining pressure. The elastic modulus and Poisson’s ratio indicated fatigue damage during the entire loading process. The elastic moduli in the unloading stage were slightly higher than those in the loading stage. The gap in Poisson’s ratio decreased in the cyclic loading procedure. The axial and volumetric strains exhibited a slightly negative exponent trend. The stress–strain response indicated hardening and softening effects under constant axial stress. The hardening effect dominated the peak strength at lower axial stresses. The creep-hardening deformation was 0.17 and 0.21 under 88 and 100 MPa, respectively. However, the softening effect played a more significant role at higher applied stresses. Additionally, the peak strength decreased by approximately 2.7 MPa when the axial stress increased from 100 to 102 MPa. The coal near the mining-induced stress boundary experienced cyclic damage, and the creep stress gradually decreased. Thus, the mining-induced stress boundary evolution rate initially increased and was mitigated as the mining-induced stress reduced. Next, the boundary expanded outward and gradually stabilized until the applied loading did not lead to obvious rock failure. Finally, the mining-induced stress boundary in the entire gob may be flat during the long-term evolution. Considering the creep failure time and choosing a suitable time to determine the boundary are essential for preventing dynamic disasters.

Out-of-Plane lateral load capacity of unreinforced masonry walls

ABSTRACT This study tests two full-scale unreinforced masonry (URM) walls under constant axial stress and cyclic out-of-plane lateral loads and proposes mathematical models to predict their rocking and toe crushingstrengths based on the elasticity and plasticity theorems of concrete. The two specimens were designed to simulate a non-perforated URM wall without opening and a URM wall with a door opening. Parallel walls with a length of 590 mm and thickness of 190 mm were constructed at the both ends of the walls in the out-of-plane direction, producing a barbell-shaped section. Test results showed that the URM wall specimens were initially governed by the rocking rotation and then ultimately failed with compressive toe crushing. The value of the equivalent damping coefficient mostly remained constant up to the occurrence of rocking rotation, beyond which it gradually increased. The effect of a door opening on the out-of-plane seismic response of the URM wall was insignificant because the applied lateral loads were resisted mainly by the in-plane action of the auxiliary parallel walls. The proposed models accurately estimated the rocking and toe crushing strengths of URM walls under out-of-plane lateral loads.

Inducing Tensile Failure of Claystone Through Thermal Pressurization in a Novel Triaxial Device

Complex coupled thermo-hydromechanical (THM) loading paths are expected to occur in clay rocks which serve as host formations for geological radioactive waste repositories. Exothermic waste packages heat the rock, causing thermal strains and temperature induced pore pressure build-up. The drifts are designed in such a way as to limit these effects. One has to anticipate failure and fracturing of the material, should pore pressures exceed the tensile resistance of the rock. To characterise the behaviour of the Callovo-Oxfordian claystone (COx) under effective tension and to quantify the tensile failure criterion, a laboratory program is carried out in this work. THM loading paths which correspond to the expected in situ conditions are recreated in the laboratory. To this end, a special triaxial system was developed, which allows the independent control of radial and axial stresses, as well as of pore pressure and temperature of rock specimens. More importantly, the device allows one to maintain axial effective tension on a specimen. Saturated cylindrical claystone specimens were tested in undrained conditions under constrained lateral deformation and under nearly constant axial stress. The specimens were heated until the induced pore pressures created effective tensile stresses and ultimately fractured the material. The failure happened at average axial effective tensile stresses around 3.0 MPa. Fracturing under different lateral total stresses allows one to describe the failure with a Hoek–Brown or Fairhurst’s generalized Griffith criterion. Measured axial extension strains are analysed based on a transversely isotropic thermo-poroelastic constitutive model, which is able to satisfactorily reproduce the observed behaviour.

Investigation of Friction Stir-Welded B4C Particles-Reinforced Copper Joint: Mechanical, Fatigue, and Metallurgical Properties

Solid-state friction stir welding (FSW) is a sophisticated technique that can join materials that are similar and different without significantly affecting the properties of the base materials. The purpose of this study is to enhance the tensile strength, micro-hardness, and fatigue strength of the copper (C1100) butt-joints reinforced with B4C nanoparticles. The effects of B4C nanoparticle inclusion on the mechanical properties of the fabricated joints are studied in correlation with the microstructural features of the welded joints using optical microscopy. The joints are fabricated on a specialized friction stir welding machine (VMC-TC-1200) with a square pin-profiled tool. Defect-free joints of 3 mm copper plates are produced at the constant tool rotational speed of 1100 rpm, welding speed of 30 mm/min, plunge depth of 0.25 mm, and constant axial stress of 5 kN. B4C particles of 1, 2, 3, and 4wt% are added to the joints and their properties are compared with the joints produced without the inclusion of B4C particles to study the effects of the addition of nanoparticles. The joints attained a maximum micro-hardness of 123 HV, fatigue strength of 159 MPa, and tensile strength of 203 MPa with the addition of 3% B4C. Microstructural investigations performed through an optical microscope and scanning electron microscope (SEM) indicated the presence of homogeneously distributed B4C particles engulfed by finely refined grains. The thermal conductivity of the B4C particles facilitated the smooth flow of copper around the particles by forming a thin lubricating layer, thus improving the properties of the joints. Furthermore, this study has established that the addition of B4C particles is an effective and eco-friendly method of producing strong joints which could be used for industrial and defense applications.

Constant stress arches and their design space.

It is generally accepted that an optimal arch has a funicular (moment-less) form and least weight. However, the feature of least weight restricts the design options and raises the question of durability of such structures. This study, building on the analytical form-finding approach presented in Lewis (2016. Proc. R. Soc. A 472, 20160019. (doi:10.1098/rspa.2016.0019)), proposes constant axial stress as a design criterion for smooth, two-pin arches that are moment-less under permanent (statistically prevalent) load. This approach ensures that no part of the structure becomes over-stressed under variable load (wind, snow and/or moving objects), relative to its other parts—a phenomenon observed in natural structures, such as trees, bones, shells. The theory considers a general case of an asymmetric arch, deriving the equation of its centre-line profile, horizontal reactions and varying cross-section area. The analysis of symmetric arches follows, and includes a solution for structures of least weight by supplying an equation for a volume-minimizing, span/rise ratio. The paper proposes a new concept, that of a design space controlled by two non-dimensional input parameters; their theoretical and practical limits define the existence of constant axial stress arches. It is shown that, for stand-alone arches, the design space reduces to a constraint relationship between constant stress and span/rise ratio.

The meso-fracturing mechanism of marble under unloading confining pressure paths and constant axial stress

Failure tests on marble during unloading confining-pressure under constant axial stress and simulations with the particle flow code were performed. The influence mechanism of the unloading rate of the confining pressure, initial unloading stress, and confining pressure on the failure characteristics of, and crack propagation in, marble was studied. By using the trial-and-error method, the conversion relationship between the unloading rates of confining pressures in laboratory tests and numerical simulations was ascertained. Micro-cracks formed in the unloading process of confining pressure are dominated by tension cracks, accompanied by shear cracks. The propagation of shear cracks lags that of tension cracks. As the confining pressure is increased, more cracks occur upon failure of the samples. The proportion of shear cracks increases while that of tension cracks decreases. The failure mode of samples undergoes a transition from shear-dominated failure to conjugated shear failure.

Experimental investigation on the permeability and damage characteristics of raw coal under tiered cyclic unloading and loading confining pressure

Because of coal seam excavation and periodic disturbance of back-and-forth coal cutting, the surrounding rock is subjected to tiered cyclic unloading and loading. Based on this, a seepage experiment under constant axial stress and tiered cyclic unloading-loading confining pressure was carried out, and two new damage variables were proposed. These results showed that, the accumulative plastic deformations and corresponding permeability increased step-wise with unloading levels, permeability decreased with cycle number in the same unloading level when the unloading level was small, it was the opposite when the unloading level was large. The Kaiser effect and the Felicity effect actually coexisted during the experiment. As the unloading level increased, the relationship between dissipated energy and cycle number converted from logarithm to linear relationship. Two damage variables showed that the critical value of the damage variables for coal failure Dc≈0.9.

The effect of the amount, distribution, and end anchorage conditions of bond beam reinforcement on the behaviour of concrete masonry shear walls

The behaviour of squat shape partially grouted concrete masonry shear walls with fixed-end boundary conditions subjected to constant average axial stress and cyclic lateral loading was investigated. Two replicas were tested of each combination of horizontal reinforcement ratio (0.12%, 0.06%, and 0.03%) and four end anchorage conditions (straight, 90°, 180°, and shear studs). The behaviour of the walls was compared in terms of strength, ductility, stiffness, and dissipated energy. While the effect of horizontal bar size was greater than that of end anchorage, neither improved end anchorage nor smaller bar size increased yielding at critical locations on the rebars. The highest course of the wall should be reinforced and grouted, as that improves performance of the walls. In addition, the amount of horizontal reinforcement did not significantly affect the strength of the shear walls, therefore changes to the shear design equations in the Canadian Standard are recommended.

Experimental Investigation of Spalling Failure of D-Shaped Tunnel Under Three-Dimensional High-Stress Conditions in Hard Rock

The D-shaped cross section is a commonly used tunnel cross section in underground engineering. To simulate the failure process of a D-shaped hole under deep three-dimensional (3D) high-stress conditions, true-triaxial tests were conducted on cubic granite specimens with a through D-shaped hole, and the failure process of the hole sidewall was recorded in real time. Results show that the spalling failure process of the D-shaped hole sidewall can be divided into four periods: calm, fine particle ejection, crack generation and propagation, and rock slab gradually buckling and spalling. Afterwards, symmetrical V-shaped notches were formed on both sidewalls between the corner and arch springing. The spalling failure shows tensile failure characteristics. Under high vertical stress and constant horizontal axial stress, increasing the lateral stress reduces the severity of the spalling failure and the depth of the V-shaped notch. The initial failure vertical stress of the D-shaped hole sidewall is higher than that of circular hole sidewall, and the failure of D-shaped hole sidewall is mainly characterized by static failure. The failure of the circular hole sidewall is a more severe dynamic failure. When the vertical applied stress is the maximum principal stress, the position of the V-shaped notch tip is 0.20–0.25 h (h is the height of the D-shaped tunnel) from the tunnel floor, whereas that in the circular tunnel is 0.5 d (d is the diameter of the circular tunnel) from the tunnel floor. Specific support schemes should therefore be designed for tunnels with different cross sections according to the damage location, depth of failure zone, and severity of failure.

Effectiveness of UHPFRC cover in delaying bar corrosion

Reinforcement corrosion is one of the major factors limiting the service life of reinforced concrete structures. This work investigates the efficiency of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) materials in mitigating corrosion of reinforcement in chloride environments. Variables of the study were, the type of fibers (Steel or PVA) added to a commercial prepackaged dry mix, concrete cover thickness, pre-existing crack widths (0, 0.5 mm and 2 mm) and the presence of constant mechanical axial stress in the exposed bar. Accelerated corrosion of specimens included the application of a constant potential with a 1:3 wet/dry cycle in order to fully oxidize the resulting corrosion byproducts. After several wet/dry cycles, specimens were tested under monotonic tension in order to study the effectiveness of UHPFRC cover in delaying corrosion of embedded reinforcement. One of the major findings was that these materials were able to fully mitigate corrosion in the absence of service cracks, however the effectiveness was gradually reduced with increasing crack width. It was also found that in the presence of cracks, steel-fiber reinforced specimens showed higher resistivity relative to PVA-fiber reinforced specimens owing to the hydrophilic nature of the synthetic fibers which enabled absorption and storage of water in the exposed concrete core.

Mechanical behavior of sandy facies of Opalinus Clay under different load conditions

Abstract The mechanical behavior of sandy facies of Opalinus Clay at the Mont Terri underground rock laboratory (URL) in Switzerland was investigated with drained and undrained triaxial compression and extension, cyclic compression, and creep tests. Samples were taken from boreholes drilled parallel to bedding. Most of the samples were reconditioned to minimize sampling effects of desaturation and micro-cracking. The compression was accomplished by increasing axial stress at constant radial stress. The extension was carried out by increasing radial stress at constant axial stress. Moreover, extension was also achieved by simultaneously increasing radial stress and decreasing axial stress under constant mean stress. The test results showed elastoplastic stress–strain behavior with volumetric compaction until onset of dilatancy at high deviatoric stresses above 80%–90% of the peak failure strength. The strength is dependent upon load path and mean stress. The strength under triaxial compression is higher than that under extension. The respective strength increases with increasing mean stress. Desaturation enhances the stiffness and strength of the claystone. The deformation and strength of the claystone are time-dependent. Under constant deviatoric stress, the claystone crept continuously with time, which can be characterized by a transient phase and a following stationary phase, and even a tertiary phase at high deviatoric stresses to rupture.

Experimental study on strain behavior and permeability evolution of sandstone under constant amplitude cyclic loading‐unloading

AbstractThe coupling of in situ stress, seepage, and fracture makes the strata exhibit complex strain behavior and permeability evolution under the stress path of cyclic loading‐unloading. In this study, the cyclic loading‐unloading experiments of constant amplitude axial stress of sandstone under the combination of different initial confining pressures and loading‐unloading rates are conducted. The experimental results show that the heterogeneity of sandstone, Poisson's ratio produced by adjacent loading‐unloading, and confining pressure determine the deformation characteristics of sandstone in lateral and axial directions. Sandstone can produce significant shear dilatancy at a low rate; this is because stress perturbation can activate more particle slippage and fracture structure changes. However, the fracture preferentially propagates along the end or edge of the crack with strong stress sensitivity to form a shear failure plane at high rate. The normalized permeability of sandstone decreases with an increase in the loading‐unloading rate before failure. The evolution of normalized permeability is closely related to the shear slip of fracture structure and sandstone particles. For the prevention of rock engineering disasters, the high loading‐unloading rate results in lower normalized permeability, which favors the prevention of gas‐type disasters in rocks with higher gas potential energy; however, it is not conducive to the prevention of rockburst.