scholarly journals Analysis of the Damage Characteristics and Energy Dissipation of Rocks with a Vertical Hole under Cyclic Impact Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Bing Dai ◽  
Xinyao Luo ◽  
Li Chen ◽  
Yakun Tian ◽  
Zhijun Zhang ◽  
...  
Keyword(s):  
Tensile Failure ◽  
Impact Loads ◽  
Failure Patterns ◽  
Transverse Tensile ◽  
Splitting Failure ◽  
Axial Splitting ◽  
Cyclic Impact ◽  
Rock Specimens ◽  
Equal Amplitude ◽  
Vertical Hole

This study systematically investigates the failure patterns, energy dissipation, and fracture behavior of rock specimens containing a vertical hole under impact loads. First, an improved damage calculation equation suitable for the analysis of rock specimens with a vertical hole is obtained based on the one-dimensional stress wave theory and the interface continuity condition. After that, the Hopkinson pressure bar (SHPB) device was used to conduct cyclic impact tests with different impact pressures and impact modes (impact pressures with equal amplitude and unequal amplitude). The experimental results suggest that, under the equal-amplitude high pressure and unequal-amplitude pressure, the degree of damage of the rock significantly increased, the bearing capacity greatly reduced, and the rock gradually transitions from having good ductility to experiencing brittle failure. The cumulative specific energy absorption value gradually increases with the increase in the cyclic impact. Compared to that of the equal impact condition, the degree of damage to the rock is more severe for the case of equal-amplitude high pressure and unequal impact, and the failure mode undergoes a transformation from transverse tensile failure to transverse tensile failure-axial splitting failure combination and axial splitting failure. Through the analysis of rock energy changes and rock failure patterns during cyclic impact, it will be helpful to predict and control the fracture caused by local stress concentration during excavation, thus can reduce the cost of support and reinforcement in excavation and improve the stability of surrounding rocks.

Three Dimensional Numerical Approach to Splitting Failure of Rock Discs

2007 ◽  
Vol 353-358 ◽  
pp. 921-924
Author(s):  
Tao Xu ◽  
Tian Hui Ma ◽  
Chun An Tang ◽  
Zheng Zhao Liang
Keyword(s):  
Standardized Test ◽  
Process Analysis ◽  
Failure Process ◽  
Numerical Approach ◽  
Rock Failure ◽  
Test Method ◽  
Tensile Failure ◽  
Numerical Code ◽  
Failure Patterns ◽  
Splitting Failure

The Brazilian splitting tests have been commonly and widely used as a standardized test method on disc or cylinder specimens to measure the indirect tensile strength of rocks in mining engineering and other rock engineering. In this paper, a novel numerical code, 3D Rock Failure Process Analysis code, was applied to implement the splitting tensile failure tests on rock discs. The influences of the heterogeneity on stress distribution in rock are also discussed and the splitting failure patterns of specimens subjected to Brazilian tests are simulated. The simulated splitting results of rock discs were found quite realistic, which indicate that the rock failure analysis method is applicable and practical for the study of rock disc splitting failure.

Resistance of sintered constructional steels to cyclic impact loads

1976 ◽  
Vol 15 (11) ◽  
pp. 884-887
Author(s):  
O. O. Peterson ◽  
V. A. Pekhovich ◽  
L. P. Saifulina
Keyword(s):  
Impact Loads ◽  
Cyclic Impact

scholarly journals Evolution Mechanism of Deformation and Failure of Surrounding Rock during Excavation and Unloading of the High-Stress Rock Mass

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Wensong Xu ◽  
Guangming Zhao ◽  
Chongyan Liu ◽  
Xiangrui Meng ◽  
Ruofei Zhang ◽  
...  
Keyword(s):  
Rock Mass ◽  
High Stress ◽  
Surrounding Rock ◽  
Critical Conditions ◽  
Safety Control ◽  
Rock Samples ◽  
Failure Patterns ◽  
Failure Evolution ◽  
Splitting Failure ◽  
Confining Pressures

To deeply analyze the failure evolution of surrounding rock during excavation-induced unloading of the high-stress rock mass, a multistage failure model was established based on revealed failure patterns. The critical conditions for wing cracks were determined. The slab crack buckling analysis was carried out. The true-triaxial rockburst testing system was used for the miniature model test to study the fracturing evolution of surrounding rocks during excavation-induced unloading of the high-stress rock mass. The research results indicated that harder rock samples had higher compressive strength. Moreover, the smaller peak strains implied more obvious yield/plastic stages of harder rock samples with high confining pressures and softer rock samples with low confining pressures. V-shaped grooves appeared at the beginning of the surrounding rock’s failure while spalling and splitting occurred as the stress increased. Finally, the entire sample’s overall splitting failure was observed, and the borehole bottom bulged upward. The harder rock masses had fewer fractures and higher degrees of failure. There were obvious V-shaped grooves on both sides of the marble cave wall. The tensile failure occurred near the opening surface and shear failure at a far distance. The sandstone's overall failure was related to tensile cracking, and splitting failure occurred far away from the opening surface, which was similar to the in situ failure of surrounding rocks during excavation-induced unloading of the high-stress rock mass. The results obtained are instrumental in the construction safety control and prevention of underground engineering disasters.

Resistance of maraging steel N18K9M5T to cyclic impact loads

1975 ◽  
Vol 17 (7) ◽  
pp. 584-588
Author(s):  
A. Ya. Maloletnev ◽  
Yu. B. L'vov ◽  
I. V. Pestov ◽  
M. D. Perkas
Keyword(s):  
Maraging Steel ◽  
Impact Loads ◽  
Steel N18k9m5t ◽  
Cyclic Impact ◽  
Maraging Steel N18k9m5t

scholarly journals Experimental Study of Brazilian Tensile Strength of Concrete Under Static Loads

2020 ◽  
Vol 206 ◽  
pp. 01018
Author(s):  
Rui Li ◽  
Lei Liu ◽  
Zhihua Zhang ◽  
Huaming An
Keyword(s):  
Tensile Strength ◽  
Testing Machine ◽  
Damage Index ◽  
Modern Society ◽  
Strength Test ◽  
Test Method ◽  
Tensile Failure ◽  
Brazilian Tensile Strength ◽  
Failure Patterns ◽  
Tensile Strength Test

Concrete is one of the most significant materials in modern society. It is widely used in many projects. Thus it is essential to study the strength and the failure patterns of this material. As well known, the compressive strength is much higher than the tensile strength for concrete. Thus, it is easy to fail due to the tensile strength for concrete. Thus, this paper focuses on the study of the tensile strength of the concrete and its failure patterns. Three types of concretes are made for studying the tensile strengths and the failure patterns of the concretes. Then the Brazilian tensile strength test method is employed in this study. The mythology of calculating tensile strength by the Brazilian tensile strength test method is introduced. Many discs are made for the tests. The Rock mechanics testing machine is used to excavate pressure on the top and bottom of the disc. It is concluded that the failure of the disc is along the vertical diameter between the top and bottom plates contacting the dis. The tensile failure is not obviously influenced by the ratios of the materials while the tensile strength is significantly influenced by the ratios of the concrete. The damage index of concrete is also proposed to describe the capabilities of resisting failure.

Experimental and numerical study on crack propagation and coalescence in rock-like materials under compression

2021 ◽  
pp. 030932472098691
Author(s):  
Xiaojing Li ◽  
Yifan Bai ◽  
Xudong Chen ◽  
Xinning Zhao ◽  
Mingying Lv
Keyword(s):  
Shear Failure ◽  
Numerical Study ◽  
Reference Value ◽  
Peak Stress ◽  
Tensile Failure ◽  
Wing Crack ◽  
Splitting Failure ◽  
Single Cross ◽  
Initiation Sequence ◽  
Double Cross

The discontinuous crack surface in a rock affects the stability of the whole rock system. The experiments in this paper were carried out by prefabricating rock-like specimens with different types of flaws, then the specimens were tested under uniaxial compression. Moreover, based on the theory of particle flow, PFC2D software was used for numerical simulation, and the comparative analysis of the experimental and simulative results was carried out to obtain the crack initiation sequence, propagation phenomenon, and failure mode of rock specimens with different flaw types. The results indicated that the wing crack started at the tip of flaw and the form of crack assumed split failure, followed by shear failure caused by the secondary crack. The tensile failure degree decreases and the influence of shear failure increases with the increase of flaw angle. The wing crack and secondary initiation stress value is 35%–55% and 85%–95% of the peak stress value. Crack coalescence appeared in adjacent flaws of rock-like specimens with multiple parallel single flaws, single-cross flaws and double-cross flaws, and the coalescence phenomenon always occurs when the stress peak value is reached. With the number of flaws increasing, the splitting failure of rock-like specimens became more and more serious, the splitting failure of double cross-flaw specimen is the most serious. As for the specimen with single-cross flaw, the wing crack would be produced at the tip of the flaw with larger obliquity. The results of this paper may offer certain reference value for the study on the mechanism of rock crack.

scholarly journals Numerical tests on thermal cracking characteristics of rocks with different scales

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879214 ◽  
Author(s):  
Yang Xiao ◽  
Rui Zhao ◽  
Qing-Xiang Huang ◽  
Jun Deng ◽  
Jun-Hui Lu
Keyword(s):  
Acoustic Emission ◽  
Thermal Destruction ◽  
Thermal Damage ◽  
Process Analysis ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Thermal Cracking ◽  
Tensile Failure ◽  
Failure Patterns ◽  
Different Diameters

Realistic failure process analysis, a thermal software simulation, was used to explore the scale effect of thermal cracking of rock under the thermal–mechanical coupling loading. The patterns and characteristics of thermal destruction were analyzed by simulating the thermal cracking of rocks with the same diameter different lengths, the same length but different diameters, and the same size ratio but different sizes (same length/diameter ratio but with different diameters). The acoustic emission and energy changes were also studied during thermal destruction. The results represented that the main forms of thermal cracking are tensile failure and shear failure. The smaller the scale is (length, diameter, and size), the more complex the pattern of thermal damage exhibited as failure patterns of inverted “S” or “V.” With the increasing scale, thermal damage models were simpler. The elastic modulus was determined by the diameter of specimens, and the peak stress was determined by the length of specimens. Overall, as the scale increased, the stress intensity decreased, but the number of acoustic emissions and acoustic emission energy and the corresponding accumulation increased.

scholarly journals Experimental Study on the Mechanical Properties and Damage Evolution of Hollow Cylindrical Granite Specimens Subjected to Cyclic Coupled Static-Dynamic Loads

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yongming Xue ◽  
Bing Dai ◽  
Ying Chen ◽  
Lei Zhang ◽  
Guicheng He ◽  
...  
Keyword(s):  
High Speed ◽  
Shear Failure ◽  
Rock Specimen ◽  
Split Hopkinson Pressure Bar ◽  
Wave Theory ◽  
Strengthening Effect ◽  
Hopkinson Pressure Bar ◽  
Transverse Cracks ◽  
Cyclic Impact ◽  
Rock Specimens

To study the characteristics of roadway surrounding rock damage caused by frequent disturbances under different static stress conditions, cyclic impact tests on granite with vertical holes under different axial prestress conditions were performed by a modified split Hopkinson pressure bar test, and the damage of the specimens was recorded with a high-speed camera process. The test results show that under the same air pressure cyclic impact, the rock specimens mainly undergo the compaction-fatigue-failure transition. As the axial prestress increases, the compaction-fatigue phase gradually weakens, and the dynamic compressive strength decreases. When the axial prestress is 42% of the UCS and 62% of the UCS, the rock specimen shows a certain “strengthening” effect during the initial cyclic impact stage. During the failure of the rock specimens, the axial prestressing effect limited the initiation of some transverse cracks, and a mixed tensile-shear failure mode appeared. The rock specimens with an axial prestress of 62% of the UCS showed energy release during cyclic impact. To some extent, the probability of “rock bursts” has been induced. Based on the one-dimensional stress wave theory, the damage variables of wave impedance during the cyclic impact loading of the rock with vertical holes are defined. It is found that when the rock specimen is in the stage of compaction and fatigue damage, the damage is small, and the damage is even reduced.

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