scholarly journals Deformation and Failure Characteristics of Sandstone Subjected to True-Triaxial Unloading: An Experimental and Numerical Study

2021 ◽  
Author(s):  
Fan Xiao ◽  
De-Yi Jiang ◽  
Fei Wu ◽  
Jie Chen ◽  
Jian-Zhi Zhang ◽  
...  
Keyword(s):  
Shear Failure ◽  
Numerical Study ◽  
Tensile Force ◽  
Tensile Fracture ◽  
Sandstone Sample ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Material Inhomogeneity ◽  
Micro Cracks

The influence of maximum principal stress level on true-triaxial unloading behaviors and the failure mechanism of sandstone samples were comprehensively investigated by laboratory tests and discrete element simulations. The results show that the level of σ1 at unloading point significantly affects the deformation and failure characteristics of sandstone samples under true-triaxial unloading conditions. As the level of σ1 at unloading point increases, the ultimate bearing capacity of sandstone sample is increasingly strengthened, while the sample collapses more easily during the unloading process, and the failure mode of sandstone sample changes from mixed tensile-shear failure to shear failure. With the increase in the level of σ1 at unloading point, the accumulative micro-cracks at the unloading point and micro-crack generation rate during the unloading phase exhibit an increasing trend, while the sum of micro-cracks at the unloading phase and the ratio between the amount of tensile micro-cracks and shear micro-cracks roughly show a downward trend. The formation of macro fracture in sandstone sample is closely related to the stress conditions and material inhomogeneity. The tensile fracture in the upper right part of sample when the level of σ1 is relatively low should be attributed to the superiority in tensile contacts between particles in terms of contact number and corresponding tensile force.

scholarly journals Experimental study on deformation and failure characteristics of discontinuous prefabricated fractured tuff

2019 ◽  
Vol 16 (5) ◽  
pp. 862-874
Author(s):  
Yang Song ◽  
Heping Wang ◽  
Meng Ren
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Dissipated Energy ◽  
Uniaxial Compression Test ◽  
Tensile Shear ◽  
Joint Spacing ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Peak Intensity ◽  
Dip Angle

Abstract To study more fully the characteristic law of deformation and failure of tuff jointed rock mass of prefabricated parallel discontinuous joint test specimens, the uniaxial compression test was used. The stress–strain curve, peak intensity, deformation parameters, energy characteristics, etc., of the rock test specimens were systematically studied under different combinations of joint dip angle and joint spacing. The research found that: (1) during the failure process of tuff, the peak intensity and elastic modulus followed a U-shaped change pattern and the minimum value was reached when α = 60°; (2) the fracture modes of test specimens with different joint dip angles were different. When α = 30° and 45°, failure characteristics were mixed modes of tensile or tensile shear failure. When α = 60°, failure characteristics were shear. At α = 75°, the failure characteristic was tensile shear failure. (3) The absorbed and dissipated energy of the rock increased nonlinearly at each stage of deformation. (4) We quantified rock energy damage through a correlation between dissipated energy and absorbed energy of the rock in the process of energy evolution, and obtained an evolution of the relationship between the dissipated energy ratio, crack dip angle and crack spacing. Based on different fracture distribution methods and according to the strain equivalence principle, the constitutive equation of the pre-peak rock damage was obtained.

scholarly journals Experimental Study on the Deformation and Failure Characteristics of Anchor under Graded Loading and Corrosion

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Guanglin Sun ◽  
Jiangchun Hu ◽  
Hongfang Wang ◽  
Pengfei Li
Keyword(s):  
Shear Failure ◽  
Load Condition ◽  
Working Environment ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Damage Degree ◽  
Splitting Failure ◽  
Safety And Stability ◽  
And Diffusion ◽  
Rock And Soil

During the entire life cycle of rock and soil anchors, owing to the influence of adverse factors such as the working environment, load change, and anchor performance degradation, the working load of the anchor will continue to increase and the mechanical properties will continue to deteriorate, which significantly affects the safety and stability of rock and soil anchors. Therefore, this study focuses on the deformation and failure characteristics of anchors under loading and corrosion conditions by means of indoor simulation tests under laboratory conditions. The results indicate the following. (1) There are obvious cracks on the surfaces of specimens 2# and 10#. In the two groups of specimens, the corroded bolt surface exhibited a corrosion phenomenon. This indicates that the corrosion environment conditions cause a certain degree of damage to the anchored rock mass. (2) Under the same gradient load condition, three observable cracks were found in the 10# anchorage specimens and one observable crack was found in the 2# anchorage specimens. Therefore, it is clear that the damage degree of the anchor increases with an increase in the corrosion time. (3) Under the condition of corrosion environment, the strain in the lower part of the specimen is generally greater than that in the upper part of the specimen, and the failure of this group of specimens in the loading process is mostly splitting failure, which is basically generated along the trend of the strain nephogram, and shear failure occurs with the extension and diffusion of cracks.

scholarly journals Experimental and Numerical Study of Strength and Failure Behavior of Precracked Marble under True Triaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yong Han ◽  
Yuemao Zhao ◽  
Jinglong Li
Keyword(s):  
Shear Failure ◽  
Numerical Study ◽  
Triaxial Compression ◽  
Numerical Results ◽  
Peak Strength ◽  
Failure Behavior ◽  
Compression Tests ◽  
True Triaxial ◽  
Fracturing Process ◽  
True Triaxial Compression

Cracks play an important role in evaluating the strength and failure behavior of engineering rock mass. In order to increase the understanding of strength and failure mechanism of precracked rock, crack propagation and coalescence from preexisting cracks under true triaxial compression are investigated using true triaxial compression tests and Cellular Automata Software for engineering Rockmass fracturing process (CASRock). Three types of specimens were studied experimentally and numerically. Experimental and numerical results show that both the preferential angle and areal intensity of preexisting cracks can affect the compressive strength and failure behavior of the specimens. The peak strength firstly decreases and then increases with increase of the preferential angle. Also, the peak strength nonlinearly decreases with the increase of cracks’ areal intensity. The numerical results show that the crack initiation and coalescence are observed and characterized from the inner and outer tips of preexisting cracks in specimens containing single crack and multiple parallel cracks. The main shear failure in the specimen containing multiple unparallel preexisting cracks initiate and propagate from one of the macroscopic preexisting cracks, and other preexisting cracks do not initiate, propagate, and coalesce until reaching the peak strength.

scholarly journals Influence of Patching on the Shear Failure of Reinforced Concrete Beam without Stirrup

2021 ◽  
Vol 6 (7) ◽  
pp. 97
Author(s):  
Stefanus Adi Kristiawan ◽  
Halwan Alfisa Saifullah ◽  
Agus Supriyadi
Keyword(s):  
Reinforced Concrete ◽  
Shear Failure ◽  
Numerical Study ◽  
Unsaturated Polyester ◽  
Reinforced Concrete Beam ◽  
Concrete Cover ◽  
Shear Capacity ◽  
Rc Beam ◽  
Shear Span ◽  
Shear Cracking

Deteriorated concrete cover, e.g., spalling or delamination, especially when it occurs at the web of a reinforced concrete (RC) beam within the shear span, can reduce the shear capacity of the beam. Patching of this deteriorated area may be the best option to recover the shear capacity of the beam affected. For this purpose, unsaturated polyester resin mortar (UPR mortar) has been formulated. This research aims to investigate the efficacy of UPR mortar in limiting the shear cracking and so restoring the shear capacity of the deteriorated RC beam. The investigation is carried out by an experimental and numerical study. Two types of beams with a size of 150 × 250 × 1000 mm were prepared. The first type of beams was assigned as a normal beam. The other was a beam with a cut off in the non-stirrup shear span, which was eventually patched with UPR mortar. Two reinforcement ratios were assigned for each type of beams. The results show that UPR mortar is effective to hamper the propagation of diagonal cracks leading to increase the shear failure load by 15–20% compared to the reference (normal) beam. The increase of shear strength with the use of UPR mortar is consistently confirmed at various reinforcement ratios.

Research on Sticking Failure Characteristics of Cemented Carbide Blade

2012 ◽  
Vol 500 ◽  
pp. 211-217
Author(s):  
Zhe Li ◽  
Min Li Zheng ◽  
Xian Zhi Chen ◽  
Meng Tong
Keyword(s):  
Electron Microscopy ◽  
Cutting Tool ◽  
Influence Factors ◽  
Rake Face ◽  
Tool Breakage ◽  
Failure Characteristics ◽  
Micro Cracks ◽  
Cutting Zone ◽  
Element Density ◽  
Scanning Electron

Through the analysis on damaged tool in sticking failure experiment by cutting austenitic stainless steel (1Cr18Ni9Ti) with scanning electron microscopy (SME), found that there are micro cracks existent on rake face near the tip of the cutting tool, through the research of the emergence, development and distribution direction of the crack, the direct reason for tool breakage is the crack being out of control. Combining the study of cutting tool element density change in cutting zone and grooving wear on rake face, this paper analyzed the cause of the binding between chip and tool and the influence factors of sticking failure during the cutting process.

scholarly journals Experimental Test on Nonuniform Deformation in the Tilted Strata of a Deep Coal Mine

2021 ◽  
Vol 13 (23) ◽  
pp. 13280
Author(s):  
Hai Wu ◽  
Qian Jia ◽  
Weijun Wang ◽  
Nong Zhong ◽  
Yiming Zhao
Keyword(s):  
High Stress ◽  
Stability Control ◽  
Surrounding Rock ◽  
Experimental Results ◽  
Lower Side ◽  
Reinforcement Scheme ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Deep Mine ◽  
Deep Coal Mine

Taking a deep-mine horizontal roadway in inclined strata as our research object, the true triaxial simulation technique was used to establish a model of the inclined strata and carry out high-stress triaxial loading experiments. The experimental results show that the deformation of surrounding rock in the roadway presents heterogeneous deformation characteristics in time and space: the deformation of the surrounding rock at different positions of the roadway occurs at different times. In the process of deformation of the surrounding rock, deformation and failure occur at the floor of the roadway first, followed by the lower shoulder-angle of the roadway, and finally the rest of the roadway. The deformation amount in the various areas is different. The floor heave deformation of the roadway floor is the greatest and shows obvious left-right asymmetry. The deformation of the higher side is greater than that of the lower side. The model disassembly shows that the development of cracks in the surrounding rock is characterized by more cracks on the higher side and fewer cracks on the lower side but shows larger cracks across the width. The experimental results of high-stress deformation of the surrounding rock are helpful in the design of supports, the reinforcement scheme, and the parameter optimization of roadways in high-stress-inclined rock, and to improve the stability control of deep high-stress roadways.

scholarly journals Numerical Study of Fracture Characteristics of Deep Granite Induced by Blast Stress Wave

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Zheming Zhu ◽  
Weiting Gao ◽  
Duanying Wan ◽  
Meng Wang ◽  
Yun Shu
Keyword(s):  
Shear Failure ◽  
Numerical Study ◽  
Numerical Models ◽  
Rock Fracture ◽  
Initial Pressure ◽  
3D Models ◽  
In Situ Stress ◽  
Vertical Pressure ◽  
The Difference ◽  
Radial Cracks

To study the characteristics of rock fracture in deep underground under blast loads, some numerical models were established in AUTODYN code. Weibull distribution was used to characterize the inhomogeneity of rock, and a linear equation of state was applied to describe the relation of pressure and volume of granite elements. A new stress initialization method based on explicit dynamic calculation was developed to get an accurate stress distribution near the borehole. Two types of in situ stress conditions were considered. The effect of heterogeneous characteristics of material on blast-induced granite fracture was investigated. The difference between 2D models and 3D models was discussed. Based on the numerical results, it can be concluded that the increase of the magnitude of initial pressure can change the mechanism of shear failure near the borehole and suppress radial cracks propagation. When initial lateral pressure is invariable, with initial vertical pressure rising, radial cracks along the acting direction of vertical pressure will be promoted, and radial cracks in other directions will be prevented. Heterogeneous characteristics of material have an obvious influence on the shear failure zones around the borehole.

Sign in / Sign up

Export Citation Format

Share Document