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 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.

Numerical Calculation of Micro-Plie in Slope Engineering

2014 ◽  
Vol 644-650 ◽  
pp. 5113-5120
Author(s):  
Xiao Song Tang ◽  
Jian Ping Xin ◽  
Ying Ren Zheng
Keyword(s):  
Shear Failure ◽  
Bending Moment ◽  
Soil Mass ◽  
Calculation Model ◽  
Plastic State ◽  
Soil Slope ◽  
Structural Element ◽  
Deformation And Failure ◽  
Pile Deformation ◽  
Rock And Soil

In order to conduct the numerical simulation of rock and soil slope strengthened by the micro-pile with reinforced bar, FEM strength reduction is combined with the program of FLAC which possesses the function of analyzing tensile and shear failure. The micro-pile is under plastic state due to its mechanic features. Solid element and ideal elastic-plastic constitutive model of Mohr-Coulomb are applied as the rock and soil mass and pile. The calculation model can work out the safety factor of slope, the dynamic changing process of pile deformation and failure, the failure mode of slope after strengthened by micro-pile. Then the structural element of pile is used to simulate piles, which can obtain the bending moment and shear force. The beam element is used to simulate the coupling beam. So the layout principle of inner force before the failure can be calculated.

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 An Experimental Study of the Uniaxial Failure Behaviour of Rock-Coal Composite Samples with Pre-existing Cracks in the Coal

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Shaojie Chen ◽  
Yao Ge ◽  
Dawei Yin ◽  
Huisan Yang
Keyword(s):  
Crack Propagation ◽  
Composite Structure ◽  
Shear Failure ◽  
Progressive Failure ◽  
Strain Curve ◽  
Composite Sample ◽  
Compression Tests ◽  
Failure Characteristics ◽  
Splitting Failure ◽  
Composite Samples

Many hazards encountered during coal mining can be caused by the instability and failure of the composite structure of the coal seam and the surrounding rock strata. The defects present in the coal affect the structural stability of the composite structure. In this study, uniaxial compression tests were conducted on sandstone-coal composite samples with pre-existing cracks in the coal, combined with tests performed with an acoustic emission (AE) device and a digital video camera. The strength, macrofailure initiation (MFI), and failure characteristics of composite samples, as influenced by the coal’s pre-existing cracks, were analysed. The coal’s pre-existing cracks were shown to reduce the strength, promote the occurrence of MFI, and affect the failure characteristics of the samples. Vertical penetration cracks had much more pronounced effects on strength and MFI occurrence, especially vertical penetration cracks that penetrated through the centre of the coal. Horizontal penetration cracks had a much reduced effect on strength and MFI occurrence. The MFI caused a step shape in the stress-strain curve accompanied with a peak energy index signal and occurred around the original coal cracks. The MFI models predominantly exhibited crack initiation from the pre-existing coal cracks and surface spalling caused by crack propagation. The intact composite sample failure presented as an instantaneous failure, whereas the composite samples containing the pre-existing cracks showed a progressive failure. The failures of composite samples occurred predominantly within the coal and displayed an X-typed shear failure accompanied by a small splitting failure. Both the coal and sandstone were destroyed in the composite sample with vertical penetration cracks through the centre of the coal. Failure of the coal occurred through a splitting failure accompanied by a small X-typed shear failure, while the sandstone showed a splitting failure induced by crack propagation in the coal.

scholarly journals Deformation and failure characteristics of weathered granite under uniaxial compression

AIP Advances ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 075222 ◽  
Author(s):  
Lingfan Zhang ◽  
Duoxing Yang ◽  
Zhonghui Chen
Keyword(s):  
Uniaxial Compression ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Weathered Granite

scholarly journals An Evaluation Method of Brittleness Characteristics of Shale Based on the Unloading Experiment

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1779 ◽  
Author(s):  
Xiaogui Zhou ◽  
Haiming Liu ◽  
Yintong Guo ◽  
Lei Wang ◽  
Zhenkun Hou ◽  
...  
Keyword(s):  
Evaluation Method ◽  
Shear Failure ◽  
Confining Pressure ◽  
Shear Zones ◽  
Loading Path ◽  
Mechanical Parameters ◽  
Failure Characteristics ◽  
Unloading Rate ◽  
Uplift And Erosion ◽  
Unloading Effect

Shale reservoir has an initial unloading effect during the natural uplift and erosion process, which causes the shale brittleness to change, affecting the design of the fracturing scheme. To consider this, the axial compression loading and confining pressure unloading experiment of shale is carried out, and then the influence of unloading rate on the mechanical parameters, failure characteristics, and the brittleness of rock are analyzed. What is more, a new evaluation method of brittleness characteristics that take the unloading effect into consideration is proposed. The conclusions are as follows: (1) The unloading rate has a weakening effect on the mechanical parameters, such as the destructive confining pressure and the residual strength of the samples. (2) The failure characteristics of shale specimens are a single shear failure in an oblique section under low unloading rate, and multiple shear zones accompanied with bedding fracture under high unloading rate. (3) The brittleness of shale samples is well verified by the brittleness index B d 1 and B d 2 during the loading path; nevertheless, it has shortage at the unloading path. This paper proposes a new brittleness evaluation method which can consider the influence of the different unloading rates and unloading points. Furthermore, there is a nice characterization between the brittleness damage and this method.

scholarly journals Experimental Investigation on Time-Frequency Characteristics of Microseismic Signals in the Damage Evolution Process of Coal and Rock

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 809
Author(s):  
Wei Yang ◽  
Chengwu Li ◽  
Rui Xu ◽  
Xunchang Li
Keyword(s):  
Damage Evolution ◽  
Resonance Effect ◽  
Low Frequency ◽  
Dominant Frequency ◽  
Frequency Characteristics ◽  
Evolution Process ◽  
Deformation And Failure ◽  
Time Frequency ◽  
Rock Materials ◽  
Damage Degree

The deformation and failure of coal and rock materials is the primary cause of many engineering disasters. How to accurately and effectively monitor and forecast the damage evolution process of coal and rock mass, and form a set of prediction methods and prediction indicators is an urgent engineering problems to be solved in the field of rock mechanics and engineering. As a form of energy dissipation in the deformation process of coal and rock, microseismic (MS) can indirectly reflect the damage of coal and rock. In order to analyze the relationship between the damage degree of coal and rock and time-frequency characteristics of MS, the deformation and fracture process of coal and rock materials under different loading modes was tested. The time-frequency characteristics and generation mechanism of MS were analyzed under different loading stages. Meanwhile, the influences of properties of coal and rock materials on MS signals were studied. Results show that there is an evident mode cutoff point between high-frequency and low-frequency MS signals. The properties of coal and rock, such as the development degree of the original fracture, particle size and dense degree have a decisive influence on the amplitude, frequency, energy and other characteristic parameters of MS signals. The change of MS parameters is closely related to material damage, but has no strong relation with the loading rate. The richness of MS signals before the main fracture depends on the homogeneity of materials. With the increase of damage, the energy release rate increases, which can lead to the widening of MS signals spectrum. The stiffness and natural frequency of specimens decreases correspondingly. Meanwhile, the main reason that the dominant frequency of MS detected by sensors installed on the surface of coal and rock materials is mainly low-frequency is friction loss and the resonance effect. In addition, the spectrum and energy evolution of MS can be used as a characterization method of the damage degree of coal and rock materials. Furthermore, the results can provide important reference for prediction and early warning of some rock engineering disasters.

scholarly journals Deformation and Failure Behavior of Wooden Sandwich Composites with Taiji Honeycomb Core under a Three-Point Bending Test

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2325 ◽  
Author(s):  
Jingxin Hao ◽  
Xinfeng Wu ◽  
Gloria Oporto ◽  
Jingxin Wang ◽  
Gregory Dahle ◽  
...  
Keyword(s):  
Shear Failure ◽  
Dominant Role ◽  
Honeycomb Structure ◽  
Structure Design ◽  
Bending Test ◽  
Failure Behavior ◽  
Sandwich Composites ◽  
Honeycomb Core ◽  
Deformation And Failure ◽  
Three Point Bending

A new type of Taiji honeycomb structure bonded outside with wood-based laminates was characterized from a mechanical standpoint. Both theoretical and experimental methods were employed to analyze comprehensively the deformation behavior and failure mechanism under a three-point bending test. The analytical analysis reveals that a Taiji honeycomb has 3.5 times higher strength in compression and 3.44 times higher strength in shear compared with a traditional hexagonal honeycomb. Considering the strength-weight issue, the novel structure also displays an increase in compression strength of 1.75 times and shear strength of 1.72 times. Under a three-point bending test, indentation and core shear failure played the dominant role for the total failure of a wooden sandwich with Taiji honeycomb core. Typical face yield was not observed due to limited thickness-span ratio of specimens. Large spans weaken the loading level due to the contribution of global bending stress in the compressive skin to indentation failure. A set of analytical equations between mechanical properties and key structure parameters were developed to accurately predict the threshold stresses corresponding to the onset of those deformation events, which offer critical new knowledge for the rational structure design of wooden sandwich composites.

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