scholarly journals Numerical Analysis of the Mechanical Behavior and Failure Mode of Jointed Rock under Uniaxial Tensile Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yang Zhao ◽  
Yongning Wu ◽  
Qing Xu ◽  
Lishuai Jiang ◽  
Wanpeng Huang ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Failure Mode ◽  
Failure Modes ◽  
Tensile Tests ◽  
Jointed Rock ◽  
Rock Joints ◽  
Tensile Failure ◽  
Uniaxial Tensile ◽  
Direct Tensile ◽  
Rock Specimens

In the field of rock engineering, tensile failure is one of the most significant failure modes due to the presence of joints/fractures. However, due to the limitations of current laboratory testing, it is difficult to carry out direct tensile tests on jointed rock specimens in the laboratory. To study the effect of joints on the mechanical behavior and failure mode of jointed rock specimens, a three-point modeling method that can consider arbitrarily arranged rock joints is deduced and applied to discrete element simulation. The effects of different joint angles (the inclination angle α, rotation angle β, and superimposed angle γ of α and β, where γ is the angle between the joint and horizontal plane), the density (n), and the rate of cutting area (RCA) of the specimen loading surface (LSS) on the tensile strength (σt), elastic modulus in tension (Et), and failure mode of the specimens were analyzed. The results show that the joint angle (considering α, β, and γ) and RCA have a significant effect on the resulting σt and failure mode, while n has a significant effect on Et. The failure mode of the specimen changes from tensile failure along the joint to direct tensile failure of the specimen as γ increases, and the mechanical behavior transitions from unstable to stable. In addition, the main influence of γ on the mechanical behavior of specimens is revealed, and the change process of the failure mode after the cutting of the LSS is analyzed. The present research can be utilized for multiple purposes, including the joint development of surrounding rock and failure dominated by tensile failure in underground engineering, especially for tunnels, roadways, chambers, and so forth.

Failure Characteristics of Rock-Like Material with Multi-Fissures under Uniaxial Compression

2014 ◽  
Vol 711 ◽  
pp. 129-132
Author(s):  
Ri Hong Cao ◽  
Ping Cao ◽  
Pi Hua Wen ◽  
Rui Wen Chen
Keyword(s):  
Mechanical Behavior ◽  
Failure Mode ◽  
Distribution Density ◽  
Failure Modes ◽  
Jointed Rock ◽  
Similar Material ◽  
Failure Characteristics ◽  
Micro Cracks ◽  
Inclination Angles ◽  
Main Factor

Mechanical behavior and failure mode of jointed rock is one of the significant researches in rock mechanics field. In this work, combined with similar material testing and discrete element numerical method(PFC) to investigate the mechanical behavior and failure mode of the rock-like materials with multi-fissures. The numerical analyses agree well with physical experimentation. It is found that, fissures will weaken the strength of the rock-like material, and when the angle of the fissures is about 25°, the strength of the material reaches a minimum value. The weakening effect of fissure on specimen strength would decrease gradually along with the increase of fissure angle. Compared with the effects of fissure angle, the influence of cracks number to the strength is relatively small. The fissure inclination angle was the main factor of the failure modes. With the different fissure inclination angles, the crack tip of Micro-cracks presents different developmental pattern. However, the influence of fissure distribution density on the failure mode mainly reflects at the fracture penetration mode.

scholarly journals Particle Flow Simulation of the Strength and Failure Characteristics of a Layered Composite Rock-Like Sample with a Single Hole

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1132
Author(s):  
Guozhu Wang ◽  
Yu Wang ◽  
Lei Song ◽  
Hao Shi ◽  
Mingwei Zhang ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Surrounding Rock ◽  
Tensile Failure ◽  
Practical Significance ◽  
Rock Masses ◽  
Engineering Structures ◽  
Layered Rock

Layered rock masses with holes are common in nature. Their mechanical behavior plays an important role in the safety and stability of engineering structures. However, previous studies have concentrated on a single lithological layer, and few studies have reported on the mechanical behavior of layered rock masses with holes. Based on the concept of symmetry, uniaxial compression tests and numerical simulations were performed on rock-like specimens with three layers and a hole in the interlayer. The hole was in the center of the sample and was symmetrical up and down. The influence of the thickness and strength of the interlayer on the mechanical behavior and failure processes of the layered rock masses with holes was investigated. The results show that the peak strength and elastic modulus were associated with the thickness and strength of the interlayer. Three failure modes were observed in the specimens, which were not only related to the thickness and strength of the interlayer, but also affected by the presence of the hole. When the thickness of the interlayer is small, mainly a single failure mode was observed (tensile failure or shear failure). However, when the interlayer was thick, the failure mode was tension-shear mixed failure. The failure mechanism of the specimens was primarily crack propagation at the edge of the hole. These research results can provide a basis for site selection, and the design of surrounding rock protection and support parameters, and thus have important practical significance for improving surrounding rock stability and ensuring construction safety.

Test Study on Dynamic Mechanical Property of Jointed Rock Mass

2013 ◽  
Vol 868 ◽  
pp. 282-286 ◽  
Author(s):  
Li Min Zhang ◽  
Shu Ran Lv ◽  
Hong Yan Liu
Keyword(s):  
Rock Mass ◽  
Failure Mode ◽  
Failure Modes ◽  
Dynamic Strength ◽  
Strain Ratio ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Tensile Failure ◽  
Dip Angle ◽  
Joint Center

Failure modes of jointed rock mass with different joint dip angle, joint center continuity degree, joint sets, load strain ratio and joint filling width under SHPB test are studied with model tests. The results show that failure modes and dynamic strength of jointed rock mass are much related to joint geometry. To rock mass with a single joint, its strength and failure mode are greatly controlled by the joint dip angle. The dynamic strength of the samples with joint dip angle 0° and 90°, whose failure modes are both tensile failure, is 90% and 71% of that of intact one, respectively. The dynamic strength of the samples with joint dip angle 60° is nearly zero. The dynamic strength of the samples with joint dip angle 30° and 45°, whose failure modes are mainly shear failure with partly tensile failure, is 50% and 18% of that of intact ones, respectively. The dynamic strength of the samples with 1/4, 1/2 and 4/5 joint center continuity degree is 95%, 74% and 28% of that of intact one, respectively. The dynamic strength of the samples with 1, 2 and 3 sets of joints is 54%, 23% and 10% of that of intact one, respectively. The dynamic strength of the intact and jointed samples both increases with load strain ratio, and the sensitivity to load strain ratio of the former is much higher than that of the latter, whose failure mode becomes more complicated accordingly. With increase of joint fillings width, the samples dynamic strength decreases gradually, but its failure mode does not change.

Comprehensive study on mechanical properties of coated biaxial warp-knitted fabrics

2021 ◽  
pp. 073168442110204
Author(s):  
Bin Yang ◽  
Yingying Shang ◽  
Zeliang Yu ◽  
Minger Wu ◽  
Youji Tao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Least Squares Method ◽  
Tensile Tests ◽  
Tensile Creep ◽  
Base Layer ◽  
Sustained Load ◽  
Uniaxial Tensile ◽  
Membrane Structures ◽  
Knitted Fabrics

In recent years, coated fabrics have become the major material used in membrane structures. Due to the special structure of base layer and mechanical properties, coated biaxial warp-knitted fabrics are increasingly applied in pneumatic structures. In this article, the mechanical properties of coated biaxial warp-knitted fabrics are investigated comprehensively. First, off-axial tensile tests are carried out in seven in-plane directions: 0°, 15°, 30°, 45°, 60°, 75°, and 90°. Based on the stress–strain relationship, tensile strengths are obtained and failure modes are studied. The adaptability of Tsai–Hill criterion is analyzed. Then, the uniaxial tensile creep test is performed under 24-h sustained load and the creep elongation is calculated. Besides, tearing strengths in warp and weft directions are obtained by tearing tests. Finally, the biaxial tensile tests under five different load ratios of 1:1, 2:1, 1:2, 1:0, and 0:1 are carried out, and the elastic constants and Poisson’s ratio are calculated using the least squares method based on linear orthotropic assumption. Moreover, biaxial specimens under four load ratios of 3:1, 1:3, 5:1, and 1:5 are further tensile tested to verify the adaptability of linear orthotropic model. These experimental data offer a deeper and comprehensive understanding of mechanical properties of coated biaxial warp-knitted fabrics and could be conveniently adopted in structural design.

scholarly journals Tensile Behaviour of FRCM Composites for Strengthening of Masonry Structures—An Experimental Investigation

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3626
Author(s):  
Łukasz Hojdys ◽  
Piotr Krajewski
Keyword(s):  
Tensile Stress ◽  
Strain Curve ◽  
Tensile Tests ◽  
Tensile Failure ◽  
Tensile Behaviour ◽  
Masonry Structures ◽  
Stress Strain ◽  
Flexural Tensile Strength ◽  
Cracking Pattern ◽  
Direct Tensile

This paper presents the results of direct tensile tests performed on six different FRCM (fabric reinforced cementitious matrix) strengthening systems used for masonry structures. The emphasis was placed on the determination of the mechanical parameters of each tested system and a comparison of their tensile behaviour in terms of first crack stress, ultimate stress, ultimate strain, cracking pattern, failure mode and idealised tensile stress-strain curve. In addition to the basic mechanical tensile parameters, accidental load eccentricities, matrix tensile strengths, and matrix modules of elasticity were estimated. The results of the tests showed that the tensile behaviour of FRCM composites strongly depends on the parameters of the constituent materials (matrix and fabric). In the tests, tensile failure of reinforcement and fibre slippage within the matrix were observed. The presented research showed that the accidental eccentricities did not substantially affect the obtained results and that the more slender the specimen used, the more consistent the obtained results. The analysis based on a rule of mixtures showed that the direct tensile to flexural tensile strength ratio of the matrixes used in the test was 0.2 to 0.4. Finally, the tensile stress–strain relationship for the tested FRCMs was idealised by a bi- or tri-linear curve.

scholarly journals Size effect on the methodology with cylinder specimens for FRP-to-concrete debonding analysis

2021 ◽  
Vol 14 (3) ◽  
Author(s):  
Luana Ferreira Borges ◽  
Antonio Carlos dos Santos
Keyword(s):  
Size Effect ◽  
Failure Modes ◽  
Tensile Force ◽  
Size Variation ◽  
Concrete Specimen ◽  
Three Dimensions ◽  
Tensile Failure ◽  
Interface Failure ◽  
Reinforced Polymer ◽  
Direct Tensile

Abstract This is a study about the size effect on the methodology with concrete cylinder specimens for analysis of the debonding phenomenon at the interface between concrete and carbon fiber reinforced polymer (FRP). The influence of the concrete specimen size variation is analyzed by maintaining the same geometry in adhered FRP. Direct tensile experiments were performed with three dimensions of cylindrical concrete specimens (diameter × height) for analysis of size effect: 50 mm × 100 mm, 100 mm × 200 mm, and 150 mm × 300 mm. Ten different geometries of the composite material were tested. Two failure modes were observed in the experiments: debonding between the two materials and tensile failure in concrete specimens. In experiments with interface failure, the size of concrete specimens has no significant influence on maximum force, shear stress to peak, and stiffness in debonding between concrete and FRP. However, the use of smaller specimens for analysis of interface collapse is limited because the concrete reaches its normal stress capacity with a lower tensile force, and therefore, the failure often occurs in the concrete.

Experimental Research on Failure Modes of Specimen Containing Non-Coplanar Joints

2013 ◽  
Vol 779-780 ◽  
pp. 332-336
Author(s):  
Ping Cao ◽  
Wen Cheng Fan ◽  
Ke Zhang
Keyword(s):  
Shear Strength ◽  
Failure Mode ◽  
Failure Modes ◽  
Cement Mortar ◽  
Failure Process ◽  
Jointed Rock ◽  
Important Relationship ◽  
Initial Setting ◽  
Series Of Experiments ◽  
Dip Angle

To study the failure mechanism and failure mode of jointed rock under compressive-shear, many rock-like material specimens containing non-coplanar joints were made and a series of experiments were carried out. In the experiments, mica sheets were used as joint fillings, cement mortar was selected as rock-like material. Joints were made by inserting the mica sheet in cement mortar before initial setting. Mica sheets were left down as joint fillings. The results of experiments show that the dip angles of major joint have important influence on the failure mode of specimens. And the emerging position of wing cracks which exist in the prophase of specimens failure process changes with the dip angle. The shear strength of specimens has an important relationship with the dip angle of major joints. The smallest shear strength happens in the specimen with a joint angle of 15°, while the biggest value happens in 60°.

Experimental Investigation on the Mechanical Behavior of Polyurethane PICCs after Long-Term Conservation in in Vivo-Like Conditions

2017 ◽  
Vol 18 (6) ◽  
pp. 522-529 ◽  
Author(s):  
Francesca Di Puccio ◽  
Giuseppe Gallone ◽  
Andrea Baù ◽  
Emanuele M. Calabrò ◽  
Simona Mainardi ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Tensile Tests ◽  
Ethanol Solution ◽  
Uniaxial Tensile ◽  
Research Activity ◽  
Two Fluids ◽  
Weight Variation

Introduction In a previous paper, the authors investigated the mechanical behavior of several commercial polyurethane peripherally inserted central venous catheters (PICCs) in their ‘brand new’ condition. The present study represents a second step of the research activity and aims to investigate possible modifications of the PICC mechanical response, induced by long-term conservation in in vivo-like conditions, particularly when used to introduce oncologic drugs. Methods Eight 5 Fr single-lumen catheters from as many different vendors, were examined. Several specimens were cut from each of them and kept in a bath at 37°C for 1, 2, 3 and 6 months. Two fluids were used to simulate in vivo-like conditions, i.e. ethanol and Ringer-lactate solutions, the first being chosen in order to reproduce a typical chemical environment of oncologic drugs. The test plan included swelling analyses, uniaxial tensile tests and dynamic mechanical thermal analysis (DMTA). Results and conclusions All tested samples were chemically and mechanically stable in the studied conditions, as no significant weight variation was observed even after six months of immersion in ethanol solution. Uniaxial tensile tests confirmed such a response. For each PICC, very similar curves were obtained from samples tested after different immersion durations in the two fluid solutions, particularly for strains lower than 10%.

Study of Mechanical Behavior of Concrete in Direct Tensile Fiber Chips

2011 ◽  
Vol 146 ◽  
pp. 64-73
Author(s):  
Youcef Bouafia ◽  
M. Said Kachi ◽  
Djamel Atlaoui ◽  
Said Djebali
Keyword(s):  
Mechanical Behavior ◽  
Fiber Length ◽  
Volume Fraction ◽  
Tensile Tests ◽  
Cement Matrix ◽  
Direct Tension ◽  
Cracking Behavior ◽  
Machine Type ◽  
Direct Tensile ◽  
Local Fiber

In this experimental study, we are interested in local fiber wavy chips derived from waste machining steel parts. This work has focused on studying the mechanical behavior of reinforced concrete, with this type of fiber, in direct tensile. Direct tensile tests were carried out on samples in free weights section and square (100x100) mm2. This test involves the design and the implementation of special mounting specimens on the tensile machine type Ibertest. Five (05) fibers percentages were retained in (W = 0.5%. W = 0.8%, W = 1%, W = 1.2%, W = 1.5% with W: volume fraction of added fiber) and two (02) concrete witness whose report on gravel sand is equal to: S / G = 0.8 and S / G = 1. The fibers have been characterized to the strength and tear by the tensile test. The interest lies in optimizing the fiber length and the number of undulations to use in a cement matrix, which will improve the mechanical properties especially tensile strength and post-cracking behavior. The comparison of different results obtained in direct tension on different percentages of fiber, as well as two reports showed that the fibers have conferred a significant ductility to the material after cracking of concrete for different percentages of fiber and a strength for improving the S / G = 0.8.

scholarly journals MECHANICAL BEHAVIOR AND CATENARY ACTION OF RESTRAINED STEEL BEAM UNDER FIRE

2021 ◽  
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Failure Modes ◽  
Tensile Tests ◽  
Steel Beams ◽  
Steel Beam ◽  
Catenary Action ◽  
Standard Fire ◽  
Loading Ratio ◽  
Fire Experiments

To investigate the mechanical behavior and catenary action of restrained steel beam under fire, experiments were performed on five H-section restrained steel beams exposed to ISO-834 standard fire. At first, mechanical property tensile tests were performed on 3 room-temperature specimens and 8 high-temperature specimens, and variation laws of the material properties of steel materials with temperature rising were investigated by the high-temperature steady-state tests. Through the fire experiments, the temperature data, mid-span deflections and failure modes of all specimens were obtained. The experimental results show that: (1) a restrained steel beam is prone to in-plane buckling failure under fire; (2) the loading ratio n and axial restraint stiffness Kx have great influences on the catenary action of restrained steel beam under fire; (3) when the loading ratio n is constant, the greater the axial restraint stiffness Kx, the later the catenary action occurs; when the axial restraint stiffness Kx is constant, the greater the loading ratio n, the earlier the catenary action occurs.

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