scholarly journals A Study of the Relationship between the Stress State and Failure Mode of Concrete Specimens

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Xinyu Liang ◽  
Faning Dang
Keyword(s):  
Internal Stress ◽  
Failure Mode ◽  
Shear Failure ◽  
Ambient Pressure ◽  
Failure Process ◽  
Failure Surface ◽  
The State ◽  
Tensile Failure ◽  
Aspect Ratios ◽  
The Relationship

An investigation of concrete specimen’s strength and its changing mechanism based on numerical simulation of the failure process of axis-stressed concrete specimens with different aspect ratios was described. The state of internal stress and growth of crack of axis-stressed concrete specimens, as well as the changing mechanism of specimen strength under different ambient pressure values, were investigated. The results revealed that specimen strength and failure surface decreased as the aspect ratio is increased. The specimen strength is dependent on the state of internal stress and decreased with decreasing ambient pressure. Additionally, the failure mode shifted from shear failure to tensile failure gradually.

scholarly journals Failure Process Simulation of Interlayered Rocks under Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Chi Yao ◽  
Sizhi Zeng ◽  
Jianhua Yang
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Strength Criterion ◽  
Tensile Failure ◽  
Strength Anisotropy ◽  
Rigid Block ◽  
Bedding Planes ◽  
Typical Experiment ◽  
Confining Pressures ◽  
Spring Method

Anisotropy in strength and deformation of rock mass induced by bedding planes and interlayered structures is a vital problem in rock mechanics and rock engineering. The modified rigid block spring method (RBSM), initially proposed for modeling of isotropic rock, is extended to study the failure process of interlayered rocks under compression with different confining pressures. The modified rigid block spring method is used to simulate the initiation and propagation of microcracks. The Mohr–Coulomb criterion is employed to determine shear failure events and the tensile strength criterion for tensile failure events. Rock materials are replaced by an assembly of Voronoi-based polygonal blocks. To explicitly simulate structural planes and for automatic mesh generation, a multistep point insertion procedure is proposed. A typical experiment on interlayered rocks in literature is simulated using the proposed model. Effects of the orientation of bedding planes with regard to the loading direction on the failure mechanism and strength anisotropy are emphasized. Results indicate that the modified RBSM model succeeds in capturing main failure mechanisms and strength anisotropy induced by interlayered structures and different confining pressures.

scholarly journals Experimental Study on Bending Performance of Composite Sandwich Panel with New Mixed Core

2019 ◽  
Vol 275 ◽  
pp. 02018
Author(s):  
Jing Zhang ◽  
Xiamin Hu ◽  
Wan Hong ◽  
Bing Zhang ◽  
Chengli Zhang
Keyword(s):  
Experimental Investigation ◽  
Polyurethane Foam ◽  
Failure Mode ◽  
Shear Failure ◽  
Sandwich Panels ◽  
Tensile Failure ◽  
Bending Test ◽  
Bending Performance ◽  
Composite Sandwich Panels ◽  
Composite Sandwich

This paper presents an experimental investigation of bending performance of composite sandwich panels with new mixed core, sandwich panels were tested by four-point bending test. Parametric study was conducted to investigate the influence of different core materials on the failure mode, ultimate bearing capacity, stiffness and ductility of composite sandwich panels. The results of the experimental investigation showed that the mixed core can change the failure mode of sandwich panels. The failure mode of wooden panels is characterized by tensile failure of bottom wood, and the failure mode of composite sandwich panels with wood core is that the surface layer and core are stripped and the webs are damaged by shear, while the failure mode of composite sandwich panels with wood and polyurethane foam mixed core is the shear failure of the web. Composite sandwich panels with GFRP-wood-polyurethane foam core have better bending performance and can effectively reduce the weight of panels.

Laboratory Model Test Study of Tunnel Anchor

2014 ◽  
Vol 1065-1069 ◽  
pp. 333-336
Author(s):  
Bing Shen ◽  
Sai Qiong Long ◽  
Jun Chen ◽  
Yong Bing Li
Keyword(s):  
Model Test ◽  
Shear Failure ◽  
Failure Surface ◽  
Tensile Failure ◽  
Laboratory Model ◽  
Pull Out ◽  
Test Study ◽  
Cable Force ◽  
Anchor Design ◽  
Laboratory Model Test

A laboratory model test of tunnel anchor was conducted to investigate its pullout mechanism and bearing capacity. Surface and rock deformation, strain and stress were measured during the entire model test process. The results show that: under pull out load, tensile failure first occurs in top surface rock near the anchor, then shear failure occurs in anchor-rock interface and rock around the anchor. The failure surface is inverted cone from the anchor bottom. Under 50 times design cable force tunnel rock is in elastic stage, suggesting that current tunnel anchor design is quite conservative and can be further optimized.

scholarly journals Experimental Study of the Mechanical Characteristics of a Rock-Like Material Containing a Preexisting Fissure under Loading and Unloading Triaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Taoli Xiao ◽  
Mei Huang ◽  
Min Gao
Keyword(s):  
Experimental Study ◽  
Failure Mode ◽  
Mechanical Characteristics ◽  
Failure Modes ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Tensile Failure ◽  
Underground Engineering ◽  
Inclination Angles ◽  
Loading And Unloading

An experimental study of a rock-like material containing a preexisting fissure subjected to loading and unloading triaxial compression is carried out, and the results show that the mechanical characteristics of the rock-like specimen depend heavily on the loading paths and the inclination of the fissure. The triaxial loading experiment results show that the failure strength linearly increases, while the residual strength linearly decreases with increasing inclination. Furthermore, specimens subjected to triaxial compression show an “X”-type shear failure mode. The triaxial unloading compression experimental results show that specimens with different inclination angles have various failure modes. Specimens with gentle inclinations show a tensile-shear mix failure mode, specimens with middle inclinations show a shear-sliding failure mode, and specimens with steep inclinations show a tensile failure mode. These findings can be used to forecast excavation-induced instabilities in deep underground engineering rock structures.

scholarly journals Numerical Studies on the Failure Process of Heterogeneous Rock Material with Preexisting Fracture under Uniaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qi Zhang ◽  
Dan Ma ◽  
Jiangfeng Liu ◽  
Kai Zhang ◽  
Zhiqiang Fan
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Damage Model ◽  
Rock Material ◽  
Tensile Failure ◽  
Underground Engineering ◽  
Intact Specimen ◽  
Numerical Studies ◽  
Heterogeneous Rock ◽  
Reduced Parameters

It is of vital importance to understand the failure processes of the heterogeneous rock material with different kinds of preexisting fractures in underground engineering. A damage model was introduced to describe the initiation and propagation behaviors of the fractures in rock. Reduced parameters were applied in this work because the microcracks in the rock were neglected. Then, the numerical model was validated through comparing the simulation results with the laboratory observations. Finally, a number of numerical uniaxial compressive tests were performed on heterogeneous rock specimens with preexisting fracture, and the influence of the heterogeneity of the rock and the angle and length of the preexisting fractures was fully discussed. The results showed that the brittleness of the rock increased with the increase of the homogeneity index, and tensile failure was the main failure form for relatively heterogeneous rock, whilst shear failure was the main failure form for relatively homogeneous rock. The uniaxial compressive strengths of the specimens with the angles of 0, 30, 45, and 60 of the preexisting fracture dropped 62.7%, 54.7%, 46.6%, and 38.2% compared with that of the intact specimen; the tensile cracks were more difficult to form, and the required load was increasing with the increase of the angle of the preexisting fracture; besides, antiwing cracks were difficult to form than wing cracks because the tensile stress in wing cracks’ area was greater than that in antiwing cracks’ area. The uniaxial compressive strengths of the specimens with the lengths of 20 mm, 25 mm, 30 mm, and 35 mm of preexisting fracture dropped 38.6%, 46.6%, 53.4%, and 56.6% compared with that of the intact specimen, and the damage conditions of the samples with different lengths of preexisting fracture were similar.

scholarly journals THE MODEL OF BRITTLE MATRIX COMPOSITES FOR DISTRIBUTION OF STEEL FIBRES / PLIENINIŲ FIBRŲ PASISKIRSTYMO KOMPOZITUOSE SU TRAPIOMIS MATRICOMIS MODELIS

2012 ◽  
Vol 18 (1) ◽  
pp. 145-150 ◽  
Author(s):  
Wiesława Głodkowska ◽  
Janusz Kobaka
Keyword(s):  
Steel Fibre ◽  
Experimental Tests ◽  
Failure Surface ◽  
Tensile Failure ◽  
Fine Aggregate ◽  
Matrix Composites ◽  
Fibre Distribution ◽  
Steel Fibres ◽  
Brittle Matrix Composites ◽  
The Relationship

The paper deals with the distribution of steel fibres in the mineral composite of fine aggregate. The authors have proposed the distribution of steel fibres in a composite space model based on statistical grounds. The model provides for the randomness of fibre distribution in composite space in accordance with the adopted probability distribution. The developed model has been experimentally verified. The results concerning the distribution of steel fibres in mineral com- posite have been obtained from the statistical model and compared with those of the model frequently applied by other au- thors on the basis of geometric grounds. Good compatibility of steel fibre distribution for a description of both models has been ascertained. As the amount of fibres influences the strength of composite tensile, the relationship between the above introduced feature and the quantity of fibres in the cross-section located nearby tensile failure surface has been developed with reference to the experimental tests. Santrauka Straipsnyje analizuojamas plieninių fibrų pasiskirstymas kompozite su mineraliniais užpildais. Autoriai pasiūlė plieninių fibrų pasiskirstymo kompozite modelį, grįstą statistine analize. Fibrų pasiskirstymas matricoje nagrinėjamas kaip atsitiktinis dydis, pasiskirstęs pagal tikimybinį skirstinį. Modelis yra eksperimentiškai patikrintas: plieninių fibrų pasiskirstymas kompozito matricoje pagal siūlomą statistinį modelį buvo palygintas su kitų autorių tyrimų rezultatais, taikant modelius, grįstus geometriniais pagrindais. Gauti rezultatai sutampa gerai. Kadangi plieninių fibrų kiekis turi įtakos kompozito tempiamajam stipriui, pateikta eksperimentiniais tyrimais pagrįsta priklausomybė tarp fibrų kiekio ir kompozito tempiamojo stiprio.

scholarly journals Dynamic Tensile Strength of Dry and Saturated Hard Coal under Impact Loading

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1273
Author(s):  
Xianlei Zhu ◽  
Qing Li ◽  
Guihua Wei ◽  
Shizheng Fang
Keyword(s):  
Tensile Strength ◽  
High Speed ◽  
Shear Failure ◽  
Split Hopkinson Pressure Bar ◽  
Failure Process ◽  
Tensile Failure ◽  
Hard Coal ◽  
Control Group ◽  
Hopkinson Pressure Bar ◽  
Brazilian Disk

To evaluate the influence of water content on the hard coal dynamic behavior, the dynamic tensile properties of saturated coal Brazilian disk (BD) samples were studied using a split Hopkinson pressure bar system, and dry samples were also tested as a control group. In the range of impact speeds studied, the tensile strength of the saturated coal is lower than that of the dry specimen. A synchronized triggering high-speed camera was used to monitor the deformation and failure process of dry and saturated coal samples, allowing analysis of the failure stages and mechanism of dynamic BD test, the broken mode was classified into three types, which can be classified into unilateral tensile failure, bilateral or multilateral tensile failure, and shear failure. Finally, fragments smaller than 5 mm in diameter were statistically analyzed. There is less debris in range of 0–5.0 mm for the saturated coal sample than for the dry coal. This study provides some information about the dynamic response of the hard coal for the relevant practical engineering.

The Bearing Capacity Character of Enlarged Base Shallow Foundation under Uplift Load

2011 ◽  
Vol 243-249 ◽  
pp. 2151-2156 ◽  
Author(s):  
Xian Long Lu ◽  
Qiang Cui
Keyword(s):  
Shear Failure ◽  
Limit Equilibrium ◽  
Failure Process ◽  
Field Tests ◽  
Failure Surface ◽  
Theory Model ◽  
Shallow Foundation ◽  
Deformation And Failure ◽  
Uplift Load ◽  
Uplift Resistance

By theory analysis and field tests, failure model of soil around foundation and ultimate uplift resistance of enlarged bass shallow foundation were analyzed. The results showed that the deformation and failure process of soil around foundation under uplift load undergone three phases: 1) soil upon enlarged base compressed, 2) appearance and extension of plastic zone of soil around foundation, and 3) soil around foundation general shear failure. With the combination of the Limit Equilibrium Method, and Sliding Curve Theory, a simplified theory model to calculate net ultimate uplift resistance of shallow foundation assuming cir failure surface under uplift load was established. Then three examples were calculated by this method and the good agreement between theory calculation solution and experimental results validated the rationality of the model. The study in this paper provided an important theoretical support and brand-new idea on calculation method of uplift capacity of foundation with enlarged base and failure surface characteristics determination of soil around foundation.

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.

scholarly journals Investigation on Pore-Fracture of Coal and Its Influence Mechanism on Tensile Failure Behavior of Coals with Bursting Proneness

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yutao Li ◽  
Qingwei Guo ◽  
Xunchen Liu ◽  
Yaodong Jiang ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Spatial Distribution ◽  
Failure Mode ◽  
Failure Process ◽  
Elastic Strain Energy ◽  
Tensile Failure ◽  
Failure Behavior ◽  
Secondary Fracture ◽  
Deformation And Failure ◽  
Influence Mechanism

Both computed tomography (CT) and notched semicircular bend (NSCB) tests are performed for coals with high and medium bursting proneness to extract the scientific expression of pore-fracture and its influence mechanism on the tensile failure behavior. The acoustic emission (AE) parameters in the sample during loading and failure are monitored, and the influence mechanism of pore-fracture on tensile failure behavior of coal is analyzed. The result illustrates that the spatial distribution feature of the pore-fracture in coals with high and medium bursting proneness is extremely different. The deformation and failure mode of the coals are affected by many factors, loading mode, notch depth and width, mechanical properties of matrix and minal, spatial distribution feature of pore-fracture, etc. The influence of primary pore-fracture in the coal on the extension and penetration of the secondary fracture could be divided into two types: bifurcation and promotion, which would cause different local damage in the sample and affect the final failure mode. The feature of acoustic emission parameters indicates that the deformation and failure process of a sample under loading could be divided into four stages: compaction stage, elastic deformation stage, displacement plastic growth stage, and post peak failure stage, which is the result of comprehensive action of many factors. The evolution process of secondary fracture is accompanied by the dissipation of elastic strain energy and the intensification of internal damage of coal, which reflects the failure process of coal.

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