scholarly journals Experimental Study on the Difference of Shale Mechanical Properties

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Qi Liu ◽  
Bing Liang ◽  
Weiji Sun ◽  
Hang Zhao
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Wave Velocity ◽  
Poisson’S Ratio ◽  
Failure Modes ◽  
High Stress ◽  
Poisson's Ratio ◽  
Bedding Angle ◽  
The Difference

This paper studies the anisotropic characteristics of shale and the difference in mechanical performance between deep shale and outcrop shale. The outcrop shale was collected from the Shuanghe section in Changning County, southern Sichuan, and the deep shale was collected from the Wells Yi201 and Lu202. Study their basic mechanical parameters, failure modes, and wave velocity responses through laboratory tests. Research shows that with the increase of bedding angle, the deformation mode has the trend from elastic deformation to plastic deformation in high-stress state. When the bedding angles are 0°, 30°, and 45°, the weak bedding surface plays a leading role in the formation of the failure surface trend. As the bedding angle increases to 60° and 90°, its influence is weakened. The tensile strength, elastic modulus, and wave velocity decrease with the increase of bedding angle. The compressive strength and Poisson’s ratio have the law of U-type change, there are higher values at 0° and 90°, and the lowest values are at 30°. The brittleness index first increases and then decreases with the increase of the bedding angle. The tensile strength and Poisson’s ratio of outcrop shale and deep shale are close, but the compressive strength of deep shale is only 1/3 of outcrop shale, the elastic modulus is only 3/4 of outcrop shale, and the failure of deep shale is accompanied by instability failure.

THE EFFECT OF POROSITY ON ENGINEERING PROPERTIES OF VESICULAR AMYGDALOIDAL BASALTS

2021 ◽  
Vol 5 (11) ◽  
Author(s):  
P .S.K.Murthy ◽  
Sachin Gupta ◽  
Dhirendra Kumar ◽  
Mahabir Dixit
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Modulus Of Elasticity ◽  
Poisson’S Ratio ◽  
Central India ◽  
Poisson's Ratio ◽  
Engineering Properties ◽  
Secondary Minerals

The interconnection of vesicles in basaltic flows greatly affects the engineering properties such as uniaxial compressive strength, modulus of elasticity, Poisson’s ratio, tensile strength and sonic velocities. Sometimes these vesicles are filled with secondary minerals such as quartz/olivine/calcite form as amygdules (which are impermeable). In the present study, to understand effect of porosity, vesicular and amygdular basaltic flows collected from central and west-central India were investigated for these engineering properties and correlated with apparent porosity of core samples. It is observed that a good level of correlation is obtained for uniaxial compressive strength (UCS), elastic modulus (E) and Poisson’s ratio in vesicular basalts when porosity >8-10%. In case of Brazilian strengths a linearly downward trend is observed with the increase in porosity values. And, no significant correlation is observed for waves’ velocities in both variants of basalts.

scholarly journals Experimental Research on the Mechanical Characteristics and the Failure Mechanism of Coal-Rock Composite under Uniaxial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ke Yang ◽  
Zhen Wei ◽  
Xiaolou Chi ◽  
Yonggang Zhang ◽  
Litong Dou ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Poisson’S Ratio ◽  
Mechanical Characteristics ◽  
Poisson's Ratio ◽  
Energy Value ◽  
Coal Rock

Due to the influence of the component structure and combination modes, the mechanical characteristics and failure modes of the coal-rock composite show different characteristics from the monomer. In order to explore the effect of different coal-rock ratios on the deformation and the failure law of the combined sample, the RMT rock mechanics test system and acoustic emission real-time monitoring system are adopted to carry out uniaxial compression tests on coal, sandstone, and three kinds of combined samples. The evolution rules of the mechanical parameters of the combined samples, such as the uniaxial compressive strength, elastic modulus, and Poisson’s ratio, are obtained. The expansion and failure deformation characteristics of the combined sample are analyzed. Furthermore, the evolution laws of the fractal and acoustic emission signals are combined to reveal the crack propagation and failure mechanism of the combined samples. The results show that the compressive strength and elastic modulus of the combined sample increase with the decrease of the coal-rock ratios, and Poisson’s ratio decreases with the decrease of the coal-rock ratios. The strain softening weakens at the postpeak stage, which shows an apparent brittle failure. The combined sample of coal and sandstone has different degrees of damages under load. The coal is first damaged with a high degree of breakage, with obvious tensile failure. The acoustic emission energy value presents different stage characteristics with increasing load. Crackling sound occurs in the destroy section before the sample reaches the peak, along with small coal block ejection and the partial destruction. The energy value fluctuates violently, with the appearance of several peaks. At the postpeak stage, the coal samples expand rapidly with a loud crackling sound in the destroy section, and the energy value increases dramatically. The crack propagation induces the damage in the sandstone; when the energy reaches the limit value, the instantaneous release of elastic energy leads to the overall structural instability.

scholarly journals Experimental Study on the Influence of Moisture Content on the Mechanical Properties of Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mingxing Gao ◽  
Yongli Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Moisture Content ◽  
Uniaxial Compressive Strength ◽  
Poisson’S Ratio ◽  
Triaxial Compression ◽  
Test System ◽  
Poisson's Ratio ◽  
Compression Tests

Water injection in coal seams will lead to the increase of moisture content in coal, which plays an essential role in the physical and mechanical properties of coal. In order to study the influence of moisture content on the mechanical properties of soft media, the forming pressure (20 MPa) and particle size ratio (0-1 mm (50%), 1-2 mm (25%), and 2-3 mm (25%)) during briquette preparation were firstly determined in this paper. Briquettes with different moisture contents (3%, 6%, 9%, 12%, and 15%) were prepared by using self-developed briquettes. Uniaxial and triaxial compression tests were carried out using the RMT-150C rock mechanics test system. The results show that the uniaxial compressive strength and elastic modulus of briquette samples increase first and then decrease with the increase of briquette water, while Poisson’s ratio decreases first and then increases with the increase of briquette water. When the moisture content is around 9%, the maximum uniaxial compressive strength is 0.866 MPa, the maximum elastic modulus is 1.385 GPa, and Poisson’s ratio is at the minimum of 0.259. The compressive strength of briquettes increases with the increase of confining pressure. With the increase of moisture content, the cohesion and internal friction angle of briquettes first increased and then decreased.

scholarly journals Elastic Mechanical Properties of 45S5-Based Bioactive Glass–Ceramic Scaffolds

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3244 ◽  
Author(s):  
Francesco Baino ◽  
Elisa Fiume
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Shear Modulus ◽  
Glass Ceramic ◽  
Poisson’S Ratio ◽  
Mechanical Performance ◽  
Poisson's Ratio ◽  
Shear Moduli ◽  
Bioactive Scaffolds

Porosity is recognized to play a key role in dictating the functional properties of bioactive scaffolds, especially the mechanical performance of the material. The mechanical suitability of brittle ceramic and glass scaffolds for bone tissue engineering applications is usually evaluated on the basis of the compressive strength alone, which is relatively easy to assess. This work aims to investigate the porosity dependence of the elastic properties of silicate scaffolds based on the 45S5 composition. Highly porous glass–ceramic foams were fabricated by the sponge replica method and their elastic modulus, shear modulus, and Poisson’s ratio were experimentally determined by the impulse excitation technique; furthermore, the failure strength was quantified by compressive tests. As the total fractional porosity increased from 0.52 to 0.86, the elastic and shear moduli decreased from 16.5 to 1.2 GPa and from 6.5 to 0.43 GPa, respectively; the compressive strength was also found to decrease from 3.4 to 0.58 MPa, whereas the Poisson’s ratio increased from 0.2692 to 0.3953. The porosity dependences of elastic modulus, shear modulus and compressive strength obeys power-law models, whereas the relationship between Poisson’s ratio and porosity can be described by a linear approximation. These relations can be useful to optimize the design and fabrication of porous biomaterials as well as to predict the mechanical properties of the scaffolds.

scholarly journals Experimental Development Process of a New Cement and Gypsum-Cemented Similar Material considering the Effect of Moisture

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Qi Liu ◽  
Shaojie Chen ◽  
Shuai Wang ◽  
Jing Chai ◽  
Dingding Zhang
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Moisture Content ◽  
Uniaxial Compressive Strength ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Mass Ratio ◽  
Similar Material ◽  
Residual Moisture ◽  
Similar Materials

A new type of similar material considering water characteristics is developed through orthogonal experiments. The similar material is composed of river sand, barite powder, cement, gypsum, and water. We determine the best test development process. First, the proportion test scheme is designed based on the orthogonal test. Then, the effects of the moisture content, mass ratio of aggregate to binder and other components on the density, uniaxial compressive strength, elastic model, and Poisson’s ratio of similar materials are analyzed by range analysis. Finally, the multiple linear regression equation between the parameters and the composition of similar materials is obtained, and the optimal composition ratio is determined according to the relationship between the test’s influencing factors and the mechanical properties of similar materials. The results show that the selected raw materials and their proportioning method are feasible. The content of barite powder plays a major role in controlling the density and Poisson’s ratio of similar materials. The mass ratio of aggregate to binder is the main factor that affects the uniaxial compressive strength and elastic modulus of similar materials, while the moisture content has the second largest effect on the density, uniaxial compressive strength, elastic modulus, and Poisson’s ratio of similar materials. When the residual moisture content increased from 0 to 4%, the uniaxial compressive strength and elastic modulus of similar materials decrease by 49.5% and 53.3%, respectively, and Poisson’s ratio increases by 54.8%. Determining the residual moisture content that matches the design of similar material model tests is critical to improving the test accuracy and provides a reference to prepare similar materials with different requirements.

scholarly journals Study of Strength and Deformation Evolution in Raw and Briquette Coal Samples under Uniaxial Compression via Monitoring Their Acoustic Emission Characteristics

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Han Meng ◽  
Yuzhong Yang ◽  
Liyun Wu ◽  
Fei Wang ◽  
Lei Peng
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Brittle Failure ◽  
Poisson’S Ratio ◽  
Cement Content ◽  
Poisson's Ratio ◽  
Ae Signal

Briquette coals with different cement contents are frequently used to study the coal body’s properties. In this study, the deformation and strength of briquette coal samples with 0, 5, 10, and 20% cement contents were experimentally and theoretically investigated using the acoustic emission (AE) characteristics monitored during the uniaxial compression tests. The results show that the uniaxial compression process of raw coal and briquette coal samples can be subdivided into compaction, elastic, plastic (yield), and brittle failure stages. With an increase in cement content, briquette coal samples undergo the elastic and plastic stages, and their postpeak stress drop rate gradually grows, and their plastic deformation is followed by brittle failure. The uniaxial compressive strength and elastic modulus of briquette coal samples show a linearly increasing relationship with cement content, while their Poisson’s ratio decreases gradually. During the uniaxial compression, raw coal and briquette coal samples produce the AE signals. The overall AE signal of briquette coal samples is relatively low, and there are no obvious AE events in raw coal samples. The uniaxial compressive strength, elastic modulus, and Poisson’s ratio of briquette coal samples with a 20% cement content and their AE signal cumulative amplitude, count, and energy values are very close to the corresponding parameters of raw coal samples. Therefore, they can be used for simulating raw coal samples in laboratory tests.

scholarly journals Experimental investigation on engineering properties of lightweight foamed concrete (LFC) with coconut fiber addition

2018 ◽  
Vol 250 ◽  
pp. 05005
Author(s):  
Nabihah Mohd Zamzani ◽  
Azree Othuman Mydin ◽  
Abdul Naser Abdul Ghani
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Poisson’S Ratio ◽  
Splitting Tensile Strength ◽  
Poisson's Ratio ◽  
Engineering Properties ◽  
Coconut Fiber ◽  
Foamed Concrete ◽  
Coconut Fibre

In the last few years, there is emerging attention in using Lightweight Foamed Concrete (LFC) as a lightweight non-structural and semi-structural element in buildings to take advantage of its excellent insulation properties. Though, LFC has been noticed to have some disadvantages: considerable brittleness; results in low compressive and flexural strength, poor fracture toughness, poor resistance to crack propagation and low impact strength. Coconut fibre obtained from coconut husk, belonging to the family of palm fibres, is agricultural waste products obtained in the processing of coconut oil. In Malaysia, they are available in large quantities. Coconut fibre is extracted from the outer shell of a coconut. There are many general advantages of coconut fibres e.g. they are moth-proof, resistant to fungi and rot, provide excellent insulation against temperature and sound, not easily combustible, flame-retardant, unaffected by moisture and dampness, tough and durable, resilient, springs back to shape even after constant use, totally static free and easy to clean. Hence this study is intended to look into the potential of coconut fiber in enhancing the engineering properties of LFC. There are 5 engineering properties will be focused in this study which are flexural strength, splitting tensile strength, compressive strength, Poisson’s ratio and Poisson’s ratio toughness. Three densities of LFC of 800 kg/m3, 1100 kg/m3 and 1400 kg/m3 were cast and tested. The ratio of cement, sand and water used in this study was 1:1.5:0.49. Coconut fibers were used as additives at 0.12%, 0.24%, 0.36%, 0.48% and 0.60% by volume of the total mix. Test results indicated that the engineering properties of LFC strengthen with coconut fiber had increased soundly. Coconut fiber inclusion changes the post-peak response at the load-deflection curves for the samples, which modifies the failure mode and enhance the flexural strength, compressive strength and splitting tensile strength.

scholarly journals Mechanical Properties and Conversion Relations of Strength Indexes for Stone/Sand-Lightweight Aggregate Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Xianggang Zhang ◽  
Dapeng Deng ◽  
Jianhui Yang
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Lightweight Aggregate ◽  
Poisson's Ratio ◽  
Lightweight Aggregate Concrete ◽  
Replacement Rate ◽  
River Sand ◽  
Aggregate Concrete ◽  
Axial Compressive Strength

This is a study of the basic mechanical properties of specified density shale aggregate concrete, which is based on different replacement rates in stone-lightweight aggregate concrete (stone-LAC) and sand-lightweight aggregate concrete (sand-LAC). They were prepared by replacing the ceramsite and pottery sand with stone and river sand, respectively. Many tests were performed regarding the basic mechanical property indexes, including tests of cube compressive strength, axial compressive strength, splitting tensile strength, flexural strength, elastic modulus and Poisson’s ratio. The failure modes of specified density shale aggregate concrete were obtained. The effects of replacement rates on the mechanical property indexes of specified density shale aggregate concrete were analyzed. Calculation models were implemented for elastic modulus, for the conversion relations between the axial compressive strength and the cube compressive strength, and for the relations between the tension-compression ratio and Poisson’s ratio. It was shown that when the replacement rate of stone or river sand increased from 0% to 100%, the cube compressive strength of stone-LAC and sand-LAC increased, respectively, by 55% and 25%, the axial compressive strength increased, respectively, by 91% and 72%, splitting tensile strength increased, respectively, by 99% and 44%, and the flexural strength increased, respectively, by 46% and 26%. Similarly, the elastic modulus of stone-LAC and sand-LAC increased, respectively, by 16% and 30%. However, Poisson’s ratio for stone-LAC decreased first and then increased, eventually increased by 11%; Poisson’s ratio for sand-LAC only reduced gradually, eventually reduced by 67%. After introducing the influence parameter for the replacement rate, the established calculation models become simple and practical, and the calculation accuracies are favorable.

scholarly journals Relationship Between Mode I Fracture Toughness and Strength Parameters of Brittle and Plastic Coal and the Fracture Process

2021 ◽  
Author(s):  
Zhe Ma ◽  
Jing Chai ◽  
Jianfeng Yang ◽  
Dingding Zhang ◽  
Yongliang Liu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Plastic Zone ◽  
Crack Growth ◽  
Fracture Process ◽  
Peak Load ◽  
Poisson's Ratio ◽  
Mode I ◽  
Strength Parameters

Abstract Underground roadway excavation will form a plastic circle within the surrounding rock. The brittleness and plasticity of coal at different positions relative to the plastic circle are significantly different. Through drilling and sampling of the roadway roof, the KIC and strength parameters of coal with different brittle and plastic at different positions of roadway plastic circle were tested. Coal samples were collected at borehole depths of 0.7 m, 2.5 m, and 4.4 m, which are respectively located in the plastic circle, on the edge of the plastic circle, and outside of the plastic circle. The KIC and strength parameters of coal at different positions relative to the plastic zone are quite different. The KIC of coal at 0.7 m, 2.5 m, and 4.4 m borehole depth is 0.2436 MPa, 0.1736 MPa, and 0.1504 MPa, respectively. With increasing borehole depth, the compressive strength of coal increases, and the tensile strength decreases. For specimens with high compressive strength, the elastic modulus is relatively large, but Poisson ratio is relatively small. The linear fitting of KIC and strength parameters of coal shows that the KIC of coal negatively correlates with compressive strength and elastic modulus; the KIC of coal positively correlates with tensile strength and Poisson's ratio. Compared with the compressive strength, the tensile strength of coal has a stronger influence on the KIC and cracks can more easily expand with increasing tensile stress. Compared with the elastic modulus, Poisson's ratio has a stringer influence on crack growth and has a stronger correlation with the KIC of coal. And the relationship between the brittle index and the KIC is studied. The deeper the borehole is, the greater the brittleness index of coal is. There is a linear relationship between brittleness and KIC. KIC can be characterized by coal brittleness. Digital image correlation (DIC) was used to analyze the mode I crack growth characteristics and nonlinear failure process of semicircular three-point bending specimens. The accurate crack initiation point (PS) and the critical crack tip opening displacement (W0) of different brittle plastic coals are obtained. Compared with experimental results and numerical simulation, the method for calculating the W0 in this paper is more accurate. By using this method defined in this paper, the W0 of coal at 0.7 m, 2.5 m, and 4.4 m borehole depth are 0.0149 mm, 0.0138 mm, and 0.0115 mm, respectively. Mode I cracks in coal with stronger brittleness outside the plastic zone are easier to propagate. The non-linear fracture process of coal with stronger plasticity is more significant at shallow depths, and the load at the PS point at 0.7 m borehole depth is only 64.05% of the peak load. With increasing borehole depth, the more brittle the coal is, the closer it is to elastic failure. The load at the PS point of coal at 4.4 m borehole depth is 98.07% of the peak load, proving the importance of nonlinear fracture behavior analysis of coal. This study is significant to analyzing the crack propagation behavior of coal at different positions relative to the plastic circle of roadway and to analyzing the mechanism and features of different forms of roadway failures like roof fall and rock burst.

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