scholarly journals Experimental Study on Coupling Influence of Temperature and Confining Pressure to Deformation and Strength Characteristics of Rock-like Material with Pre-Existing Crack

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7572
Author(s):  
Hongwei Wang ◽  
Yongyan Wang ◽  
Xi Fu
Keyword(s):  
Young’S Modulus ◽  
Failure Mode ◽  
Young's Modulus ◽  
Confining Pressure ◽  
Strength Characteristics ◽  
Peak Strain ◽  
Influence Of Temperature ◽  
Confining Pressures ◽  
Initial Cracks ◽  
Deformation And Strength Characteristics

In this paper, destructive compression tests under the coupled influence of temperatures (20–60 °C) and confining pressures (0–7 MPa) were carried out on rock-like material with pre-existing crack to explore the deformation and strength characteristics. The stress–strain curves of rock-like material under the coupled influence of temperatures and confining pressures were obtained. Meanwhile, the correlations of peak stress, peak strain, and average Young’s modulus with temperatures and confining pressures were obtained. The results of the experiments indicate that, firstly, the compressive strength decreased and the deformation increased due to the influence of pre-existing cracks; the combined effect of initial cracks, temperature, and confining pressure gave rise to a more complicated mechanism of soft rock deformation. Secondly, the deformation of rock-like material was affected by initial cracks, confining pressures, and temperatures, but the influence of temperature was lower than that of confining pressure and initial crack. The failure mode of rock-like material was brittle at the confining pressure of 0 and 1 MPa and plastic at the confining pressure of 5 and 7 MPa. The critical confining pressure value of failure mode for rock-like material was 3 MPa. Thirdly, the peak strength and peak strain of rock-like material increased with confining pressure. Temperature had less influence on the rock-like material strength and peak strain than confining pressure. Lastly, Young’s modulus decreased with temperature and confining pressure.

scholarly journals Mechanical Properties of Grouted Crushed Coal with Different Grain Size Mixtures under Triaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yuhao Jin ◽  
Lijun Han ◽  
Qingbin Meng ◽  
Suresh Sanda ◽  
Haizhi Zang ◽  
...  
Keyword(s):  
Grain Size ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Peak Strain ◽  
Compression Tests ◽  
Reinforcement Effect ◽  
Confining Pressures ◽  
Mechanical Behaviours ◽  
Ultimate Failure ◽  
Different Grain Size

To have a better understanding of the reinforcement effect on the crushed zone after grouting in coal mining extraction work, a self-designed grouting apparatus was used to study the effects of the grain size mixtures (distribution) and the stress state on the mechanical behaviours of grouted crushed coal specimens. From the various grouting tests, triaxial compression tests and scanning electron microscopy (SEM) observations of grouted specimens with different grain size mixtures, it was found that, for the same grain size mixture, the peak (σp) and residual (σr) strengths of the grouted specimens increased with an increase in confining pressure. It was found that the average slope values of the σp-σ3 curves for the grouted specimens with different grain size mixtures were all larger than those of the σr-σ3 curves. It was observed that the peak strain (εp) of the grouted specimens with different grain size mixtures increased overall with increasing confining pressure. For constant confining pressure, the peak and residual strengths both gradually increased approximately linearly as the grain size mixtures varied from small to large, but at higher confining pressures, the influence of the grain size mixture on the peak (or residual) strength increased. These mechanical behaviours of the grouted crushed coal specimens were strongly dependent on the variation in the grain size mixtures and in the confining pressure, which can be explained by the crack evolution process within the grouted specimen under triaxial compression, to a certain extent. Ultimate failure of the grouted specimen occurred just after propagation and coalescence of the cracks through the entire grouted specimen. Moreover, there were three major microscopic diffusion modes for the grouts flowing in most of the crushed coal specimens. Based on these test results, it was found that the reinforcement effect of the grouted specimen related to the splitting grouting mode (occurring in most of the large specimens) seems to be better than that of the penetrating (filling) grouting mode (in most of the small specimens).

scholarly journals Note on the influence of temperature on the rigidity of metals

1920 ◽  
Vol 97 (687) ◽  
pp. 450-455
Keyword(s):  
Temperature Effect ◽  
Young’S Modulus ◽  
Test Piece ◽  
Young's Modulus ◽  
Narrow Strip ◽  
Influence Of Temperature ◽  
Complex Constant ◽  
Fine Wire ◽  
Influence Of Temperature On ◽  
Series Of Experiments

In these ‘Proceedings,’ I described some experiments on the influence of temperature on the value of Young’s Modulus for various metals. The results showed that the more fusible the metal, the greater was the variation of the modulus with temperature, and suggested that, roughly, the decrement of the modulus for a given rise of temperature was equal to the ratio of the modulus at absolute zero to the melting temperature and a constant ( i. e. d M/ dθ = M 0 /( θ n + θ ')). Since Young’s Modulus is a complex constant, involving both rigidity and volume elasticity, it seemed worth while to examine the temperature effect on rigidity alone, and with this object in view I have recently carried out a further series of experiments on most of the metals previously tested. The apparatus used was a torsion-balance, shown diagrammatically in fig. 1. A vertical rod, A, is suspended by a long fine wire, B, and the test piece, C, in the form of a wire or narrow strip of plate, is clamped to the lower end of A, and also to the fixed support, D. The whole of this part of the balance can be immersed in a bath of fluid at any required temperature.

Study on the Deformation and Strength Characteristics of Geotechnical Grille Reinforced Sand-Gravel under Low Confining Pressure

2011 ◽  
Vol 250-253 ◽  
pp. 2632-2639
Author(s):  
Bin Xu ◽  
De Gao Zou ◽  
Jing Bi ◽  
Xian Jing Kong ◽  
Tao Gong
Keyword(s):  
Residual Strength ◽  
Large Scale ◽  
Volumetric Strain ◽  
Friction Angle ◽  
Confining Pressure ◽  
Peak Strength ◽  
Strength Characteristics ◽  
Triaxial Tests ◽  
Reinforced Sand ◽  
Deformation And Strength Characteristics

A series of large scale consolidated drained shear triaxial tests were performed on reinforced and unreinforced sand-gravel specimens, the peak strength and residual strength characteristics of reinforced and unreinforced sand-gravel specimens were compared. The results show that: the peak strength, the residual strength and cohesion of reinforced sand-gravel are higher than unreinforced specimens, and is related to the characteristics of geotechnical grille used in this study. However, adding geotechnical grille has less effect on maximum volumetric strain and internal friction angle of sand-gravel.

scholarly journals The Influence of Temperature and Atmosphere on Young's Modulus of Porous SiC.

1995 ◽  
Vol 42 (4) ◽  
pp. 474-478 ◽  
Author(s):  
Noboru Miyata ◽  
Youichi Ishida ◽  
Tatsuya Shiogai ◽  
Yohtaro Matsuo
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Influence Of Temperature ◽  
Porous Sic

scholarly journals Experimental Deformation of Opalinus Clay at Elevated Temperature and Pressure Conditions: Mechanical Properties and the Influence of Rock Fabric

2021 ◽  
Author(s):  
Valerian Schuster ◽  
Erik Rybacki ◽  
Audrey Bonnelye ◽  
Johannes Herrmann ◽  
Anja M. Schleicher ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Deformation Behavior ◽  
Water Saturation ◽  
Young's Modulus ◽  
Axial Strain ◽  
Shear Zones ◽  
Opalinus Clay ◽  
Triaxial Tests ◽  
Influence Of Water ◽  
Confining Pressures

AbstractThe mechanical behavior of the sandy facies of Opalinus Clay (OPA) was investigated in 42 triaxial tests performed on dry samples at unconsolidated, undrained conditions at confining pressures (pc) of 50–100 MPa, temperatures (T) between 25 and 200 °C and strain rates ($$\dot{\varepsilon }$$ ε ˙ ) of 1 × 10–3–5 × 10–6 s−1. Using a Paterson-type deformation apparatus, samples oriented at 0°, 45° and 90° to bedding were deformed up to about 15% axial strain. Additionally, the influence of water content, drainage condition and pre-consolidation was investigated at fixed pc–T conditions, using dry and re-saturated samples. Deformed samples display brittle to semi-brittle deformation behavior, characterized by cataclastic flow in quartz-rich sandy layers and granular flow in phyllosilicate-rich layers. Samples loaded parallel to bedding are less compliant compared to the other loading directions. With the exception of samples deformed 45° and 90° to bedding at pc = 100 MPa, strain is localized in discrete shear zones. Compressive strength (σmax) increases with increasing pc, resulting in an internal friction coefficient of ≈ 0.31 for samples deformed at 45° and 90° to bedding, and ≈ 0.44 for samples deformed parallel to bedding. In contrast, pre-consolidation, drainage condition, T and $$\dot{\varepsilon }$$ ε ˙ do not significantly affect deformation behavior of dried samples. However, σmax and Young’s modulus (E) decrease substantially with increasing water saturation. Compared to the clay-rich shaly facies of OPA, sandy facies specimens display higher strength σmax and Young’s modulus E at similar deformation conditions. Strength and Young’s modulus of samples deformed 90° and 45° to bedding are close to the iso-stress Reuss bound, suggesting a strong influence of weak clay-rich layers on the deformation behavior.

The effect of confining pressure on elastic wave velocities and dynamic to static Young’s modulus ratio

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. D135-D142 ◽  
Author(s):  
Mohammad Reza Asef ◽  
Ali Reza Najibi
Keyword(s):  
Young’S Modulus ◽  
Atmospheric Pressure ◽  
Critical Pressure ◽  
Young's Modulus ◽  
Confining Pressure ◽  
Least Square ◽  
Oil Well ◽  
Modulus Ratio ◽  
Wave Velocities ◽  
Static Young’S Modulus

We carried out laboratory experiments under dry conditions on limestone core specimens of Sarvak formation obtained from an oil well in the southwest of Iran. Our objective was to study the effect of confining pressure on the compressional and shear wave velocities ([Formula: see text], [Formula: see text]), and on the dynamic to static Young’s modulus ratio ([Formula: see text]). Furthermore, we made attempts to predict [Formula: see text] and [Formula: see text] at atmospheric pressure based on the same velocities at various confining pressures. These analyses revealed that, below a critical pressure with an increase in confinement [Formula: see text] and [Formula: see text] increased exponentially, representing a poroelastic regime. Above a critical pressure, however, the trend was linear. Likewise, we observed that with an increase in confinement, [Formula: see text] initially decreased exponentially, followed by a linear decreasing trend above the critical pressure. This indicated that [Formula: see text] is more responsive than [Formula: see text]. Accordingly, these observations infer that it is possible to predict [Formula: see text] based on [Formula: see text] at different confining stresses. This is an important improvement for geomechanical modeling of hydrocarbon and geothermal reservoirs because static parameters are more realistic input parameters. Besides, we derived the coefficients of the velocity-pressure equation for Sarvak limestone using least square regression analysis. More interestingly, we predicted [Formula: see text] and [Formula: see text] at atmospheric pressure based on these coefficients. Good agreement was observed between measured and predicted velocities at atmospheric pressure. Analysis of similar published experiments on oceanic basalts strongly confirmed these observations.

scholarly journals The energy evolution characteristics of coal under different dynamic strain rates and confining pressures

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1409-1416
Author(s):  
Yi-Qiang Lu ◽  
Xiao-Hui Liu ◽  
Jing Xie ◽  
Zhi-Qiang He ◽  
Cong Li
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Confining Pressure ◽  
Tensile Failure ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Strengthening Effect ◽  
Peak Strain ◽  
Energy Evolution ◽  
Evolution Characteristics ◽  
Confining Pressures

Coal specimens from baijiao coal mine were impacted by a split Hopkinson pressure bar to study its dynamic mechanical behavior under different confining pressures (0-12 MPa) and different strain rates (20-250 s-1). The performances and the energy evolution characteristics of the coal specimens were analyzed. The results show that the strengthening effect and toughening effect of rock are gradually enhanced with the increase of confining pressure. At the same time, the coal failure gradually transitions and develops from tensile failure to compression-shear failure under the action of confining pressure. The peak strength and peak strain of coal rock show significant strain rate correlation and strong confining pressure effect with the change of confining pressures and strain rates. The dynamic strength growth factor of coal is approximately linear with the increasing of strain rates. The energy density and energy absorption density increase linearly with the increase of strain rates, and the energy consumption ratio has a logarithmic growth relationship with the strain rates.

scholarly journals Static and Dynamic Mechanical Properties of Organic-Rich Gas Shale

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Hui Li ◽  
Chi Dong ◽  
Hongwei Yu ◽  
Xin Zhao ◽  
Yan Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Dynamic Properties ◽  
Confining Pressure ◽  
Dynamic Mechanical Properties ◽  
Eagle Ford Shale ◽  
Eagle Ford ◽  
Dynamic Mechanical ◽  
Rock Mechanical Properties

Rock mechanical properties are critical for drilling, wellbore stability, and well stimulation. There are usually two laboratory methods to determine rock mechanical properties: static compression tests and acoustic velocity measurements. Rocks are heterogeneous, so there are significant differences between static elastic constants and the corresponding dynamic ones. Usually, static test results are more representative than dynamic methods but the static tests are time consuming and costly. Dynamic methods are nondestructive and less expensive, which are practical in the laboratory and field. In this paper, we compare the static and dynamic elastic properties of Eagle Ford Shale by triaxial compressive tests and ultrasonic velocity tests. Correlations between static and dynamic elastic properties are developed. Conversion from dynamic mechanical properties to static mechanical properties is established for better estimating reservoir mechanical properties. To better understand the relationship of static and dynamic mechanical properties, 30 Eagle Ford Shale samples were tested. According to the test results, the dynamic properties are considerably different from the static counterparts. For all tested samples, static Young’s modulus is lower than dynamic Young’s modulus, ranging from 55% to 90%. The difference of the static and dynamic Young’s moduli decreases with the increasing of confining pressure. The reason may be because the microcracks closed in high confining pressure. Correlations between static and dynamic Young’s modulus are developed by regression analysis, which are crucial to understand the rock mechanical properties and forecast reservoir performance when direct measurement of static mechanical properties is not available or expensive. There are no strong correlations between static and dynamic Poisson’s ratios observed for the tested samples. Two potentially major reasons for the discrepancy of the static and dynamic properties of Eagle Ford Shale are discussed. Lithology and heterogeneity may be the inherent reasons, and external causes are probably the difference in strain amplitude and frequency.

Study on the Strength Characteristics of Municipal Solid Waste

2011 ◽  
Vol 204-210 ◽  
pp. 1835-1838
Author(s):  
Zhen Ying Zhang ◽  
Da Zhi Wu
Keyword(s):  
Municipal Solid Waste ◽  
Solid Waste ◽  
Effective Stress ◽  
Large Scale ◽  
Void Ratio ◽  
Axial Strain ◽  
Confining Pressure ◽  
Strength Characteristics ◽  
Initial Void Ratio ◽  
Confining Pressures

Basing on the traditional tri-axial test on large-scale samples, the strength characteristics of municipal solid waste have been studied. The municipal solid waste is divided into three parts: incompressible solid waste material, reinforced material that is difficult to be biodegraded and the material that is easy to be biodegraded. The proportions of these three parts are 35%, 15% and 50%, respectively. Laboratory test has been performed for different initial void ratios, different proportion of ingredients and different confining pressures. The testing results show that the initial void ratio is the main factor that influences the strength of the municipal solid waste. Besides, the principle effective stress increases with the axial strain in a hardening increasing trend, even though the total axial strain has reached 40%. The principle effective stress also increases with the confining pressure that applied on the testing sample. Furthermore, the principle effective stress decreases with the increasing of the initial void ratio.

scholarly journals Novel method and case study of a deep shale fracability evaluation based on the brittleness index

2021 ◽  
pp. 014459872110336
Author(s):  
Cong Lu ◽  
Li Ma ◽  
Jianchun Guo ◽  
Xinyang Li ◽  
Yunchuan Zheng ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Shale Gas ◽  
Evaluation Method ◽  
Young's Modulus ◽  
Fracture Morphology ◽  
Brittleness Index ◽  
Peak Strain ◽  
Dilatancy Angle ◽  
Novel Method ◽  
Weight Coefficients

Deep shale has gradually become a focus point for unconventional natural gas exploration and development in China and even the world. The key to deep shale development is the fracability evaluation of a reservoir; conventional evaluation methods cannot provide accurate evaluations of deep shale fracability under high confining pressures. In this study, experimental methods are used to obtain the mechanical parameters, mineral composition, and stress–strain characteristics of shale. The fracture complexity coefficient based on the fractal dimension and fracture angle is defined by analyzing the fracture morphology of shale samples. Using the rock fracturing complexity as an index, the weight coefficients of different factors for the shale fracture morphology are obtained, thus establishing a new evaluation model for the deep shale brittleness index. The results show that the Young's modulus, dilatancy angle, and peak strain are the main factors affecting the complexity of shale fractures. The gray correlation theory is used to calculate the weights of various factors in the model. The weight coefficients of the Young's modulus, dilatancy angle, and peak strain on the rock brittleness index are 0.262, 0.353, and 0.385, respectively. Based on this, a novel method for evaluating the fracability of deep shale using the brittleness index is proposed. The fracability index of the horizontal section of the deep shale gas well in this area was calculated, and the location of the fracturing perforation cluster was optimized accordingly. This technology has been successfully applied in more than 10 deep shale gas wells in the southern Sichuan Basin, effectively reducing the fracturing pressure by 5–10 MPa, increasing the average daily production of a single well by 15.3 ×  104 m3. This paper proposes a novel fracability evaluation method for deep shale based on the brittleness index, which provides a reference for optimizing deep shale fracturing design.

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