scholarly journals Predicting the Mechanical Properties of Bimrocks with High Rock Block Proportions Based on Resonance Testing Technology and Damage Theory

2019 ◽  
Vol 9 (17) ◽  
pp. 3537
Author(s):  
Yuexiang Lin ◽  
Limin Peng ◽  
Mingfeng Lei ◽  
Xiang Wang ◽  
Chengyong Cao
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Rock Block ◽  
Dynamic Elastic Modulus ◽  
Parameter Determination ◽  
Design Parameters ◽  
Damage Theory ◽  
Design And Construction

Block-in-matrix-rocks (bimrocks) are very complicated geological masses that cause many challenging problems during the design and construction of engineering projects, such as parameter determination and landsliding. Successful engineering design and construction depends on a suitable constitutive model and reliable design parameters for geological masses. In this paper, the vibration attenuation signal of welded bimrocks was obtained and studied using resonance test technology. Combined with a uniaxial compression test, a constitutive model was proposed to describe the mechanical behavior of welded bimrocks. On this basis, the relations between the dynamic elastic modulus and the physical parameters of bimrocks were established, which included macroscopic mechanical parameters and damage constitutive parameters. Consequently, a new technological process was proposed to provide quick identification of the mechanical properties of welded bimrocks. The results indicate that the dynamic elastic modulus is highly correlated with the rock block proportion (RBP) and uniaxial compression strength (UCS). It is an effective parameter to predict the strength of the bimrocks with high RBPs. Additionally, the proposed constitutive model, which is based on damage theory, can accurately simulate the strain softening behavior of the bimrocks. Combining the resonant frequency technology and the proposed constitutive model, the complete stress strain curve can be obtained in a rapid and accurate manner, which provides a further guarantee of the stability and safety of underground engineering.

scholarly journals Evaluation Method of Granite Multiscale Mechanical Properties Based on Nanoindentation Technology

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Man Lei ◽  
Fa-ning Dang ◽  
Haibin Xue ◽  
Mingming He
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Evaluation Method ◽  
Poisson Ratio ◽  
Nanoindentation Test ◽  
Uniaxial Compression Test ◽  
Displacement Curve ◽  
Mineral Contents

In order to study the mechanical properties of granite at the micro- and nanoscale, the load-displacement curve, residual indentation information, and component information of the quartz, feldspar, and mica in granite were obtained using a nanoindentation test, a scanning electron microscope (SEM), and X-ray diffraction (XRD). The elastic modulus and the hardness of each component of the granite were obtained through statistical analysis. Treating rock as a composite material, the relation between the macro- and microscopic mechanical properties of rock was established through the theory of micromechanical homogenization. The transition from micromechanical parameters to macromechanical parameters was realized. The equivalent elastic modulus and Poisson’s ratio of the granite were obtained by the Self-consistent method, the Dilute method, and the Mori-Tanaka method. Compared with the elastic modulus and the Poisson ratio of granites measured by a uniaxial compression test and the available data, the applicability of the three methods were analyzed. The results show that the elastic modulus and hardness of the quartz in the granite is the largest, the feldspar is the second, the mica is the smallest. The main mineral contents in granite were analyzed using the semiquantitative method by XRD and the rock slice identification test. The elastic modulus and the Poisson ratio of granite calculated by three linear homogenization methods are consistent with those of the uniaxial compression test. After comparing the calculation results of the three methods, it is found that the Mori-Tanaka method is more suitable for studying the mechanical properties of rock materials. This method has an important theoretical significance and practical value for studying the quantitative relationship between macro- and micromechanical indexes of brittle materials. The research results provide a new method and an important reference for studying the macro-, micro-, and nanomechanical properties of rock.

Experimental Investigation into the Influences of Weathering on the Mechanical Properties of Sedimentary Rocks

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiaoshuang Li ◽  
Yingchun Li ◽  
Saisai Wu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Friction Coefficient ◽  
Uniaxial Compression ◽  
Sedimentary Rocks ◽  
Uniaxial Tensile ◽  
Mechanical Parameters ◽  
Uniaxial Tensile Strength ◽  
Weathering Grades

The time-dependent behaviors of the sedimentary rocks which refer to the altering of the mechanical and deformable properties of rock elements in the long-term period are of increasing importance in the investigation of the failure mechanism of the rock strata in underground coal mines. In order to obtain the accurate and reliable mechanical parameters of the sedimentary rocks at different weathering grades, the extensive experimental programs including the Brazilian splitting test, uniaxial compression tests, and direct shear tests have been carried out on the specimens that exposed to the nature environments at different durations. The correlation between the weathering grades and mechanical parameters including uniaxial tensile strength, uniaxial compression strength, elastic modulus, Poisson’s ratio, cohesion, and friction coefficient was proposed. The obtained results suggested that uniaxial tensile strength, uniaxial compressive strength, elastic modulus, and cohesion dramatically decreased with increasing weathering time, characterized as the negative exponential relationship in general. The influences of various weathering grades on fracture behavior of the rock specimens were discussed. The cumulative damage of the rock by the weathering time decreased the friction coefficient of the specimens which led to the initiation and propagation of microcrack within the rock at lower stress conditions. The obtained results improved the understanding of the roles of weathering on the mechanical properties of sedimentary rocks, which is helpful in the design of the underground geotechnical structures.

scholarly journals Physical and Mechanical Properties Evolution of Coal Subjected to Salty Solution and a Damage Constitutive Model under Uniaxial Compression

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3264
Author(s):  
Min Wang ◽  
Qifeng Guo ◽  
Yakun Tian ◽  
Bing Dai
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Immersion Time ◽  
Physical And Mechanical Properties ◽  
Relative Mass ◽  
Stress Strain ◽  
Damage Constitutive Model ◽  
Underground Reservoirs

Many underground reservoirs for storing water have been constructed in China’s western coal mines to protect water resources. Coal pillars which work as dams are subjected to a long-term soaking environment of concentrated salty water. Deterioration of the coal dam under the attack of the salty solution poses challenges for the long-term stability and serviceability of underground reservoirs. The evolution of the physical and mechanical properties of coal subjected to salty solutions are investigated in this paper. Coal from a western China mine is made to standard cylinder samples. The salty solution is prepared according to chemical tests of water in the mine. The coal samples soaked in the salty solution for different periods are tested by scanning electron microscope, nuclear magnetic resonance, and ultrasonic detector techniques. Further, uniaxial compression tests are carried out on the coal specimens. The evolutions of porosity, mass, microstructures of coal, solution pH values, and stress–strain curves are obtained for different soaking times. Moreover, a damage constitutive model for the coal samples is developed by introducing a chemical-stress coupling damage variable. The result shows that the corrosion effect of salty solution on coal samples becomes stronger with increasing immersion time. The degree of deterioration of the longitudinal wave velocity (vp) is positively correlated with the immersion time. With the increase in soaking times, the porosity of coal gradually increases. The relative mass firstly displays an increasing trend and then decreases with time. The peak strength and elastic modulus of coal decreases exponentially with soaking times. The developed damage constitutive model can well describe the stress–strain behavior of coal subjected to salty solution under the uniaxial compression.

The Effect of Andreasen ́s Packing Distribution Modulus on the Physical and Mechanical Properties of a Low Cement Refractory Castable

2019 ◽  
Vol 1156 ◽  
pp. 97-104
Author(s):  
Vitoria Gabrieli Malimpensa ◽  
José Antonio Alves Júnior ◽  
João Baptista Baldo
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Refractory Concrete ◽  
Physical And Mechanical Properties ◽  
Dynamic Elastic Modulus ◽  
Conventional Concrete ◽  
Key Indicator ◽  
Temperature Ranges ◽  
S Model ◽  
First Time

Among modern refractory concretes (MRC), those with low cement content (LCC) where CAC = 4-6wt%, are widely commercialized, considering that their properties approximate those of burned bricks of the same class. In this work, the effect of the modulus q of Andreasen ́s particle size distribution, on the physical (porosity, bulk density) and mechanical (flexural strength and dynamic elastic modulus) properties, of either pre-fired or simply dried specimens of a ≥85% Al2O3 LCC ́s, was investigated. The different LCC ́s samples were formulated according to the Andreasen ́s model, using several distribution modulus (q = 0.22, 0.26, 0.30, 0.33 and 0.42). Measurements of the Dynamic Elastic Modulus (DEM) as a function of temperature (25 to 1500°C), using the Impulse Excitation Technique (IET), were taken as a key indicator of the microstructure dynamic behavior. For the sake of just a punctual comparative term, the physical and mechanical properties of a conventional type refractory concrete (CRC) with a higher CAC percentage (15%) formulated with q = 0.26 was also evaluated. The results indicated that distribution modulus values of; q =0.22, 0,26, 0.30 and 0.33 lead to higher DEM values. While q=0.42 lead to the smallest value in the LCC series. Also, higher DEM values ​​were obtained for LCC ́s (CAC = 5%) than for conventional concrete with CAC = 15% under the same value of q for pre-fired samples. In addition, by observing the occurrence of damping effects in specific temperature ranges, the loss of crystallization water from the calcium aluminate hydrates, as well as the development of pyroplastic behavior could be inferred. The gathered information is relevant to predict the behavior of LCC ́s and CRC ́s when put into service for the first time.

Uniaxial Compression Fractal Damage Constitutive Model of Rock Subjected to Freezing and Thawing

2020 ◽  
Author(s):  
Shengtao Zhou ◽  
Nan Jiang ◽  
Xuedong Luo ◽  
Wen Fang ◽  
Xu He
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Residual Strength ◽  
Structural Damage ◽  
Compression Fracture ◽  
Peak Strain ◽  
Freeze Thaw ◽  
Deformation Stage ◽  
Damage Constitutive Model

Mechanical properties of the rock in the cold regions are often affected by freeze-thaw cycles and loads. It is of great theoretical significance and engineering value to establish a uniaxial compression damage constitutive model of the rock under freeze-thaw cycles that can reflect the relationship between macroscopic and mesoscopic structural damage. In this paper, macroscopic and mesoscopic methods are combined with statistical methods to quantitatively analyze the damage degree of rock under freeze-thaw cycles and loads. Combined with the fractal features of the macroscopic image of the section, a fractal damage constitutive model considering the residual strength of rock is established. In addition, the model is subsequently verified by the experiment. The experiment shows that the mechanical properties of rocks subjected to freeze-thaw cycles and loads are determined by freeze-thaw damage variables, load damage variables, and their coupling effects. As the number of freeze-thaw cycles increases, the uniaxial compressive strength and elastic modulus of rocks decrease, and peak strain increases. By using the fractal dimension of the compression fracture surface as a bridge considering the residual strength of the rock, the constitutive model can better reflect the compaction stage, elastic deformation stage and plastic deformation stage of the uniaxial compression process of the freeze-thaw rocks.

scholarly journals SHPB Testing and Analysis of Bedded Shale under Active Confining Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Guoliang Yang ◽  
Jingjiu Bi ◽  
Xuguang Li ◽  
Jie Liu ◽  
Yanjie Feng
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Mechanical Properties ◽  
Dynamic Elastic Modulus ◽  
Peak Strain ◽  
Dynamic Mechanical ◽  
Bedding Angle

Shale gas is the most important new energy source in the field of energy, and its exploitation is very important. The research on the dynamic mechanical properties of shale is the premise of exploitation. To study the dynamic mechanical properties of shale from the Changning-Weiyuan area of Sichuan Province, China, under confining pressure, we used a split Hopkinson pressure bar (SHPB) test system with an active containment device to carry out dynamic compression tests on shale with different bedding angles. (1) With active confining pressure, the shale experiences a high strain rate, and its stress-strain curve exhibits obvious plastic deformation. (2) For the same impact pressure, the peak stress of shale describes a U-shaped curve with an increasing bedding angle; besides, the peak stress of shale with different bedding angles increases linearly with rising confining pressure. The strain rate shows a significant confining pressure enhancement effect. With active confining pressure, the peak strain gradually decreases as the bedding angle increases. (3) As a result of the influence of different bedding angles, the dynamic elastic modulus of shale has obvious anisotropic characteristics. Shale with different bedding angles exhibits different rates of increase in the dynamic elastic modulus with rising confining pressure, which may be related to differences in the development of planes of weakness in the shale. The results of this study improve our understanding of the behavior of bedded shale under stress.

Uniaxial compression mechanical properties and damage constitutive model of limestone under osmotic pressure

2021 ◽  
pp. 105678952110454
Author(s):  
Zhanping Song ◽  
Tong Wang ◽  
Junbao Wang ◽  
Kehui Xiao ◽  
TengTian Yang
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Osmotic Pressure ◽  
Uniaxial Compression ◽  
Influencing Factor ◽  
Peak Strain ◽  
Strain Response ◽  
Test Results ◽  
Stress Strain ◽  
Compaction Factor

To study the influence of osmotic pressure on the uniaxial compression mechanical properties of limestone, uniaxial compression tests were carried out on limestone specimens under different osmotic water pressure. The test results show that with the increase of osmotic pressure, the closure strain, yield strain and peak strain of limestone gradually increase, while the closure stress, yield stress, peak stress and elastic modulus gradually decrease. To describe the stress-strain response of limestone during uniaxial compression failure, the concepts of compaction factor and osmotic pressure influencing factor were proposed, and a constitutive model of rock compaction stage was established by integrating the relationship between the compaction factor and osmotic pressure influencing factor and the tangent modulus of compaction section. On this basis, combining the continuum damage mechanics theory, and assuming that the rock micro-unit strength obeys the compound power function distribution, a constitutive model reflecting the uniaxial compression mechanical properties of rock under osmotic pressure was established by the statistical method. The rationality of the model was verified using the results of the uniaxial compression test of limestone under different osmotic pressures. The results show that the test results under different osmotic pressures are in good agreement with the theoretical curves, and the model in this paper can reflect the stress-strain response of limestone before its failure under different osmotic pressures.

scholarly journals Effect of High Temperature and Inclination Angle on Mechanical Properties and Fracture Behavior of Granite at Low Strain Rate

2020 ◽  
Vol 12 (3) ◽  
pp. 1255 ◽  
Author(s):  
Liang Chen ◽  
Xianbiao Mao ◽  
Peng Wu
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Elastic Modulus ◽  
Crack Initiation ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Shear Failure ◽  
Nuclear Waste Repository ◽  
Compression Stress ◽  
Peak Compression

Comprehensive understanding of the effects of temperature and inclination angle on mechanical properties and fracture modes of rock is essential for the design of rock engineering under complex loads, such as the construction of nuclear waste repository, geothermal energy development and stability assessment of deep pillar. In this paper, a novel inclined uniaxial compression (inclined UCS) test system was introduced to carry out two series of inclined uniaxial compression tests on granite specimens under various inclination angles (0–20°) and treated temperatures (25–800 °C) at 5° inclination. Experimental results revealed that the peak compression stress and elastic modulus gradually decreased, while peak shear stress increased nonlinearly with the increasing inclination angle; the peak compression and shear stress as well as elastic modulus slightly increased from 25 to 200 °C, then gradually decreased onwards with the increasing temperature. The effect of temperature on peak axial strain was the same as that on peak shear displacement. Acoustic emission (AE) results suggested that the relationship between crack initiation stress, inclination angle and treated temperature followed a similar trend as that of the peak compression stress and elastic modulus. Particularly, the crack initiation (CI) stress threshold and shear stress corresponding to CI threshold under 800 °C were only 7.4% of that under 200 °C and revealed a severe heat damage phenomenon, which was consistent with the results of the scanning electron microscopy (SEM) with the appearance of a large number of thermal pores observed only under 800 °C. The failure modes tended to shear failure with the increasing inclination angle, indicating that the shear stress component can accelerate sliding instability of rocks. On the other hand, the failure patterns with different temperatures changed from combined splitting-shear failure (25–400 °C) to single shear failure (600 and 800 °C). The study results can provide an extremely important reference for underground thermal engineering construction under complex loading environment.

Study on Mechanical Properties of Iron Wire Cement Mortar

2012 ◽  
Vol 594-597 ◽  
pp. 816-819
Author(s):  
Zhi Hao Liu ◽  
Chuan Xiao Liu ◽  
Dong Chen Huang ◽  
Long Wang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Cement Mortar ◽  
Experimental Results ◽  
Uniaxial Compression Test ◽  
Mass Ratio ◽  
Iron Wire

Through the uniaxial compression test, the mechanical properties of different placements of iron wire cement mortar, e.g. compressive strength and elastic modulus, were studied, and the mass ratios of cement, sands and water influencing the mechanical properties were put forward, which provided the experimental results for reference for the wide use of the iron wire cement mortar material. From the study it is gained that: (1) The best placement of the iron wires in cement mortar is horizontal. (2) The best mass ratio of the cement, sands and water is 1:4.70:0.81.

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