Influence Analysis and Stepwise Regression of Coal Mechanical Parameters on Uniaxial Compressive Strength Based on Orthogonal Testing Method

Uniaxial compressive strength (UCS) and peak strain (PS) are essential indices for studying the mechanical properties of coal and rock masses, and they are closely related to mechanical parameters such as the elastic modulus (E), Poisson’s ratio (υ), cohesion (C) and internal friction angle (Φ) of coal and rock masses. This study took the No. 2-1 coal seam of Zhaogu No. 2 Mine, in Henan Province, China, as the research object. An RMT-150B servo testing machine was used to test all mechanical parameters, including the E, υ, C and Φ of coal and rock masses. Based on the principle of orthogonal testing, Three Dimensions Fast Lagrangian Analysis of Continua (FLAC3D) was used to select E, υ, C, Φ, tensile strength (Rm) and dilation angle (Ψ) as initial participation factors. Using these six parameters and a five-level combination scheme (L25 (56)), the influence of coal mechanical parameters on UCS and PS was investigated, using the software SPSS for stepwise regression analysis, and a uniaxial pressure-resistant regression prediction equation was established. The research showed that, under uniaxial compression conditions, the main parameters controlling UCS of coal masses are C and Φ; conversely, the main parameters controlling PS are E and C. UCS and PS exhibit significant linear relationships with these main controlling parameters. Here, a stepwise regression prediction equation was established through reliability verification analysis using the main controlling parameters. This prediction method produces very small errors and a good degree of fit, thus allowing the rapid prediction of UCS. The precision of the stepwise regression model depends on the number of test samples, which can be increased in the later stages of a design project to further improve the precision of the projection model.

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Experimental Research on Acoustic Emission of Granite under Uniaxial Compression and Splitting Tensile

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.232.24 ◽

2012 ◽

Vol 232 ◽

pp. 24-27

Author(s):

Zong Zhan Li ◽

Jun Lin Tao ◽

Yi Li

Keyword(s):

Compressive Strength ◽

Acoustic Emission ◽

Uniaxial Compression ◽

Uniaxial Compressive Strength ◽

Loading Rate ◽

Testing Machine ◽

Peak Stress ◽

Uniaxial Compression Test ◽

Peak Strain ◽

Ae Energy

This paper makes the acoustic emission of granite under uniaxial compression and splitting tensile test by electro-hydraulic testing machine and AE .We studied the relationship of uniaxial compressive strength and splitting tensile strength with the loading rate and AE characteristics of granite .The results show that uniaxial compressive strength and peak strain raise with loading rate, the AE energy gradually increases and get maximum in the 30% of the peak stress in the process of uniaxial compression test, and in the splitting tensile AE energy generates in the initial loading and gets maximum when the granite brittle fracture.

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EFFECT OF PETROLOGICAL FEATURES ON MECHANICAL PROPERTIES OF ROCK SALT FROM THE LGOM (LEGNICA–GŁOGÓW COPPER DISTRICT)

Biuletyn Państwowego Instytutu Geologicznego ◽

10.5604/01.3001.0009.4572 ◽

2016 ◽

pp. 51-64 ◽

Cited By ~ 1

Author(s):

Katarzyna CYRAN ◽

Tomasz TOBOŁA ◽

Paweł KAMIŃSKI

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Uniaxial Compressive Strength ◽

Rock Salt ◽

Fluid Inclusions ◽

Mechanical Parameters ◽

Research Results ◽

Strength Tests ◽

Crystal Boundaries

The paper presents the attempt to find a correlation between the content of impurities and mechanical parameters of rock salt from the LGOM. Research was carried out in three steps: uniaxial compressive strength tests, determination of the content of insoluble minerals (impurities), and observations under the microscope and Raman microspectroscopy. The research results reveal that the rock salt which is characterized by low content of insoluble minerals (0.13–2.11% wt.) shows no correlation between the mechanical properties and the content of impurities. However, it was found that mechanical properties depend on both the distribution of impurities in halite crystals and the presence of fluid inclusions and hydrocarbons along the crystal boundaries. Moreover, the distribution of anhydrite at the edges of halite crystals may influence an increase of rock salt strength. On the contrary, the presence of fluid inclusions and hydrocarbons along the halite crystal boundaries may reduce the rock salt strength.

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Size Effect of Uniaxial Compressive Strength of Limestone

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.229-231.233 ◽

2012 ◽

Vol 229-231 ◽

pp. 233-238 ◽

Cited By ~ 1

Author(s):

Ze Hui Chen ◽

Chang Wu Liu ◽

Ji Wei Deng

Keyword(s):

Compressive Strength ◽

Elastic Modulus ◽

Size Effect ◽

Shear Failure ◽

Testing Machine ◽

Peak Strain ◽

Test Results ◽

Effect Model ◽

Splitting Failure ◽

Uniaxial Compressive Test

Using the MTS testing machine, the uniaxial compressive test of varisized da-qing limestones were undertaken, and the effect of dimensions about compressive strength, peak strain, elastic modulus and destructional forms of rock specimens were studied. It demonstrates that along with the increase of length-diameter ratio, peak strain and compressive strength turn smaller, elastic modulus gradually increases, the destruction of rock samples have a transformation from splitting failure to shear failure. Combined with the test results, Obert L model and Yang Shengqi model, the two size-effect models with extensive applications are analyzed and contrasted. And the conclusion is drawn that Obert L model has a relatively broad applicability, while Yang Shengqi model has a stronger Targeting and higher accuracy. Thus based on the Yang Shengqi model, the size-effect model of da-qing limestone is put forward, and the result indicates that this model corresponds well with the test results, having certain practical value.

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Relation between Uniaxial Compressive Strength and Physical Parameters of Rock in a Nuclear Power Plant

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.865.373 ◽

2017 ◽

Vol 865 ◽

pp. 373-382

Author(s):

Jing Sen Liu ◽

Hai Bo Li ◽

Bo Liu ◽

Guo Kai Zhang ◽

Wei Zhou

Keyword(s):

Compressive Strength ◽

Power Plant ◽

Nuclear Power Plant ◽

Uniaxial Compressive Strength ◽

Nuclear Power ◽

Empirical Equation ◽

P Wave ◽

Physical Parameters ◽

Mechanical Parameters ◽

P Wave Velocity

In order to improve the accuracy of the selection on rock mechanical parameters, the relation between uniaxial compressive strength (UCS) and physical mechanical parameters should be investigated. A great number of physical and mechanical tests on rock in the first-stage of Guangxi Fangchenggang Nuclear Power Plant (GFNPP) are conducted. Mineral identification tests of rocks are conducted, and rocks are divided into two groups (A and B) according to the result of the test. The correlation coefficient between rock UCS and rock physical parameters (porosity, density and P-wave velocity) are calculated by using Pearson’s analytical method. The result shows that the relationship between physical parameters and mechanical parameters of rock is influenced significantly by content of quartz. Regression analysis method is used to explore the relation between UCS and porosity, density, P-wave velocity of rock; combined with the dimensional analysis, the relation between UCS and rock physical parameters was established. Based on normality test and randomness test, the best fitting equation is determined as the empirical equation of UCS. The empirical equation was used to forecast the UCS of rock in the second-stage of GFNPP, comparative results show that the forecasting value and the experimental value are in good agreement.

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Effects of Kaolin Addition on Mechanical Properties for Cemented Coal Gangue-Fly Ash Backfill under Uniaxial Loading

Energies ◽

10.3390/en14123693 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3693

Author(s):

Faxin Li ◽

Dawei Yin ◽

Chun Zhu ◽

Feng Wang ◽

Ning Jiang ◽

...

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Elastic Modulus ◽

Fly Ash ◽

Uniaxial Compressive Strength ◽

Shear Failure ◽

Coal Gangue ◽

Tensile Failure ◽

Peak Strain ◽

Local Shear

In this investigation, six groups of cemented coal gangue-fly ash backfill (CGFB) samples with varying amounts of kaolin (0, 10, 20, 30, 40, and 50%) instead of cement are prepared, and their mechanical properties are analyzed using uniaxial compression, acoustic emission, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The uniaxial compressive strength, peak strain, and elastic modulus of CGFB samples decreased with the kaolin content. The average uniaxial compressive strength, elastic modulus, and peak strain of CGFB samples with 10% amount of kaolin are close to that of CGFB samples with no kaolin. The contribution of kaolin hydration to the strength of CGFB sample is lower than that of cement hydration, and the hydration products such as ettringite and calcium-silicate-hydrate gel decrease, thereby reducing strength, which mainly plays a role in filling pores. The contents of kaolin affect the failure characteristics of CGFB samples, which show tensile failure accompanied by local shear failure, and the failure degree increases with the kaolin content. The porosity of the fracture surface shows a decreasing trend as a whole. When the amount of kaolin instead of cement is 10%, the mechanical properties of CGFB samples are slightly different from those of CGFB samples without kaolin, and CGFB can meet the demand of filling strength. The research results provide a theoretical basis for the application of kaolin admixture in fill mining.

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Study on the Strength Evolution Characteristics of Cemented Tailings Backfill from the Perspective of Porosity

Minerals ◽

10.3390/min11010082 ◽

2021 ◽

Vol 11 (1) ◽

pp. 82

Author(s):

Hongwei Deng ◽

Yao Liu ◽

Weiyou Zhang ◽

Songtao Yu ◽

Guanglin Tian

Keyword(s):

Growth Rate ◽

Compressive Strength ◽

Uniaxial Compressive Strength ◽

Testing Machine ◽

Relative Strength ◽

Evolution Model ◽

Porosity Variation ◽

Strength Evolution ◽

Evolution Laws ◽

Curing Age

At present, the filling mining method is widely used. To study strength evolution laws of cemented tailings backfill (CTB) under different curing ages, in the experiment, mine tailings were used as aggregates, ordinary Portland cement (PC32.5) was used as cementing materials, and different additives (lime and fly ash) were added to make filling samples with the solids mass concentration at 74% and the cement-sand ratios 1:4, 1:6 and 1:8. Based on the nuclear magnetic resonance (NMR) technology, the porosity test of filling samples with curing ages of 3 d, 7 d and 28 d was carried out, and the uniaxial compressive strength test was carried out on the servo universal material testing machine. The relationship between the uniaxial compressive strength and porosity of backfills and the curing age in the three groups was studied, and change laws of the porosity variation and strength growth rate of backfills were analyzed. Based on the variation in porosity, the strength evolution model of the CTB under different curing ages was established, and the model was fitted and verified with test data. Results show that the uniaxial compressive strength, porosity, porosity variation, and strength growth rate of the three groups of backfills gradually increase with the increase of the curing age, the porosity of backfill basically increases with the decrease of the cement–sand ratio, and the porosity of backfill decreases with the increase of the curing age. Porosity variations and relative strength values of the three groups of backfills under different cement-sand ratios obey an exponential function, and the two have a good correlation, indicating that the established filling strength evolution model can well reflect strength evolution laws of the CTB with the change of curing age.

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Differences of Mechanical Parameters and Rockburst Tendency Indices between Coal and Non-Coal Rocks and Modified Rockburst Tendency Classification Criteria for Non-Coal Rocks

Applied Sciences ◽

10.3390/app11062641 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2641

Author(s):

Kun Du ◽

Yu Sun ◽

Songge Yang ◽

Shizhan Lv ◽

Shaofeng Wang

Keyword(s):

Compressive Strength ◽

Uniaxial Compressive Strength ◽

Dynamic Fracture ◽

Poisson’S Ratio ◽

Elastic Strain Energy ◽

Classification Criteria ◽

Poisson's Ratio ◽

Uniaxial Tensile ◽

Mechanical Parameters ◽

Energy Index

Rockbursts represent hazardous dynamic disasters for underground coal mines and other underground rock engineering projects. Some bursting liability indices are put forward and applied to identify the likelihood of rock burst occurrence. The classification criteria of the bursting liability indices are proved to be reasonable for coals, but they are still immature for non-coal rocks. Thus, it is uncertain that it is reasonable to use the classification criteria of coal for evaluating the bursting liability of non-coal rocks. Hence, in this study, a large amount of data, such as the basic mechanical parameters, i.e., Poisson’s ratio μ, elastic modulus E, uniaxial compressive strength σc, and uniaxial tensile strength σt, and the bursting liability indices, i.e., elastic strain energy index WET, bursting energy index Wcf, dynamic fracture duration time DT, and brittleness index B, of different coals and non-coal rocks were collected in China. Then, the differences of mechanical parameters and rockburst tendency indices between coal and non-coal rocks were studied systematically, and apart from the Poisson’s ratio μ, the other three basic mechanical parameters of coal and non-coal rocks have great differences in data distribution and concentration scope, which proved that the non-coal rocks cannot share the same index system and classification criteria of coals. In addition, the evaluation results of a single index for rock bursting liability of rocks were directly compared in pairs, and the inconsistency rate for coals is about 42–68%. It is necessary to build a comprehensive evaluation method to evaluate the bursting liability of rocks. At last, the modified rockburst tendency classification criteria for non-coal rocks were put forward. It is reasonable to use the classification criteria of the WET and Wcf to classify the bursting liability of non-coal rocks, while it is unreasonable to use that of the DT and σc. It has been concluded that the index B are more suitable for non-coal rocks, and a new index, named strength decrease rate (SDR), was proposed to determine the bursting liability, which is the ratio of uniaxial compressive strength σc to duration of dynamic fracture DT.

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Experimental and Modeling Study on the Strength of Tailings Backfill in Underground Mine

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.522-524.1390 ◽

2014 ◽

Vol 522-524 ◽

pp. 1390-1393 ◽

Cited By ~ 1

Author(s):

Gang Huang ◽

Si Jing Cai ◽

Ya Dong Zhang ◽

Di Wu

Keyword(s):

Compressive Strength ◽

Uniaxial Compressive Strength ◽

Testing Machine ◽

Underground Mine ◽

Strength Testing ◽

Curing Time ◽

Mass Ratio ◽

Theory Analysis ◽

Object Of Study ◽

The Mathematical Model

Taking backfill material of underground mine as the object of study, this paper conducts the research on its strength characteristics by using uniaxial compressive strength testing machine at different cement-sand mass ratio and curing time and mass concentration which the method of experiment and theory analysis were used. The model of predicting the strength of tailings backfill was introduced, and its results were identical with the expreimental test after comparing. Therefore, the mathematical model can be used to estimate the strength of tailings backfill after assigning the specific value of tailing backfill. The tested results show that the uniaxial compressive strength of backfill rose with the increase of its concentration, cement-sand ratio, and the curing time; the strength of backfill was not enough to sustain the stope if the curing time is short and the cement-sand ratio is small.

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Weathering Influence on Properties of Siltstones from Istria, Croatia

Advances in Materials Science and Engineering ◽

10.1155/2016/3073202 ◽

2016 ◽

Vol 2016 ◽

pp. 1-15 ◽

Cited By ~ 9

Author(s):

Martina Vivoda Prodan ◽

Željko Arbanas

Keyword(s):

Compressive Strength ◽

Size Distribution ◽

Uniaxial Compressive Strength ◽

Fragment Size ◽

Slope Instability ◽

Engineering Properties ◽

Rock Masses ◽

Weak Rocks ◽

Erosion Processes ◽

Weathering Grades

Slaking and weathering of weak rocks result in slope instability. Siltstones from flysch rock masses are highly susceptible to weathering, which causes rapid changes in the geotechnical properties and durability. This study investigated siltstone samples of different weathering grades from flysch rock masses from the Istria Peninsula, Croatia, and determined the effects of weathering on their engineering properties. Laboratory testing of siltstone samples of different weathering grades was conducted to determine the specific gravity, grain size distribution, Atterberg limits, and uniaxial compressive strength. The standardized slake durability index is not sufficient to classify the durability of weak rock masses such as siltstones. Therefore, the durability of siltstone samples of different weathering grades was quantified from the fragment size distribution after each of five slaking cycles. The tested samples were classified based on the disintegration ratio, and the modified disintegration ratio was used to determine potential long-term degradation of the tested samples. The results indicated that weathering has a significant influence on the plasticity, uniaxial compressive strength, and durability characteristics and thus affects the landslides and erosion processes in siltstones in the flysch zone of the Istria Peninsula.

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Influence of Water Content on the Mechanical Parameters of the Intact Rock and Rock Mass

Periodica Polytechnica Civil Engineering ◽

10.3311/ppci.12173 ◽

2018 ◽

Author(s):

Balázs Vásárhelyi ◽

Morteza Davarpanah

Keyword(s):

Tensile Strength ◽

Compressive Strength ◽

Rock Mass ◽

Internal Friction ◽

Water Content ◽

Uniaxial Compressive Strength ◽

Water Saturation ◽

Friction Angle ◽

Intact Rock ◽

Mechanical Parameters

The goal of this paper is to present the influence of the water saturation of the intact rock on different mechanical parameters, such as internal friction angle, cohesion, Hoek-Brown constant (mi ). Analyzing the previously published results, it was found that due to water saturation both the uniaxial compressive strength and tensile strength decrease similarly, i.e. the ratio of these two values is constant, thus the internal friction angle does not change but only the cohesion. Likewise, Hoek-Brown constant (mi ) remains constant; it is independent on the moisture content.The ratio of the elastic modulus and the uniaxial compressive strength of the intact rock is also calculated. According to the laboratory results, this ratio (namely modulus ratio) is also independent on the water content.It is shown that the mechanical parameters of the rock mass (such as compressive strength, tensile strength, deformation modulus) similarly depend on the water content than the intact rock.

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