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

Minerals ◽  
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.

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

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.

scholarly journals Effect of Mould Size on Compressive Strength of Green Concrete Cubes

2019 ◽  
Vol 5 (5) ◽  
pp. 1181-1188
Author(s):  
Bashir Ahmed Memon ◽  
Mahboob Oad ◽  
Abdul Hafeez Buller ◽  
Sajjad Ahmed Shar ◽  
Abdul Salam Buller ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Input Parameter ◽  
Testing Machine ◽  
Recycled Aggregates ◽  
Load Testing ◽  
Standard Size ◽  
Concrete Aggregates ◽  
Coarse Aggregates ◽  
Increasing Load ◽  
Curing Age

This paper is aimed to evaluate the effect of mould size on compressive strength of concrete cubes made with recyclable concrete aggregates. Natural coarse aggregates were replaced with 50% recycled aggregates from old demolished concrete. Five different mould sizes were used to cast 420 concrete cubes using 1:2:4 mix and 0.55 water/cement ratio. In each size equal number of cubes was cured for 3, 7, 14 and 28-day. After curing, weight of cubes was determined followed by testing for compressive strength in universal load testing machine with gradually increasing load. From the obtained results the strength correction coefficients were computed keeping 28-day cured standard size cubes as control specimens. Also, numerical expression based on regression analysis was developed to predict the compressive strength using weight of cube, area of mould and curing age as input parameter. The numerical equation predicts the compressive strength very well with maximum of 10.86% error with respect to experimental results. 

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

2014 ◽  
Vol 522-524 ◽  
pp. 1390-1393 ◽  
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.

Experimental Study on Compressive Strength of Recycled Concrete

2011 ◽  
Vol 261-263 ◽  
pp. 75-78 ◽  
Author(s):  
Yi Li ◽  
Jun Lin Tao ◽  
Ting Lei ◽  
Jian Jun Xie
Keyword(s):  
Growth Rate ◽  
Compressive Strength ◽  
Coarse Aggregate ◽  
Testing Machine ◽  
Recycled Concrete ◽  
Concrete Compressive Strength ◽  
Replacement Ratio ◽  
Recycled Coarse Aggregate ◽  
Study Results ◽  
Compressive Strength Test

Recycled concrete which are made by waste concrete has significance of environmental protection and saving natural resources. But there are different study results of recycled concrete of domestic and foreign scholars, so it is necessary to do the further study of recycled concrete. Compressive strength test of 225 concrete standard cube specimens have been done by Hydraulic Type Universal Testing Machine, and the relationships among recycled concrete compressive strength, age and recycled coarse aggregate replacement ratio have been studied. The results show: the growth rate of early strength of recycled concrete is smaller than natural concrete of the same gradation and the growth rate of later strength of recycled concrete is faster than natural concrete; when the recycled coarse aggregate replacement ratio increases the compressive strength of concrete decreases, and when the recycled coarse aggregate replacement ratio is over 70%, the decrease ranges more apparent.

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

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3640
Author(s):  
Peipeng Zhang ◽  
Jianpeng Wang ◽  
Lishuai Jiang ◽  
Tao Zhou ◽  
Xianyang Yan ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Stepwise Regression ◽  
Testing Machine ◽  
Prediction Equation ◽  
Uniaxial Pressure ◽  
Peak Strain ◽  
Mechanical Parameters ◽  
Rock Masses ◽  
Combination Scheme

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.

scholarly journals Evaluation of measurement uncertainty for the determination of the mechanical resistance of the brick samples by using uniaxial compressive strength test

2018 ◽  
Vol 9 ◽  
pp. 12 ◽  
Author(s):  
Klodian Dhoska ◽  
Saimir Tola ◽  
Agus Pramono ◽  
Indrit Vozga
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Testing Machine ◽  
Accurate Method ◽  
Standard Uncertainty ◽  
Strength Test ◽  
Mechanical Resistance ◽  
Clay Bricks ◽  
Inspection Service

Clay bricks are the most important engineering materials that can influence the quality of the construction. The quality control of the clay bricks is of prime importance to improve the quality of engineering construction. The qualities of bricks for construction applications should be checked for various types of inspection services. In this article, our inspection service was focused on compression strength test on bricks to determine their mechanical resistance and suitability for construction work. The accurate method for clay brick's production measurements has been elaborated using uniaxial compressive strength testing machine. The method was tested for a rectangular clay brick manufactured with size approximately 250 mm × 250 mm × 200 mm. The measurement method and standard uncertainty estimation of uniaxial compressive strength are briefly described in this article.

scholarly journals Experimental Investigation on Strength and Failure Characteristics of Cemented Paste Backfill

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhihong Zhang ◽  
Jiacheng Li
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Uniaxial Compressive Strength ◽  
Cement Content ◽  
Confining Pressure ◽  
Curing Temperature ◽  
Cemented Paste Backfill ◽  
Upward Trend ◽  
Paste Backfill ◽  
Curing Age

The strength characteristics of cemented paste backfill (CPB) in mining areas are key control factors for the safety assessment of overlying strata. A series of experiments about uniaxial compression and triaxial compression were carried out to study the influence of cement content of filling slurry, curing age, and curing temperature on strength behavior of CPB specimens. The failure mechanism and damage feature of CPB have been investigated. The results show the following: (1) The uniaxial compressive strength of CPB specimens exhibits an upward trend with the increase of cement content and curing age. When the cement content is high, the uniaxial compressive strength increases sharply with increasing curing age. (2) The cohesion of CPB specimens increases with the increase of cement content of filling slurry, curing age, and curing temperature. The cohesion of CPB specimens with curing age 7 days and 14 days increases linearly with increasing cement content. At the later stage of curing age, the strength growth of high cement content backfill is significantly greater than that of low cement content. The internal friction angle of the filling increases slightly with increasing filling cement content, curing age, and curing temperature. (3) The shear strength of CPB specimens at curing age 7 days exhibits an upward trend with the increase of confining pressure, while the shear strength at 14 days and 28 days curing age decreases slightly as the confining pressure increases. (4) With the increase of cement content in backfill, the brittleness increases significantly when the backfill is damaged. The failure mode of CPB specimens changes from monoclinic section shear failure to X-type failure with increasing curing age, and the failure process is divided into four stages: pore compaction, linear elastic deformation, plastic deformation, and post-peak failure.

scholarly journals Experimental Analysis of the Mechanical Properties and Resistivity of Tectonic Coal Samples with Different Particle Sizes

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2303
Author(s):  
Congyu Zhong ◽  
Liwen Cao ◽  
Jishi Geng ◽  
Zhihao Jiang ◽  
Shuai Zhang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Coalbed Methane ◽  
Coal Sample ◽  
Fine Particles ◽  
Particle Sizes ◽  
Tectonic Coal

Because of its weak cementation and abundant pores and cracks, it is difficult to obtain suitable samples of tectonic coal to test its mechanical properties. Therefore, the research and development of coalbed methane drilling and mining technology are restricted. In this study, tectonic coal samples are remodeled with different particle sizes to test the mechanical parameters and loading resistivity. The research results show that the particle size and gradation of tectonic coal significantly impact its uniaxial compressive strength and elastic modulus and affect changes in resistivity. As the converted particle size increases, the uniaxial compressive strength and elastic modulus decrease first and then tend to remain unchanged. The strength of the single-particle gradation coal sample decreases from 0.867 to 0.433 MPa and the elastic modulus decreases from 59.28 to 41.63 MPa with increasing particle size. The change in resistivity of the coal sample increases with increasing particle size, and the degree of resistivity variation decreases during the coal sample failure stage. In composite-particle gradation, the proportion of fine particles in the tectonic coal sample increases from 33% to 80%. Its strength and elastic modulus increase from 0.996 to 1.31 MPa and 83.96 to 125.4 MPa, respectively, and the resistivity change degree decreases. The proportion of medium particles or coarse particles increases, and the sample strength, elastic modulus, and resistivity changes all decrease.

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