scholarly journals Investigation of Hydraulic-Mechanical Properties of Paste Backfill Containing Coal Gangue-Fly Ash and Its Application in an Underground Coal Mine

Energies ◽  
2017 ◽  
Vol 10 (9) ◽  
pp. 1309 ◽  
Author(s):  
Xinguo Zhang ◽  
Jia Lin ◽  
Jinxiao Liu ◽  
Fei Li ◽  
Zhenzhong Pang
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Coal Mine ◽  
Coal Gangue ◽  
Underground Coal Mine ◽  
Paste Backfill

scholarly journals Experimental Investigation on Mechanical Properties of In Situ Cemented Paste Backfill Containing Coal Gangue and Fly Ash

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xinguo Zhang ◽  
Shichuan Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fly Ash ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Friction Angle ◽  
Coal Gangue ◽  
Cemented Paste Backfill ◽  
Paste Backfill

Cemented paste backfill containing coal gangue and fly ash (CGFACPB) is an emerging backfill technique for coal mines that allows environmentally hazardous coal gangue and fly ash to be reused in the underground goaf. Meanwhile, CGFACPB can provide an efficient ground support and reduce the surface subsidence. Due to the difference of consolidation environment between the laboratory and the field, the mechanical properties of the cemented paste backfill vary significantly. In this paper, the core specimens were collected from an underground coal mine where the CGFACPB was used for coal mining, and the mechanical properties of the collected specimens were investigated. The cores were obtained from the underground coal mine, and then the standard cylinders or discs were prepared in laboratory. The uniaxial compressive strength (UCS), Young’s modulus, and Poisson’s ratio were determined by the compression tests, and the tensile strength was achieved by the Brazilian test. Then the internal friction angle and cohesion were calculated using the improved Mohr–Coulomb strength criterion. The results showed the development of UCS can be divided into four stages, and the final long-term stable value was about 5.1 MPa. The development of Young’s modulus had similar trend. Young’s modulus had a range from 550 MPa to 750 MPa and the mean value of 675 MPa. Poisson’s ratio gradually increased with the underground curing duration and eventually approached the stable value of 0.18. The failure type of compression samples was mainly single-sided shear failure. The development of tensile strength can be divided into two stages, and the stable value of the tensile strength was about 1.05 MPa. The development of cohesion can be divided into four stages, and the stable value was about 1.75 MPa. The stable value of the internal friction angle was about 25°. This study can provide significant references for not only the long-term stability evaluation of CGFACPB in the field but also the design of optimal recipe of the cemented paste backfill (CPB).

scholarly journals Development of Coal Mine Filling Paste with Certain Early Strength and Its Flow Characteristics

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Feng Zhang ◽  
Jinxiao Liu ◽  
Haiming Ni ◽  
Wenxin Li ◽  
Yongle Liu
Keyword(s):  
Fly Ash ◽  
Coal Mine ◽  
Setting Time ◽  
Flow Characteristics ◽  
Coal Gangue ◽  
Practical Significance ◽  
Range Analysis ◽  
Factors Affecting ◽  
Early Strength ◽  
Backfill Strength

In coal mine paste filling technology, geomaterials like coal gangue and fly ash are used as the main component, and cement is applied as the cementing material. In the mining production, mining-and-filling is a cyclic work, where the filling immediately after mining and mining immediately after filling. Long solidification time after filling will affect mining; consequently, the paste should have early strength. In addition, the prepared paste will be conveyed to goaf through the pipeline. The paste flow characteristics will change to some extent in the conveying process, and there is uncertainty about whether the paste can meet the requirements of pumpability and strength. Therefore, the influence of pipeline conveying on flow characteristics of paste before filling the goaf should be taken into consideration. Based on the above two points, this paper studies the paste strength, backfill strength, and pumpability parameters in coal mine paste filling and determines the early and later strength of coal mine paste, as well as the pumpability parameters such as slump degree, segregation degree, setting time, and paste gradation. With the determined mass proportion of coal gangue, fly ash, and silicate cement, the orthogonal test was carried out with three factors including gypsum content, the content of early strength agent (Na2SO4), and the mass concentration, and at three levels. The factors affecting paste flow characteristics were determined by range analysis, and the factors affecting the paste’s early strength were determined by the XRD test and SEM test on its microstructure. With paste proportioning and pipeline conveying simulation system, taking slump, segregation degree, backfill strength, and other parameters as indicators, we obtain the influence law of pipeline conveying on the flow characteristics of paste. The research has great theoretical and practical significance for developing coal paste with early strength and its flow characteristics.

scholarly journals Strength and Weakness Characteristics of Using Polymer Based Alternative to Steel Mesh In Underground Coal Mine Strata

2019 ◽  
Vol 2 (1) ◽  
pp. 37
Author(s):  
Akash Talapatra
Keyword(s):  
Mechanical Properties ◽  
Physical Properties ◽  
Coal Mine ◽  
Underground Coal Mine ◽  
Elongation At Break ◽  
Steel Mesh ◽  
Mesh Material ◽  
Underground Roadway ◽  
Roadway Support ◽  
Break Yield

Nowadays a viable development of polymer based material as an alternative to the steel mesh material has been increased at a notable amount for providing enough support in the underground roadways. This feasibility study done on the development of using polymer based alternative is related with both of the chemical & physical properties of the selected material. If the polymer alternative has a considerable amount of capability to tolerate all the physical & material constraints equal to or above the normal steel mesh, then the possibility of using polymeric alternatives have been increased at a greater extent. For this reinforcement test, an experiment practice would be done by comparing the mechanical properties of the steel mesh with the polymeric material such as modulus property, elongation-at-break, yield stress etc. After that, a suitable polymer based alternative will be applied for underground roadway support in upcoming days.

The application of ultra-fine fly ash in the seal coating for the wall of underground coal mine

2016 ◽  
Vol 27 (4) ◽  
pp. 1645-1650 ◽  
Author(s):  
Huiping Song ◽  
Jianqiang Liu ◽  
Fangbin Xue ◽  
Fangqin Cheng
Keyword(s):  
Fly Ash ◽  
Coal Mine ◽  
Underground Coal Mine

Experimental Study on the Compression Rebound Modulus of Coal Gangue Mixture

2012 ◽  
Vol 608-609 ◽  
pp. 1759-1763
Author(s):  
Xian Hai Xu ◽  
Ya Peng Zhang ◽  
Zhi Fei Zhang ◽  
Ju Jun Zhang
Keyword(s):  
Experimental Study ◽  
Regression Analysis ◽  
Fly Ash ◽  
Coal Mine ◽  
Uniform Design ◽  
Regression Equation ◽  
Coal Gangue ◽  
Analysis Model ◽  
Mix Proportion ◽  
Cement Mixture

This experiment was designed by making a coal gangue with coal gangue, fly ash, lime power and a small amount of cement mixture selected from Dongpang coal mine in Hanxing area.We tested the compressive rebound modulus strength of the mixture, and according to the method of uniform design, 8 groups mix ratio were designed and the experiments on the coal gangue mixture in various mix proportion have been conducted. The experimental results were analyzed by regression analysis model, and the regression equation between the compression rebound modulus of coal gangue mixture and the blending amount of each admixture was established. Finally, using this regression analysis model, the influence of the fly ash, calces, cement to strength on the compression rebound modulus of coal gangue mixture was analyzed.

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

Energies ◽  
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.

scholarly journals Monitoring and Assessment of Cemented Paste Backfill Containing Coal Gangue and Fly Ash in an Underground Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xinguo Zhang ◽  
Jinhai Zhao ◽  
Lin Xin ◽  
Kun Wang ◽  
Haiyang Pan
Keyword(s):  
Fly Ash ◽  
Monitoring System ◽  
Field Monitoring ◽  
Surface Subsidence ◽  
Coal Gangue ◽  
Longwall Face ◽  
Curing Temperature ◽  
Deformation Stage ◽  
Paste Backfill ◽  
Stable Stage

Cemented coal gangue paste backfill (CCGPB) containing coal gangue and fly ash is a backfilling technique newly developed in coal mines in China that allows environmentally hazardous products, such as gangue and fly ash, to be reused in underground stopes. CCGPB materials provide efficient ground support for the caving of strata and reduce surface subsidence. In this paper, field monitoring of CCGPB properties was conducted in an underground coal mine, which mainly included the measurement of the longwall face temperature, humidity, CCGPB internal hydration temperature, stress conditions inside the backfills, and displacement. First, the components of the backfills, paste technique, slurry generation procedures, coalfield geology, and mining conditions were introduced. Then, a monitoring system was designed in the field. An online monitoring system was installed. The results of the field monitoring showed that the curing temperature significantly varied, i.e., from 26°C near the main gate to 37°C near the tailgate. The curing humidity had the same trends, increasing from 60% relative humidity (RH) near the main gate to 81% RH near the tailgate. The internal hydration process of the paste was divided into four stages, i.e., the rapid hydration stage, slower hydration stage, rapid decline hydration stage, and relatively stable stage. The highest hydration temperature was 50°C, which was measured on the second day after the backfill process. The temperature approached stability at 41°C. The evolution of the roof stress applied on the CCGPB was divided into four stages: the development stage, regulation stage, rapid growth stage, and relatively stable stage. The maximum roof loading was 12 MPa in the middle of the longwall face. The deformation of the backfill experienced four stages, i.e., the rapid deformation stage, slow deformation stage, relatively stable stage, and long-term stable stage. The maximum deformation was 104.3 mm, appearing in the middle of the face. In addition, the compression ratio of the backfill was approximately 4%. The results of this study showed that the working conditions of backfills in the field were different from those in the laboratory. This paper provides guidance for the design of the CCGPB technique and the predictions of surface subsidence induced by the production process of underground mining.

scholarly journals Mechanical Properties of Furnace Slag and Coal Gangue Mixtures Stabilized by Cement and Fly Ash

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7103
Author(s):  
Hongbo Li ◽  
Hubiao Zhang ◽  
Pengfei Yan ◽  
Changyu Yan ◽  
Yufei Tong
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Unconfined Compressive Strength ◽  
Cement Content ◽  
Peak Stress ◽  
Coal Gangue ◽  
Replacement Rate ◽  
Splitting Strength ◽  
The Relationship

The mechanical properties and strength formation mechanism of cement–fly-ash-stabilized slag–coal gangue mixture were examined using an unconfined compressive strength test, splitting strength test, triaxial test, and scanning electron microscopy to solve the limitations of land occupation and environmental pollution that is caused by fly ash from the Xixia District thermal power plant in Yinchuan, slag from the Ningdong slag yard, and washed coal gangue. Its performance as a pavement base mixture on the road was investigated. The results demonstrated that as the slag replacement rate increased, the maximum water content increased while the maximum dry density decreased. The addition of slag reduced the unconfined compressive strength and splitting strength of the specimens; furthermore, the higher the slag substitution rate, the lower the unconfined compressive strength and splitting strength of the specimens. As the cement content increased, the specimen’s unconfined compressive strength increased. Based on the principle of considering the mechanical properties and economic concerns, the slag replacement rate in the actual construction should be ~50% and should not exceed 75%. Based on the relationship between the compressive strength and splitting strength of ordinary concrete, the relationship model between the unconfined compressive strength and splitting strength of cement–fly-ash-stabilized slag–coal gangue was established. The failure mode, stress–strain curve, peak stress, and failure criterion of these specimens were analyzed based on the triaxial test results, and the relationship formulas between the slag substitution rate, cement content, peak stress, and confining pressure were fitted. As per the SEM results, the mixture’s hydration products primarily included amorphous colloidal C-S-H, needle rod ettringite AFt, unhydrated cement clinker particles, and fly ash particles. The analysis of the mixture’s strength formation mechanism showed that the mixture’s strength was the comprehensive embodiment of all factors, such as the microaggregate effect, secondary hydration reaction, and material characteristics.

scholarly journals Preparation of Green Low Strength Mixture for Foundation Reinforcement Treatment by Using Fly Ash and Waste Coal Gangue

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 664 ◽  
Author(s):  
Linhao Li ◽  
Guangcheng Long ◽  
Kunlin Ma ◽  
Hongwei Ma ◽  
Wenbing Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
High Performance ◽  
Acid Resistance ◽  
High Volume ◽  
Waste Recycling ◽  
Coal Gangue ◽  
Dynamic Shear Modulus ◽  
Durability Performance

Effective foundation reinforcement treatment is essential for modern large and complex infrastructure, while it is significant for developing new green high-performance materials for foundation reinforcement. This study investigates a new green concrete by using high volume fly-ash and coal gangue aggregates, which is expected to apply for foundation treatment of modern infrastructure with high loading-bear ability. In this experiment, 12 mix proportions of fly ash coal gangue mixture (the material name, abbreviated FGM) were designed, and its mechanical properties and durability performance were investigated. The mechanical properties of FGM include compressive strength, dynamic elastic modulus, dynamic shear modulus, Poisson’s ratio, and the stress–strain behaviors. The durability performance was evaluated by the parameters of acid resistance, which simulated an acid circumstance. After that, the environmental effects about carbon emission of this material were also investigated. Results show that the FGM with 84.6% wastes utilizing rate is a cost-effective material for foundation reinforcing treatment. Its compressive strength at 28 days and 60 days can reach more than 8 MPa and 10 MPa, respectively. After being immersed in the acid environment for 140 days, the mass loss (%) of the material could be under 3.5%. The greenness shows that the e-CO2 indices of FGM are lower than 20 kg/MPa·m3, and the e-energy indices are at below 150 MJ/MPa·m3. FGM has the advantages of acid resistance, waste recycling, and lower carbon emissions than the previous methods for foundation improvement.

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