Properties and Application of Backfill Materials in Coal Mines in China

Zhang, Jixiong; Meng, Lingkui; Taheri, Abbas; Zhang, Weiqing; Wu, Zhongya; Song, Weijian

doi:10.3390/min9010053

Cited by 74 publications

(43 citation statements)

References 40 publications

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“…A considerable amount of research has recently been conducted on filling materials (coal gangue, fly ash, and construction waste) and microstructural characteristics for coal mines [6][7][8]. Feng et al [9] studied the mechanical properties of cemented filling materials in which gangue was partially replaced by waste concrete.…”

Section: Introductionmentioning

confidence: 99%

Influential Factors in Transportation and Mechanical Properties of Aeolian Sand-Based Cemented Filling Material

Zhou

Ouyang

et al. 2019

Minerals

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Given that normal filling technology generally cannot be used for mining in the western part of China, as it has only a few sources for filling gangue, the feasibility of instead using cemented filling materials with aeolian sand as the aggregate is discussed in this study. We used laboratory tests to study how the fly ash (FA) content, cement content, lime–slag (LS) content, and concentration influence the transportation and mechanical properties of aeolian-sand-based cemented filling material. The internal microstructures and distributions of the elements in filled objects for curing times of 3 and 7 days are analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The experimental results show that: (i) the bleeding rate and slump of the filling-material slurry decrease gradually as the fly ash content, cement content, lime–slag content, and concentration increase, (ii) while the mechanical properties of the filled object increase. The optimal proportions for the aeolian sand-based cemented filling material include a concentration of 76%, a fly ash content of 47.5%, a cement content of 12.5%, a lime–slag content of 5%, and an aeolian sand content of 35%. The SEM observations show that the needle/rod-like ettringite (AFt) and amorphous and flocculent tobermorite (C-S-H) gel are the main early hydration products of a filled object with the above specific proportions. After increasing the curing time from 3 to 7 days, the AFt content decreases gradually, while the C-S-H content and the compactness increase.

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Section: Introductionmentioning

confidence: 99%

Influential Factors in Transportation and Mechanical Properties of Aeolian Sand-Based Cemented Filling Material

Zhou

Ouyang

et al. 2019

Minerals

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“…The dense population and high degree of urbanization in Central and Eastern China have created an increased demand for land for urban constructions and farming in recent years. Furthermore, these regions are important coal production centers and home to many goafs [1][2][3][4]; these goafs further strain the availability of useful land for urbanization and farming. Therefore, one effective way to address this situation might be to stabilize collapsing mines to improve their load-bearing capacities to make them suitable sites for building construction [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…At present, strengthening a foundation is fundamental to solving the problem of instability of buildings constructed on restored mined-out lands [10][11][12]. This objective is generally achieved by filling goafs with cemented material, high-water-content materials, or granular materials [2]. It is more reliable and safer to fill goafs with cemented materials than with granular materials to make them conform to the stability requirements for construction.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Characteristics and Failure Prediction of Cement Mortar with a Sandwich Structure

Liu

Tan

et al. 2019

Minerals

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It is necessary to master the mechanical properties and failure prediction of the composite of mortar and rock block in a mined-out area. In this study, uniaxial compression and acoustic emission (AE) synchronous tests of mortar specimens with different sandwich materials and cement–sand ratios were carried out. The results showed that the compressive strength and elastic modulus of mortar specimens increased with an increase in the cement–sand ratio and the stiffness of the sandwich material. The AE counts and energy of mortar specimens with a high-stiffness sandwich material were maximum when they were destroyed. The b value, a number that reflects the extent of fracture propagation, decreased first and then increased with the increase in strain. The inflection point of the b value can be taken as the indication of the imminent failure of the mortar. A method for determining the b value at the turning point was proposed and verified.

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“…In China, backfilling mining has made great achievements, including gangue backfilling material, cemented paste material and high-water-content materials [1][2][3][4]. Meanwhile, retained gob-side entry (RGE) is a significant development for longwall mining without leaving gate pillar unmined.…”

Section: Introductionmentioning

confidence: 99%

Vertical Stress and Deformation Characteristics of Roadside Backfilling Body in Gob-Side Entry for Thick Coal Seams with Different Pre-Split Angles

et al. 2019

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Retained gob-side entry (RGE) is a significant improvement for fully-mechanized longwall mining. The environment of surrounding rock directly affects its stability. Roadside backfilling body (RBB), a man-made structure in RGE plays the most important role in successful application of the technology. In the field, however, the vertical deformation of RBB is large during the panel extraction, which leads to malfunction of the RGE. In order to solve the problem, roof pre-split is employed. According to geological conditions as well as the physical modeling of roof behavior and deformation of surrounding rock, the support resistance of RBB is calculated. The environment of surrounding rock, vertical stress and vertical deformation of the RBB in the RGE with different roof pre-split angles are analyzed using FLAC 3D software. With the increase of roof pre-split angle, the vertical stresses both in the coal wall and RBB are minimum, and the vertical deformation of RBB also decreases from 110.51 mm to 6.1 mm. Therefore, based on the results of numerical modeling and field observation, roof pre-split angle of 90 • is more beneficial to the maintenance of the RGE.Energies 2019, 12, 1316 2 of 16 deformation. Using the numerical simulation, break position and shape of the main roof along the RGE, the influence of different support methods on the roof movement and the relevant technical parameters of RBB were analyzed [18,19]. Tan et al. (2015) studied the stability of RBB under hard roof condition by using flexible-hard support model for RGE [20]. Zhang et al. (2015) analyzed high-water packing materials in RGE using numerical analysis, and the optimal width of the RBB was analyzed [21].There are also many studies involving problems in using the technology, such as serious deformation of RBB [22][23][24]. Using the dynamic analysis software LS-DYNA (Livermore Software Technology Corporation, Livermore, CA, USA) and theoretical analysis, Gao et al. (2013) analyzed the pressure relief mechanism of the induced roof caving by deep-hole blasting. It was found that the deep-hole-blasting can effectively reduce the load transferred to RBB and is more conducive to the maintenance of RGE [25]. Zhao et al. (2015) proposed the optimal control technology of surrounding rock structure through the following methods. First, the hard roof ahead of the working face is pre-split using deep holes. Then overhanging roof at gob side is broken so as to release the pressure by deep-hole blasting. The control technology has been successfully applied in Pingdingshan No. 12 coal mine [26]. Sun et al. studied the key parameters including height, angle, and length of deep-holes for roof breakage and pressure relief [27].However, most studies on RGE are against thin coal seam mining. It has been shown that RGE can achieve good results in thin coal seams. However, in thick coal seams using the fully mechanized longwall top coal caving (FMLTCC), the situation of the RBB is quite different. In this paper, using FLAC 3D (Itasca: Minneapolis, MN, USA), vert...

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Properties and Application of Backfill Materials in Coal Mines in China

Cited by 74 publications

References 40 publications

Influential Factors in Transportation and Mechanical Properties of Aeolian Sand-Based Cemented Filling Material

Influential Factors in Transportation and Mechanical Properties of Aeolian Sand-Based Cemented Filling Material

Mechanical Characteristics and Failure Prediction of Cement Mortar with a Sandwich Structure

Vertical Stress and Deformation Characteristics of Roadside Backfilling Body in Gob-Side Entry for Thick Coal Seams with Different Pre-Split Angles

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