Experimental Study of Slurry Flow in Mining-Induced Fractures during Longwall Overburden Grout Injection

Xuan, Dayang; Li, Jian; Zheng, Kaidan; Xu, Jialin

doi:10.1155/2020/8877616

“…Traditionally, the slurry used in the overburden isolated grouting project is made of fly ash particles mixed with water [20]. The diffusion radius and thickness distribution of the fly ash slurry have been discussed in previous studies.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Diffusion Radius of Modified Slurry Used in Longwall Overburden Isolated Grouting

Xuan

¹

,

Zhang

²

,

Li

³

et al. 2023

Geofluids

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The slurry diffusion radius is an important parameter in grouting engineering. In some cases, injection into partial overburden is needed in grouting engineering, and it is thus critical to control the slurry diffusion so as to reduce unnecessary grout take. In an effort to solve such issues in longwall overburden grouting, we proposed the addition of cement as a means of modifying fly ash slurry in order to reduce grout diffusion and grout take. The characteristics of the modified slurry were determined under different water-ash ratios and cement-blending ratios. The cement-blending ratio was found to have a small effect on the density of the slurry but a significant effect on the slurry’s precipitation rate and viscosity. The slurry diffusion experimental system was established to study the diffusion radius and consolidation. Results for both the fly ash slurry and the modified slurry revealed a circular diffusion pattern centered around the grouting borehole. The diffusion radius of the modified slurry made with 10% cement was 19.4% lower than that of the fly ash slurry, but its solidification thickness appeared to increase. The modified slurry diffusion had a two-stage effect: a “stability control stage” and a “consolidation control stage.” In the consolidation control stage, the diffusion radius of the modified slurry was smaller than that of the fly ash slurry, and this stage was the key to control the diffusion radius of the slurry. Field trials were conducted based on the results of the study, and grout take was reduced effectively. This research provides a theoretical basis for slurry diffusion radius control in longwall grouting.

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“…High water resistance materials with sand, paraffin, calcium carbonate, petroleum jelly, and gypsum as raw materials have been used to simulate the waterproof layer (Lian et al, 2015). They are used as water-proof materials with low water permeability to simulate the slurry diffusion law at the non-pressure stage (Li J et al, 2020) and the longwall overburden isolated grout injection (Xuan et al, 2020). Polyvinyl alcohol (PVA) is added with river sand, paraffin wax, talcum powder, hydraulic oil, and straw to adjust the permeability.…”

Section: Introductionmentioning

confidence: 99%

“…Although grouting could be realized, the slurry water bleeding and seepage of grouting injection could not be realized. With technological improvements, a visual experimental system that can simulate the flow of IOGI was established (Li J et al, 2020;Xuan et al, 2020). Although this system can more adequately respond to the actual slurry diffusion, slurry diffusion studies were performed under the condition of predefined regular injection space.…”

Section: Introductionmentioning

confidence: 99%

Experimental method and application of the slurry “diffusion-bleeding-seepage” of isolated overburden grout injection

Wang

¹

,

Xu²,

Xuan³

et al. 2023

Front. Earth Sci.

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Isolated overburden grout injection (IOGI) is a green mining method to control surface subsidence. Slurry water significantly influences grouting effectiveness and mining safety. This study establishes a three-dimensional visualization experimental system for slurry “diffusion-bleeding-seepage” to investigate the seepage law of slurry water. The system is composed primarily of a transparent box (1.2 m × 0.5 m × 0.25 m) and support, with the solid–liquid coupling seepage similar material and modules for mining, grouting injection, slurry pressure and displacement monitoring, overburden saturation monitoring, and water leakage monitoring of the working face. A similar material with good permeability and non-disintegration is obtained by hydrophilic, water absorption, and permeability tests. Grouting and mining are simulated by pulling acrylic sheets and pumping slurry. With the fly ash slurry entering the injection layer, the slurry undergoes water–cement separation, and the water bleeding is formed to seep into the similar material. The volumetric water content of the similar material is obtained by arranging multiple groups of volumetric water content sensors into the similar material. The corresponding saturation is obtained by theoretical calculation. The experimental system is used to simulate the seepage of slurry water in a high initial saturation overburden, and the characteristics of injection slurry diffusion and water bleeding are obtained. The profile distribution of seepage of slurry water is found to possess a semi-elliptical shape. Under the condition of high initial saturation, slurry water appears in the working face. The system provides a convenient method for further research of IOGI slurry water seepage.

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“…Qing-song et al [7] studied the grouting diffusion law of cement-sodium silicate slurry in flowing water, providing valuable insights for guiding the design and construction of grouting to deal with water inrush disasters. Xuan et al [8] designed a set of long-wall overburden grouting visualisation experimental simulation systems to study the flow, pressure distribution, consolidation, and filling thickness of fly ash slurry in rock strata, providing a theoretical basis for the design and optimisation of overburden grouting in underground long-wall mining. Girskas et al [9] studied the effective utilisation of fly ash and demonstrated that this material can inhibit the cement hydration process and can be used to produce cement-based composite materials with better frost resistance and durability.…”

Section: Introductionmentioning

confidence: 99%

Properties and Engineering Applications of a New Goaf Grouting Filling Material

Feng

¹

,

Xia

²

,

Zhang

³

et al. 2022

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In the treatment of goafs in traffic engineering, technical problems such as those related to large-volume grouting and the precise control of material properties are often encountered. To address these issues, we developed a new composite material comprising cement-fly ash-modified sodium silicate (C-FA-MS). The setting time, fluidity, unconfined compressive strength, and microstructure were varied for different proportions of cement-sodium silicate (C-S) slurry, cement-fly ash-sodium silicate (C-FA-S) slurry, and C-FA-MS slurry, and their performances were compared and analysed. The experimental results showed that the initial setting time of the slurry was the shortest when both the original sodium silicate volume ratio ( V S ) and modified sodium silicate volume ratio ( V MS ) were 0.2. The final setting time of the C-S and C-FA-S slurries tended to decrease but then increased with decrease in V S , while that of the C-FA-MS slurry increased with lower V MS . The fluidity of the C-FA-S and C-FA-MS slurries decreased with decrease in V S or V MS at different fly ash admixture ratios. The consolidation compressive strength of C-S increased with decreasing V S , while that of C-FA-S showed a considerable increase only when V S decreased from 0.4 to 0.2. Meanwhile, the compressive strength of the C-FA-MS concretions first increased and then decreased with decrease in V MS . Microstructural analysis revealed that there were more cracks in the C-S agglomerate, the fly ash in the C-FA-S agglomerate reduced the relative density of the skeletal structure, and the stronger cross-linking in the C-FA-MS agglomerate improved the strength of the agglomerate. Under the condition of unit grouting volume, the cost of the C-FA-MS slurry was approximately 44.7% and 31.3% lower than that of the C-S and C-FA-S slurries, respectively. The new C-FA-MS material was applied for the treatment of the goaf in the Wu Sizhuang coal mine. Core drilling detection and audiofrequency magnetotelluric survey revealed that the goaf was sufficiently filled.

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Experimental Study of Slurry Flow in Mining-Induced Fractures during Longwall Overburden Grout Injection

Cited by 16 publications

References 27 publications

Experimental Study on the Diffusion Radius of Modified Slurry Used in Longwall Overburden Isolated Grouting

Experimental Study on the Diffusion Radius of Modified Slurry Used in Longwall Overburden Isolated Grouting

Experimental method and application of the slurry “diffusion-bleeding-seepage” of isolated overburden grout injection

Properties and Engineering Applications of a New Goaf Grouting Filling Material

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