Investigation of fill distribution in post-injected longwall overburden with implications for grout take estimation

Xuan, Dayang; Xu, Jialin; Wang, Binglong; Teng, Hao

doi:10.1016/j.enggeo.2016.04.007

Cited by 35 publications

(24 citation statements)

References 23 publications

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“…The thickness was approximately 7 Geofluids 0.53 mm on both sides (and accounted for 5.3% of the mining height), whereas that in the center reached 13.61 mm, and accounted for 86.1% of the mining height. Thus, the thickness of the boundary fill was only 3.8% of that in the center, and the injection fill thickness distribution manifested as half pace, which is consistent with the model as described in [27]. This also indicates that the caved and fractured rocks are further compacted when subjected to the action of grouting pressure, thus allowing a larger injectable space above the isolation layer.…”

Section: Slurry Consolidation and Fill Distributionsupporting

confidence: 84%

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

Xuan

Zheng

et al. 2020

Geofluids

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Slurry flow in mining-induced overburden fractures is an important theoretical concept for the grouting design of longwall overburden grout injection engineering. In this study, a visual experimental simulation system of longwall overburden grouting was designed to study the flow, pressure distribution, consolidation, and fill thickness of fly ash slurry in overburden bedding separation. Experiments showed that the slurry generates a radial and bidirectional flow during nonpressure grouting and presents itself as an approximately elliptical dominant flow channel under pressure injection. This channel expanded horizontally along the strike direction and gradually became tabular. The slurry pressure increased as the grouting time increased. Although the pressure curves at different locations exhibited similar trends, their values did not decrease as the distance from the borehole center decreased during observations. Bleeding and consolidation occurred in the slurry as soon as it flowed out of the borehole to the fracture, and the degree of consolidation increased as a function of the distance from the injection borehole. The bleeding water gathered continually to the boundary of the bedding separation fracture and was then seeped to and stored by the underlying strata based on the injection pressure. The final injection fill is manifested as a half pace with a large thickness at the center. This research provides a theoretical basis for the design and optimization of overburden grout injection in underground longwall mining.

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Section: Slurry Consolidation and Fill Distributionsupporting

confidence: 84%

“…The practical flow radius of a single borehole was determined for longwall overburden injection by using methods of borehole connectivity [21] and borehole imaging [23]. Studies also covered the theoretical model of the final injection fill distribution that was used to estimate the injection ratio [27].…”

Section: Introductionmentioning

confidence: 99%

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

Xuan

Zheng

et al. 2020

Geofluids

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“…Generally, the volume of the void space for the bed separation is presumed to be 30%∼50% of the mined-out coal volume, and the injection ratio is equal to the ratio of the volume of compacted injected fill to the extracted coal seam [40]. In order to estimate the grout takes, the ultimate injection ratio is proposed [40]:…”

Section: Volume Of Void Space and The Grout Takes Estimationmentioning

confidence: 99%

Bed Separation Characteristics of an LTCC Panel and Subsidence Controlling Grouting: Case Study of Longquan Coal Mine, China

Zheng

Zhou

et al. 2022

Shock and Vibration

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The bed separation backfill grouting (BSBG) is commonly used to mitigate the surface subsidence caused by coal mining. The distribution characteristics of bed separation and its dynamic evolving process are crucial for BSBG design. This paper utilizes the continuum-discontinuum element method (CDEM) to study the distribution characteristics of bed separation for a longwall top coal caving (LTCC) panel of Longquan coal mine. Numerical results indicate that in addition to the bed separation below the primary key stratum, several small bed separations may also occurred in the strata between the primary key stratum and the subordinate key stratum. The bed separations in the overburden could be classified into three classes: the upper bed separation, the middle bed separation, and the lower bed separation. The upper bed separation has the longest duration time, and the middle bed separation has the shortest duration time. And the BSBG should be started before the closure of the middle bed separation. Based on the actual geological information, the BSBG scheme for 4203 LTCC panel is proposed to mitigate the surface subsidence by taken the results of numerical simulation into consideration. In addition, the case study of the BSBG is introduced in detail. By using gangue power slurry, BSBG could not only effectively mitigate the surface subsidence but also solve the problems of environmental pollution and land occupation caused by traditional gangue stacking. The present study could provide technical support for surface subsidence mitigation and coal gangue disposal for LTCC mining with similar conditions.

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“…Over the past decades, with coal excavation increased, the social and environmental problem associated mining subsidence in China has become progressively more serious [9][10][11][12] and induced the development of measures to mitigate surface subsidence and improve surface environment, such as strip coal pillar mining, backfilling method, overburden grouting [13][14][15][16], and soil reinforcing [17][18][19]. Overburden grouting method as one of the special mining method is considered to be an effective method to mit-igate overburden failure and control surface subsidence without affecting the subsurface mining [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Calculation of Subsidence due to Longwall Mining with Overburden Grouting and Its Application

Wang

2022

Geofluids

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This paper presents a prediction method of mining-induced surface subsidence due to longwall mining with overburden grouting, which has been proven an effective method to mitigate the overburden failure. This paper proposes a partial overburden grouting (POG) mining method based on surface subsidence basin inversion and innovative longwall panel layout to mitigate overburden failure and subsidence. A prediction model of surface subsidence with overburden grouting, namely, overburden grouting equivalent calculation model (OGECM), is proposed. In this study, an engineering design process and method of POG was established, the strike and dip excavation length and grouting quantity combined as critical indicators for determining the key parameter in surface basin control. In applications at the field grouting test, the surface subsidence characteristics of POG on the side of the opening line of longwall panel were investigated through surface observation station and estimated surface subsidence reduction ratio based on OGECM with grouting compared with those without. The field measurement validated the new subsidence calculation method. POG technology applied to subsidence control has effectiveness in controlling the surface subsidence to less engineering cost but expanding the applications.

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Investigation of fill distribution in post-injected longwall overburden with implications for grout take estimation

Cited by 35 publications

References 23 publications

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

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

Bed Separation Characteristics of an LTCC Panel and Subsidence Controlling Grouting: Case Study of Longquan Coal Mine, China

Calculation of Subsidence due to Longwall Mining with Overburden Grouting and Its Application

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