In situ investigations into mining-induced hard main roof fracture in longwall mining: A case study

Yang, Shuai; Wang, Jun; Li, Xuehui; Ning, Jianguo; Qiu, Pengqi

doi:10.1016/j.engfailanal.2019.104188

Cited by 20 publications

(9 citation statements)

References 24 publications

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“…According to longwall observations, the roof pressure acting on the working region is influenced by the main roof behaviour. As a result, whatever the kind of hydraulic support is used, controlling the movement of the main roof is essential [50,51]. The periodic roof weighting is induced by the main roof movement.…”

Section: Main Roof Behaviormentioning

confidence: 99%

Current Theories and Concepts for the Determination of Roof Loading over the Hydraulic Supports in Longwall Faces

Haroon

Heshmat²,

Imbaby³

et al. 2022

Journal of Petroleum and Mining Engineering

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Underground mining of ores affects in-situ rock conditions, resulting in a sequence of strata motions. Roof rock pressure, which is the basis of all ground control issues, is caused by these instabilities. The hydraulic supports are subjected to excessive stress due to the roof rock pressure. The correct forecast of Rock Roof Loading (RRL) provides longwall face stability during ore exploitation, allowing the hydraulic supports to move more freely. This paper presents some of the current theories, approaches, and concepts for the determination of roof loading on longwall faces, with emphasis on the current gaps. This could improve the ability to manage the roof during mining workings, and govern the roof loading conditions and the supporting system. From this study, it can be seen that the periodic weighting of the main roof is an important aspect in the determination of loading requirements. Moreover, many loading calculation methods failed to take into consideration the swelling pressure of immediate roof rocks, and the tilting of the main roof blocks, which exert excessive loads on the supporting systems.

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Section: Main Roof Behaviormentioning

confidence: 99%

Current Theories and Concepts for the Determination of Roof Loading over the Hydraulic Supports in Longwall Faces

Haroon

Heshmat²,

Imbaby³

et al. 2022

Journal of Petroleum and Mining Engineering

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“…By the data fitting process in MATLAB 2012b, the power function was determined to describe D (x) and L (x) as shown in Figures 10 and 11 and equations (4) and (5). e potential dynamic stress R (x) comes from the liberating energy of 2.35 × 10 5 J during the mining-induced fracture of the interactional hard roof structures [9,60]. e effect of this liberating energy on the surrounding rock was replaced with a loading process of the equivalent dynamic stress, and this equivalent dynamic stress was determined as 9 MPa by using the method of elastic deformation energy [61].…”

Section: Layout Of Entrymentioning

confidence: 99%

Method of Entry Layout under Synergistic Effects of Abutment Stress and Dynamic Stress

Shen

Shi

Wang

et al. 2020

Shock and Vibration

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In underground mining engineering, rocks around the entry are always subjected to large plastic deformation disasters, such as supporting body failure, roof rock collapse, and even rock burst under abutment stress and dynamic stress. To improve the stability of these rocks, the entry layout under abutment stress and dynamic stress (ELAD) method was put forward to protect the entry from high abutment stress and dynamic stress. Dynamic disturbance intensity (DDI) was determined as the key evaluation index in ELAD, which was divided into “Slightly Disturbed Type,” “Moderately Disturbed Type,” and “Violent Impact Type” by the dynamic disturbance threshold (DDT) and dynamic large-deformation threshold (DLT). The established servo calculation algorithm was applied into a dynamic and static numerical analysis model with FLAC3D500 software for the solving of DDT and DLT by the method of zero growth DDI of plastic failure zone and the engineering-permitted limitation deformation. This model was validated by comparing the displacement of entry with the measured results in the field. The model results validated that the entry should keep away from the dynamic stress of Violent Impact Type firstly and then be arranged in the zone where the dynamic stress belongs to Slightly Disturbed Type. DDT increases linearly and DLT decreases with a power function as the increasing of the abutment stress. ELAD method is reliable to protect this kind of underground entry and its applicability will be improved by the support resistance by comparing the results from ELAD with those from the widely used methods for field investigation discussion. The analysis procedure can be repeatable and necessary since the rock and coal materials may be different in geological and engineering conditions.

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“…The hard roof structure is frequently encountered in many mining areas. In China, the quantity of coal seams with hard overlying strata accounts for about one third of the total reserves and are distributed in over than 50% of the mining districts (Yang et al, 2019). Datong coalfield is a most typical area characterized by hard roof strata in China (Liu et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Mining-Induced Stress and Ground Pressure Behavior Characteristics in Mining a Thick Coal Seam With Hard Roofs

Zhu

Zhuang³

2022

Front. Earth Sci.

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The hard roof of coal mines has the characteristics of high hardness, good integrity, and large layer thickness, which leads to many ground control problems. To reveal the influence of a hard roof structure on the stress performance and coal pillar stability during mining operations, the 8,104 and 8,105 working faces in the Tongxin coal mine were considered as the research object to analyze the stress behavior during the working face advance. Numerical simulation software FLAC3D was used to establish the numerical model of the longwall face under hard roof conditions. The stress distribution laws and coal pillar stability under different roof strengths were analyzed so as to explain the impacts of the hard roof on the stress distribution at the working face. The results show that during the second face proceeding, the influence zone of the front abutment pressure under hard roof conditions is 6 m wider than that under soft roof conditions, and the bearing stress at the working face is 10.4 MPa higher. At the mining position, the plastic zone of the pillar under hard roof conditions is 11 m wider than that under soft roof conditions, and the peak vertical stress is 5.13 MPa higher than that under soft roof conditions. At 25 m ahead of the working face, the plastic zone of the pillar under hard roof conditions is 6 m wider than that under soft roof conditions, and the peak vertical stress is 24.84 MPa higher than that under soft roof conditions. Additional overburden pressure produced by the uncaved hard roof increased pillar stress and plastic zones. Therefore, the hard roof is the main cause of strong ground pressure behavior in the Tongxin coal mine. Aiming at the strong mine pressure behavior, it is suggested to adopt the pre-splitting technology to reduce the influence of the hard roof on mine pressure.

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In situ investigations into mining-induced hard main roof fracture in longwall mining: A case study

Cited by 20 publications

References 24 publications

Current Theories and Concepts for the Determination of Roof Loading over the Hydraulic Supports in Longwall Faces

Current Theories and Concepts for the Determination of Roof Loading over the Hydraulic Supports in Longwall Faces

Method of Entry Layout under Synergistic Effects of Abutment Stress and Dynamic Stress

Mining-Induced Stress and Ground Pressure Behavior Characteristics in Mining a Thick Coal Seam With Hard Roofs

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