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1

Failure characteristics of W strap in coal mine support

Feng Xiaowei, Xue Fei, Feng Xiaotian, Zhao Tongyang

Archives of Mining Sciences

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2022

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Vol. 67, no. 2

289--302

EN

W strap is a crucial surface support component for underground coal mine roadways. In this study, the failure characteristics of the W strap in the field are discussed, and the loading characteristics of the strap and the faceplate are numerically and experimentally analysed. Afterwards, a loading apparatus capable of reappearing the loading environment of the strap in the field is fabricated. This loading device, combined support systems consisting of a bolt, faceplate and strap is tested under different simulated strata conditions. Failure patterns of the strap are evaluated by the 3D scanning method, and proper selection of a faceplate is explored. Results indicate that a domed faceplate can achieve a favourable supporting effect on strata, and thus it is favoured compared with a square domed faceplate. In addition, rock cavity and rock integrity beneath the strap are essential factors determining the servicing life of the overall supporting system.

2

Criterion for wind environment assessment with consideration to the effect of turbulence

Akahoshi Akinori, Uematsu Yasushi

Technical Transactions

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2019

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Vol. 116, iss. 7

5--22

EN

Turbulence affects the human perception of wind, the wind-induced damage to buildings, the values of wind speeds measured by 3-cup anemometers, and so on. The wind environment assessment criterion proposed by the Wind Engineering Institute Co., Ltd. is based on the relationship between the mean wind speeds measured by 3-cup anemometers and the condition of surrounding terrain. This criterion does not consider the influence of turbulence. Considering the significant urbanization of large cities and the change in anemometers used for wind speed measurements, a new criterion of wind environment assessment that considers the effect of turbulence is required. The present study discusses such a criterion based on a wind tunnel experiment, the observation at various locations, and a questionnaire survey on the wind environment that was conducted with for the residents and pedestrians in Tokyo.

PL

Turbulencja wpływa na postrzeganie wiatru przez człowieka, wywołane wiatrem uszkodzenia budynków, wartości prędkości wiatru mierzone przez anemometry 3-filiżankowe etc. Kryterium oceny środowiska wiatrowego zaproponowane przez Instytut Inżynierii Wiatrowej opiera się na zależności między średnią prędkością wiatru mierzoną przez anemometry 3-filiżankowe a stanem otaczającego deszczu. To kryterium nie uwzględnia wpływu turbulencji. Biorąc pod uwagę znaczną urbanizację dużych miast i zmianę anemometrów używanych do pomiarów prędkości wiatru, wymagane jest nowe kryterium oceny środowiska wiatrowego, które uwzględnia wpływ turbulencji. Niniejszy artykuł omawia takie kryterium oparte na eksperymencie z tunelem aerodynamicznym, obserwacji w różnych miejscach oraz ankiecie dotyczącej środowiska wiatrowego, która została przeprowadzona dla mieszkańców i pieszych w Tokio.

3

Supporting problems at an island mining face in Shanxi, China. Case study based on field observation

Feng Xiaowe

New Trends in Production Engineering

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2019

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Vol. 2, Iss. 1

257--267

EN

In this paper, field observation is conducted in Fujiaao Coal Mine, Linfen city in Shanxi province, China, which is unique because of its island-typed mining layout. Firstly, geology, layout of the coal cutting face, supporting pattern are presented and details are also provided. Then the problems are discussed and analyzed based on existing bolting theories. It finds out the length of the cable bolt is too long, which requires long time to drill boreholes, whilst the effectiveness is limited due to the illogical combination between cable bolt function zone and rock bolt function zone. Also, the face place allocated to rock bolt is very likely to cause line contact between its edge and steel belt, thus the bearing force is tremendously weakened and solely determined by strength of belt. Furthermore, field observation proves the low active supporting effects to roof, thus leading obvious roof sink even without the disturbance of mining activity. Eventually, some solutions are proposed with the intention to improve the situation based on the economic and technical considerations, including bolting in humidity environment, rational cable bolt length, wise choice of face plate, and ways to increase pretension force. The viewpoints and comments of this study can be referred by practitioners in coal mines sharing same difficulties.