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Field and experimental research on airflow velocity boundary layer in coal mine roadway

Luo Yonghao, Zhang Yangsheng

Archives of Mining Sciences

2020

Vol. 65, no. 2

255--270

There is an airflow velocity boundary layer near tunnel wall when the air is flowing in the underground coal mine. The thickness and distribution of the airflow velocity boundary layer could influence the discharge of harmful and toxic gases that enter the ventilating airflow through this flow interface. It may also have a major impact in coal mine gas explosion. The results of field measurements and simulation experimental data are used to research airflow velocity boundary layer in a flat walled mine roadway, which is considered in turn: as unsupported, I-steel sectioned arch or bolted and shot create supported cross section. By referenced to other literature studies that consider boundary layer characteristics and the analysis of on-site and experimental data sets we obtain the corresponding airflow velocity boundary layer characteristics for each of the supported roadway sections. The airflow velocity within the boundary layer increase is assumed to follow a logarithmic law given by the expression: u = a Ln(x) + b. It is concluded that the thickness of the airflow velocity boundary layer is observed to significantly decrease with the airflow center velocity and to increase with roadway wall roughness. The airflow velocity distribution is found to be described by the equation: u = (m1v + n1)Ln(d) + m2v + n2, for the three types coal mine tunnel taking into account the influence of center airflow velocity.

Study of inorganic powders used for preparation of waterproof coating to coal mine roadways

Song H., Liu J., Xue F., Cheng F.

Polimery

2016

T. 61, nr 11-12

844--849

The new coatings based on styrene-acrylate copolymer with solid powder additives were prepared. Solid additives were one of three types of adhesives (white cement, Portland cement, and alumina cement) and one of four inorganic fillers (quartz powder, talcum powder, calcium carbonate powder, and fly ash). The coatings were tested by determination of surface drying time, hard drying time, tensile strength, and elongation at break. The ratio of water absorption after 7 days was also measured. The results showed that white cement was the best inorganic adhesive with optimal amount of 40–50 wt % in solid powder part. Quartz powder served as better inorganic filler compared with talcum powder and calcium carbonate powder. Fly ash could also be used as good inorganic filler but in amount lower than 10 wt %. Thus prepared coatings satisfy requirements for class III according to GB/T23445-2009 standard.

Przygotowano nowe powłoki na bazie kopolimeru styren-akrylan z dodatkiem proszków stałych. Dodatki stałe stanowiły jeden z trzech rodzajów spoiwa (cement biały, cement portlandzki i cement glinowy) oraz jeden z czterech napełniaczy nieorganicznych (kwarc w postaci proszku, talk, sproszkowany węglan wapnia oraz popiół lotny). Powłoki badano przez określanie czasu suszenia powierzchni, czasu całkowitego suszenia, wytrzymałości na rozciąganie i wydłużenia przy zerwaniu. Wyznaczano również współczynnik absorpcji wody po 7 dniach. Badania wykazały, że najlepszym spoiwem nieorganicznym jest cement biały wilości 40–50 % mas. Proszek kwarcowy jest lepszym napełniaczem nieorganicznym niż talk lub sproszkowany węglan wapnia. Stwierdzono również, że dobrym napełniaczem nieorganicznym są popioły lotne, ale mogą być stosowane tylko w ilości mniejszej niż 10 % mas. Tak przygotowane powłoki spełniają wymagania klasy III według normy GB/T 23445-2009.