open access

https://hdl.handle.net/2115/66650

Effect of Humidity on Tensile Strength of Rocks in Selected Underground Coal Mines in Malawi

英語

Malawi

2017-06-27

American Rock Mechanics Association

Proceedings of US Rock Mechanics/Geomechanics Symposium 2017 (ARMA 2017)

ARMA 17-0217

One of the major challenges facing coal mines in Malawi is occurrence of hanging roof falls during the rainy season. Following this, the effect of humidity on the tensile strength of coal bearing rocks, arkose sandstone and fine-grained sandstone from Mchenga underground coal mine, was studied aiming to clarify the mechanism of roof fall in the underground mines and proposing countermeasures against the roof falls. Rock samples from the mine were treated in varying humidity levels. Some specimens were oven dried at 80C and a desiccant was used to attain low humidity. Moderate humidity was obtained using magnesium-nitrate-hexahydrate, high humidity was achieved by pure water and some specimens were vacuum saturated. Subsequently, Brazilian test was carried out to obtain indirect tensile strength along the sedimentary plane. For comparison, Neogene tuffaceous Kimachi sandstone from Japan was also tested, following the same conditions. It was confirmed that indirect tensile strength of the rocks decreased with increase in humidity. The sensitivity of indirect tensile strength to humidity for arkose and fine grained sandstones was 12% or 29% larger than that for Kimachi sandstone. The stronger sensitivity for Mchenga roof rocks would be because the rocks contain illite, whose strength is very sensitive to water, while Kimachi sandstone contains only less sensitive zeolite for clay minerals.

会議発表論文

Accepted Manuscript

Copyright 2017 ARMA, American Rock Mechanics Association This paper was prepared for presentation at the 51st US Rock Mechanics / Geomechanics Symposium held in San Francisco, California, USA, 25-28 June 2017.