Zhang, Y., et al. INFLUENCE OF TEMPERATURE ON PHYSICAL AND MECHANICAL PROPERTIES OF A SEDIMENTARY ROCK Coal Measure Mudstone by Yuan ZHANG a,b* , Zhijun WAN a,b , John MCLENNAN c , Bin GU b , and Xupeng TA b a Key Laboratory of Deep Coal Resource Mining, China University of Mining and Technology, Ministry of Education, Xuzhou, Jiangsu, China b School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu, China c Energy and Geoscience Institute, University of Utah, Salt Lake City, Ut., USA Original scientific paper https://doi.org/10.2298/TSCI190101297Z Determining the physical and mechanical behavior of sedimentary rocks is one of the most common challenges in deep rock mass engineering. Experiments were con- ducted to study the physical and mechanical properties of coal measure mudstone with SEM, XRD, and uniaxial compression testing. The results show that tempera- ture has a significant effect on the physical and mechanical properties of coal meas- ure mudstone. The presence of clay minerals in the evaluated mudstone contributes to the unique characteristics seen at high temperature. The mudstone experiences obvious color changes on the surface as temperature rises. This is mostly attributed to the iron-bearing clay minerals. Internal color change is caused by thermal de- composition of kerogen associated with the clay minerals. As the major clay mineral in mudstone, kaolinite undergoes significant phase changes at high temperatures, which leads to changes in mechanical properties. From 25 °C to 200 °C, due to the evaporation of absorbed water from the clay minerals, the strength of the mudstone increases significantly. As the temperature continues to rise beyond this, water evaporation continues and the rock strength increases gradually from 200 °C to 400 °C. When the temperature reaches 400 °C, this mudstone was strengthened as a result of decomposition of the kaolinite and thermal expansion of crystalline min- erals. Above 600 °C, dehydration of the clay minerals ends while thermal cracking initiates gradually, which results in decreasing strength. Key words: rock mechanics, mechanical property, coal measure mudstone, high temperature Introduction Currently, humans have been able to exploit solid mineral resources at depths to around 4 km, and drilling has reached strata of more than 10 km [1, 2]. Generally, deep rocks are in a high temperature environment, which may affect their physical and mechanical prop- erties. Deep rock mass engineering, such as underground coal gasification, geothermal energy exploitation, underground nuclear waste storage, and rock mass support of tunnels after fire, all involve high temperature rocks. The temperature ranges from normal temperatures (10-50 °C) to extreme temperatures (1000-1500 °C) in these rocks [3]. Consequently, research related to –––––––––––––– * Corresponding author, e-mail: [email protected]
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Zhang, Y., et al.
INFLUENCE OF TEMPERATURE ON PHYSICAL
AND MECHANICAL PROPERTIES OF A SEDIMENTARY ROCK
Coal Measure Mudstone
by
Yuan ZHANG
a,b*
, Zhijun WAN
a,b
, John MCLENNAN
c
,
Bin GU
b
, and Xupeng TA
b
a Key Laboratory of Deep Coal Resource Mining, China University of Mining and Technology,
Ministry of Education, Xuzhou, Jiangsu, China b School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu, China
c Energy and Geoscience Institute, University of Utah, Salt Lake City, Ut., USA
Original scientific paper https://doi.org/10.2298/TSCI190101297Z
Determining the physical and mechanical behavior of sedimentary rocks is one of the most common challenges in deep rock mass engineering. Experiments were con-ducted to study the physical and mechanical properties of coal measure mudstone with SEM, XRD, and uniaxial compression testing. The results show that tempera-ture has a significant effect on the physical and mechanical properties of coal meas-ure mudstone. The presence of clay minerals in the evaluated mudstone contributes to the unique characteristics seen at high temperature. The mudstone experiences obvious color changes on the surface as temperature rises. This is mostly attributed to the iron-bearing clay minerals. Internal color change is caused by thermal de-composition of kerogen associated with the clay minerals. As the major clay mineral in mudstone, kaolinite undergoes significant phase changes at high temperatures, which leads to changes in mechanical properties. From 25 °C to 200 °C, due to the evaporation of absorbed water from the clay minerals, the strength of the mudstone increases significantly. As the temperature continues to rise beyond this, water evaporation continues and the rock strength increases gradually from 200 °C to 400 °C. When the temperature reaches 400 °C, this mudstone was strengthened as a result of decomposition of the kaolinite and thermal expansion of crystalline min-erals. Above 600 °C, dehydration of the clay minerals ends while thermal cracking initiates gradually, which results in decreasing strength.
Key words: rock mechanics, mechanical property, coal measure mudstone, high temperature
Introduction
Currently, humans have been able to exploit solid mineral resources at depths to
around 4 km, and drilling has reached strata of more than 10 km [1, 2]. Generally, deep rocks
are in a high temperature environment, which may affect their physical and mechanical prop-
erties. Deep rock mass engineering, such as underground coal gasification, geothermal energy
exploitation, underground nuclear waste storage, and rock mass support of tunnels after fire, all
involve high temperature rocks. The temperature ranges from normal temperatures (10-50 °C)
to extreme temperatures (1000-1500 °C) in these rocks [3]. Consequently, research related to
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