Experimental study of strength characteristics of coal specimens after water intrusion
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ORIGINAL PAPER
Experimental study of strength characteristics of coal specimens after water intrusion Qiangling Yao & Xuehua Li & Jian Zhou & Minghe Ju & Zhaohui Chong & Bin Zhao
Received: 6 June 2014 / Accepted: 19 December 2014 # Saudi Society for Geosciences 2015
Abstract We carried out uniaxial compressive experiments on coal specimens with different moisture contents to gain a better understanding of the water-induced weakening characteristics of coal. The effects of moisture content on the strength and deformation characteristics of the specimens were analyzed. The results of the uniaxial compressive experiment demonstrate that the full stress–strain curve presents plastic deformation characteristics with the increase of the moisture content in the coal specimens. A positive linear relation between the peak strain and moisture content and a negative one between the compressive strength and moisture content were observed. The results also show that the elastic modulus and the moisture content satisfy a negative exponential function. Taking the obtained relation as boundary conditions and applying the statistical damage theory and strain equivalence hypothesis, we derived a statistical constitutive damage model for coal which can reflect the effects of the moisture content. Keywords Coal specimens . Moisture content . Strength reduction . Failure forms . Damage variable
Introduction Water–rock interaction is an important yet challenging issue in engineering rock mechanics. Knowledge and understanding Q. Yao : X. Li (*) : J. Zhou : M. Ju : Z. Chong School of Mines, China University of Mining and Technology, Xuzhou 221008, China e-mail: [email protected] Q. Yao : X. Li : J. Zhou : M. Ju : Z. Chong Key Laboratory of Deep Coal Resource Mining (CUMT), Ministry of Education, Xuzhou 221008, China B. Zhao Huainan Mining Industry Group, Huainan 232001, China
of the mechanisms of the interaction between water and rock and its effects on rock properties is of great importance in mining engineering. The presence of water in underground coal mine sites such as roadways, coal pillars, and chambers is a significant problem and requires further study. Numerous studies have demonstrated that water has a significant impact on the strength and deformation of rock (Lin et al. 1998; Tang et al. 2002; Vasarhelyi and Van 2006; Erguler and Ulusay 2009; Liu et al. 2009). Water can affect the mechanical properties of various types of rock (Parate 1973; Broch 1979; Masuda 2001), particularly sedimentary rocks (Afrouz and Harvey 1974; Van Eeckhout 1976; Vasarhely 2005) which are commonly found in underground coal mines. Therefore, a good understanding of water–rock interaction is vital during the design and construction of underground projects. For this purpose, various studies were carried out, e.g., Rao et al. (1987), Li and Reddish (2004), Fahimifar and Soroush (2007), Yilmaz (2010), and Hu et al. (2014). Previous results have shown that up to 90 % of the unconfined compressive strength of rock can be lost at approximately one t
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