Investigation on relationship of the burial depth and mechanical properties for sedimentary rock
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ORIGINAL PAPER
Investigation on relationship of the burial depth and mechanical properties for sedimentary rock Xuewei Liu 1,2 & Quansheng Liu 3 & Yongshui Kang 1 & Bin Liu 1 Received: 18 November 2019 / Accepted: 29 July 2020 # Saudi Society for Geosciences 2020
Abstract The aim of this study is to correlate the mechanical properties with rock burial depth. For this purpose, a series of sandstone specimens with burial depth varying from 460 to 900 m were collected from the same rock stratum in six coal mines of Huainan coalfield, China. Experimental results indicate that rock mechanical parameters (including tensile strength, uniaxial compressive strength (UCS), elastic modulus, cohesion, and internal friction angle) increase as the specimen burial depth increases. Empirical models describing the relationships between mechanical parameters and burial depth were established. Furthermore, the micromechanism behind the effect of burial depth on strength was investigated via XRD and SEM. The results show that a deeper burial depth is associated with a higher quartz content and a lower porosity. This is caused both by an increased effective stress and by temperature and is related to the secondary diagenesis process, which can result in increase in UCS and tensile strength. Finally, the empirical models were validated by four specimens with different burial depths. Keywords Sedimentary rock . Micro-mechanism . Strength parameters . Variability with depth . Mineral composition and porosity
Introduction As it is widely known, coal resources are gradually being depleted due to the development of the economy, and the mining depth is growing deeper. Especially in China, over 50% of coal resources are found at depths of at least 1000 m, and the mining depth is increasing at an annual rate of ~ 10–25 m. This increased mining depth causes an increase in gravity stress, temperature, water pressure, and deformation, which have significant influence on the stability of
Responsible Editor: Zeynal Abiddin Erguler * Xuewei Liu [email protected] 1
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China
2
Department of Civil Engineering, Monash University, Clayton, VIC, Australia
3
The key laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province, School of Civil Engineering, Wuhan University, Wuhan, China
roadway (Liu et al. 2019, 2020). Therefore, it is important to study rock strength characteristics in deep mining environments. In recent years, the mechanical properties of intact rock have been widely studied. One major topic of investigation has been the rock strength under different extrinsic conditions, such as thermal (Peng et al. 2016; Tang et al. 2019a), fluid saturation (Li and Wang 2019; Tang et al. 2019b), stress state (Liu et al. 2018, 2019b; Yang et al. 2019; Meng et al. 2020), freeze (Huang et al. 2019), and multi-field coupling (Liu et al. 2019a; Meng et al. 2019). Based on experimental results,
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