Abstract
The response of rock mass to engineering activities related to environment greatly depends on the scale of rock mass. Therefore, the scale dependency of rock mechanical behavior under different rock mass conditions is investigated in this research. As a crucial parameter, the volume of the block provides a fundamental understanding to define the rock mass condition and possible mechanical response. In this paper, at first, a systematic approach to calculate the block size distribution (BSD) based on the natural fracture parameters using most suitable distribution functions was established with the R language. Then, the rock mass parameters were extracted from core mapping in the depth of 1500 m–2000 m and the BSD was presented in a similar manner to soil particle size distribution. Finally, the rock mass behavior under different block sizes was investigated. The results showed that Vb25 = 3.4 dm3, Vb50 = 6.4 dm3, and Vb75 = 11.2 dm3, which were the average percentages to represent the BSD. In the research area, therefore, the fractured rock mass was dominated by minor blocks. Besides, the variation of rock mass deformation vs BSD showed that the fractured rock mass was aggravated with the decrease in the block size. The results will enhance the effect of BSD on rock mass mechanical properties.
Highlights
In underground mining, the rock mass will undergo various types of behavior, which eventually leads to the destruction of the environment, such as plant destruction, surface subsidence, and groundwater pollution
The rock mass behavior is closely related to the rock mass integrity and mechanical properties
The empirical methods, i.e., the rock mass classification systems, are used to describe the rock mass integrity and behavior, which is dominated by block falls
Summary
The rock mass will undergo various types of behavior, which eventually leads to the destruction of the environment, such as plant destruction, surface subsidence, and groundwater pollution. The rock mass behavior is closely related to the rock mass integrity and mechanical properties. The empirical methods, i.e., the rock mass classification systems, are used to describe the rock mass integrity and behavior, which is dominated by block falls. The classification is divided into RQD, RMR, RMI, Q, and GSI (Ming and Peter, 2006; Rehman et al, 2018; Taherkhani and Doostmohammadi, 2015; and Zheng et al, 2018) These classifications have some limitations, not suitable in some cases, and may even cause severe consequences in underground activities (Kim et al, 2007; Stavropoulou, 2014). The natural fractures used to calculate the block size distribution (BSD) were mapped at a particular case in Yilgarn area, Western Australia. This research will enhance the awareness of the dependence of rock mass mechanical properties and its movement on the block size
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