1. School of Resources and Safety Engineering, Central South Univ., #932 Lushan South Rd., Changsha 410083, China; Visiting Scholar, Dept. of Mining and Materials Engineering, McGill Univ., 3450 University St., Montreal, QC, Canada H3A 0E8 (corresponding author).
2. Professor, School of Resources and Safety Engineering, Central South Univ., #932 Lushan South Rd., Changsha 410083, China.
3. Professor, Dept. of Mining and Materials Engineering, McGill Univ., 3450 University St., Montreal, QC, Canada H3A 0E8.