A New Combined Mining Method: The Stope Limit Length Calculation of Considering Bulk Support Boundary

• Published in: Rock mechanics and rock engineering 2024-09, Vol.57 (9), p.6909-6925
• Main Authors: Chen, Qingfa, Gan, Quan, Wang, Hui, Liu, Chenyang
• Format: Article
• Language: English
• Subjects: Area; Civil Engineering; Continuity (mathematics); Crown pillars; Earth and Environmental Science; Earth Sciences; Exposure; Geophysics/Geodesy; Hanging walls; Hydraulic mining; Hydraulic radius; Hydraulics; Manganese; Mining; Original Paper; Rock; Rock mass rating; Rocks; Stability analysis; Sublevel caving
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-024-03865-y

To tackle the technical challenges of medium-depth mining in sharply inclined medium-thickness ore bodies, the concept of an induced caving crown pillar was introduced, which led to the development of temporary crown pillar-induced caving technology. Building upon this foundation, a combined mining method of crown-pillar induced caving and non-pillar sublevel caving has been developed through integrating and restructuring mining techniques. Determining the stope limit length is one of the important elements to ensure the successful implementation of the combined mining method. The 37th stope of Daxin Manganese Mine is taken as the engineering background, and the Mining Rock Mass Rating is utilized to assess the stability of the stope rock mass. This assessment, combined with stability analysis and diagrams, aids in determining the zones of stable hydraulic radius and initial caving hydraulic radius. Formulas for calculating the hydraulic radius of the hanging wall rock, ore crown, and footwall rock are derived from the analysis of the exposed form of the first and continuous mining stopes. Taking into account the presence of bulk boundary support conditions in the continuous mining stope, the hydraulic radius weakening coefficient is determined by the ratio of the bulk support force to the horizontal original rock stress. The weakened-hydraulic radius is utilized in calculating the limit length of the continuous mining stope. When combined with the existing stope structure parameters, the solution for the limit exposure length of the combined mining method for the first and continuous mining stopes is 47m and 38m, respectively. By integrating specific engineering projects, the research results offer insights and a scientific basis for the technological transformation of mid-depth mining in sharply inclined medium-thick ore bodies. Highlights A combined mining method of crown-pillar induced caving and non-pillar sublevel caving was developed. The hydraulic radius values of the rock mass in the mining area are obtained through MRMR. According to the definition of hydraulic radius, the ultimate exposed length of the mining area can be inversely deduced. A method for calculating the weakening coefficient of MRMR evaluation is proposed when bulk support boundaries exist.