Sublevel stoping with applying artificial hardening stowing pillars for extraction of veins in complicated geotechnical conditions

In the process of underground mining of deep levels rock pressure can appear in any form, creating a serious threat to the lives of miners, disrupting the normal course of mining works and reducing the efficiency of mining production. The solution of the problem of rock pressure control becomes very urgent for underground mines developing vein deposits at a depth of more than 250 m. The aim of the study is the development and justification of mining methods to provide safe and efficient mining of deposits in complicated mining and mechanical conditions. In this paper, the factors of redistribution and dangerous concentration of stresses in the mined ore mass were identified, the methods of rock mass management in complicated geotechnical conditions were studied, and their advantages and disadvantages were revealed. It was determined that the sublevel stoping with the combined use of existing methods of rock pressure control and applying selfpropelled mining machinery is currently one of the most promising method finding widening application scope. In the context of Zarmitan gold ore zone the options of technological schemes of the sublevel stoping method were considered, providing for a combination of different methods of rock pressure control, allowing to minimize the disadvantages of one method through using the advantages of other ones. We proposed sublevel stoping options with artificial polygonal pillars and with artificial columnar pillars, which allowed to reduce ore losses in inter-stope pillars, arch pillars, and secondary dilution. In addition, artificial pillars, taking compressive/tensile stresses, prevent their concentration and create safe conditions for extraction at adjacent and underlying levels.

Rock pressure control methods based on detected regularities of stress formation in mining structures

Relevance. Subsurface mining at the Gaysky ore mine is intensifying because of the growing need in raw material. It leads to rapid increase in the depth of mining and to problems connected with the stability of mining system constructive elements. The effi ciency of the Gaysky deposit underground development is largely determined by mining system constructive elements stability. Ore cave-in in the chambers of the fi rst and second stages causes the growth of load in the interchamber pillars leading to their collapse, loss of boreholes and development headings. Mining productivity in the chambers of the fi rst, second, etc. stages falls, oversize yield grows, which also impairs the effectiveness of mining. Hanging wall and footwall cave-in in the deposit under consideration may be explained not only by host rock poor stability, but also by the presence of high compressive tectonic stresses, that were determined by the authors. Stress measurements in the rock mass have shown that the east-west stresses have doubled the northsouth stresses and have been 1.5 times as high as the vertical ones. The purpose of the research is to reduce stresses in stopes ore in place when excavating steeply dipping ore bodies using a sublevel stoping method with a hardening backfi ll. Research methodology includes full-scale experimental measurements of the stress state of the rock mass and ore in place at accessible depths and horizons of the deposit. A comprehensive scientifi c research method was used, including the analysis and theoretical generalization of stress distribution regularities in the arrays of the extracted chamber reserves and mathematical modeling of the behavior of the research object; theoretical results were compared with the results of instrumental observations. The analysis of the research results made it possible to establish the stress-strained state behavior in the course of mining. It was revealed that when mining a deposit using sublevel stoping, the most loaded elements are the hanging wall and footwall exposed parts, ceiling, interchamber pillars and bottom. Therefore, it is necessary to take measures to increase ore in place stability in order to guarantee the safety and effi ciency of the mineral extraction technology. Conclusions. Relieve slots method is among the most effective and frequently used active method of rock mass pressure control. The method has come into common use because it is easy to apply. Main labor inputs of a relieve slot creation are only reduced to extra drilling and blasting which do not require additional tunnel driving. The aim of the relieve slot is to create additional free surfaces for deformation, to redistribute rock mass stress-strain state, and remove stress from the protected element of the mining system.

Clustering-based iterative approach to stope layout optimization for sublevel stoping

SYNOPSIS Underground mining operations tend to have higher operating costs than surface mines. When metal prices decrease, profitability is jeopardized due to the high costs. Therefore, mining management harnesses new practices that increase operational efficiency. One way to manage this challenge is to invest in new mine planning practices. Stope layout optimization as a part of underground mine planning aims to identify a portion of the orebody in the form of production volumes (stopes) to maximize profit under roadway and stope dimension constraints. In this paper we propose a novel approach based on identifying ore-rich areas of the deposit and prioritizing their extraction through an iterative heuristic clustering approach. The proposed approach is compared with and validated by an exact method through a small mining example. The heuristics produced nearly identical results in a very short time. Finally, a case study was carried out using a larger data-set. The cluster-based iterative approach generated near-optimal stope layouts in a computationally effective manner. Keywords: underground mining, iterative optimization, stope layout planning, sublevel stoping.

Optimal Extraction Methods Selection for Kakosa South Copper Ore Deposit Applying Modified Technique for Order of Preference by Similarity to Idea Solution Model

Kakosa South copper deposit is located about 450km northwest of Lusaka between Chingola and Chililabombwe. A comprehensive study of Kakosa South deposit was carried out. In Kakosa area the footwall aquifer rocks comprising sandstone and conglomerates which are thin and as such are not expected to represent major aquifers. Copper mineralisation is found in the upper quartzite and ore-shale. The inclination of the deposit ranges from 250 up to 350 . The hangingwall formations above the upper quartzite are represented by a sequence of dolomite and shale formations. Based on Kakosa geotechnical analysis and rock mass classification, fuzzy TOPSIS approach was employed for the selection of optimal extraction techniques. FTOPSIS approach has precise and specific quantities which are used in order to establish criteria and option weights. Triangular fuzzy numbers were determined to represent semantic variables. The fuzzy numbers for Kakosa South parameters were used as input data in the decision making model and matched against the criteria required for the mining method. Applying FDM model, extraction techniques were ranked. The results indicated that open pit extraction technique was ranked first with 78.90 scores followed by sublevel stoping with 66.88 scores. It is concluded that the Kakosa South copper ore deposit can optimally be extracted by open pit mining up to transition depth and transit from open pit mining to underground mining employing sublevel stoping.