Mining industry in Mozambique

At present time,Mozambiqueis called the “Rising Star of South Africa” mainly due to the rapid development of its mining industry. Mineral resources sector ofMozambiqueis one of the most dynamically developing sectors of the country’s economy.China,BrazilandIndiahave recently become the main partners forMozambique. Recently, a number of projects is being implemented in the country, for example, Auroch Minerals Manica Gold in gold production. Increasing coal production is connected with commissioning of the Moatize open pit, which is being developed by Brazilian Vale Company, as well as Benga mining company owned by Indian ICVL consortium. The analysis of the extraction of certain mineral types inMozambiquepresented in the paper demonstrates general picture of mining industry development in the country. The analysis findings allow identifying the causes of negative phenomena in the industry, manifesting themselves in decreasing production of certain types of minerals. For instance, the main reasons for the decline in coal production were dropping labor productivity, deterioration of mining conditions, and depletion of the most accessible coal reserves, extractable by open pit mining. In this regard, development of underground mining methods providing for opening of deep deposits by vertical shaft sets is highly relevant. The experience of the neighboringRepublicofSouth Africashows that, in the mining and geological conditions of the south of the African continent, highspeed shaft sinking methods accelerating deposit development can be successfully applied.

Simulation Analysis and Experimental Study on the Working State of Sinking Headframe in the Large Underground Shaft

Based on the newly developed sinking headframe for the deep and large shaft, the finite element model of the full-scale headframe was established by using SAP2000. Through the calculation, the theoretical stress of the headframe at sinking depths of 40 m, 143 m, 223 m, 518 m, 762 m, 1000 m, 1250 m, and 1503 m was obtained and then compared with the field measured stress. The results show that with the increase of shaft sinking depth, the theoretical stress of finite element simulation and the field measured stress of each member of the sheave wheel platform and the headframe increase linearly, and for the maximum member stress in the upper, middle, and lower layers of the headframe, the numerical simulation value is greater than the field measured value and less than the designed steel strength. In other words, under normal working conditions, headframe members are in the elastic stress stage and meet the design requirements, and instability failure of headframe members will not occur. The end-restraint mode of the supporting bars has a great influence on the force of the top member. The reasonable selection of the restraint mode in the simulation is the key to the accuracy of the calculation results. The simulation results well reflect the actual stress of the headframe and provide a reliable guarantee for the follow-up work of the project.

Influence of Hydrogeological Investigation’s Accuracy on Technology of Shaft Sinking and Design of Shaft Lining—Case Study from Southern Poland

Accuracy of hydrogeological and geotechnical investigation in place of shaft sinking is a key factor for selection of sinking method and design of the shaft lining. The following work presents the influence of the rising level of accuracy of geological data gathered in the area of shaft sinking in the Silesian Coal Basin and technical projects of shaft lining and technology of its sinking, which have been changing over the years. The initial project of the shaft was repeatedly modified. Each modification eventuated in rising requirements for the shaft lining, such as increasing its thickness or changing concrete class. It has become necessary to use additional methods of reinforcing rock mass around the shaft.

Optimization Directions for Monitoring of Ground Freezing Process for Grzegorz Shaft Sinking

Grzegorz shaft is the first mine shaft sunk in 21st century in Silesian Coal Basin in USA of ground freezing method. Work carried out by Shaft Sinking Company (PBSz S.A.) is characterized by high level of innovativeness. Geophysical measurements were conducted to find directions of optimization of ground freezing process and its monitoring. Data gathered during research is a starting point for finding directions of optimization of particular fields during Grzegorz shaft sinking, as well as to be used in future similar ventures. Proposed solutions might have bring real improvements for safety and effectiveness of work and also for economic factors. Conducted tests and analysis aim at improvement of monitoring of shape, size and quality of frozen rock mass column in a safe and reliable manner.

Prospects of Shotcrete Shaft Lining for Underground Sustainable Mining

Investment in underground mining is coming down all over the world, but deep reserves are available for extraction. Conventional sinking and lining of mine shaft projets or pits for winding men and materials from deep underground mines are getting very costly and being deferred. We found Polish technology of Shaft sinking with monolithic mining very efficient in Sudamdih, Monidih and Satgram projects in India. Russian collaboration for Jhanjra for shaft sinking and mine construction for large mine has been successful. Underground production is declining world over, while remaining reserves are at greater depths. Designing and coding original model programs by collecting actual field data to run the programs to determine cost benefit at different depths with standard diameters has been done. Most companies are avoiding deep mining projects, because of exorbitant cost of shaft sinking. As per experience of the researcher, pre-split blasting and shotcrete lining can be much faster and cheaper. So model programs have been designed and run with practical field cost and technical data, as exemplified in this paper. Future of deep pit mining will be assured with successful adoption of the method in projects, especially through hard rock strata

Numerical simulation of vertical shaft sinking using artificial ground freezing

Artificial ground freezing (AGF) is used worldwide for vertical shaft sinking in difficult hydrogeological conditions. The modern tendency is to determine the design parameters of the freezing technique based on numerical simulation. This work is devoted to the numerical simulation of the formation of an ice-soil wall in the soil stratum due to the AGF and shaft sinking under the protection of the wall. For this purpose, a fully coupled thermo-hydro-mechanical model of soil freezing has been developed on the basis of the theory of poromechanics. The developed model considers important features of the freezing process, such as the phase change, pore water migration due to cryogenic suction, frost heave, and consolidation of the soil. The results have shown that the model allows to predict the distribution of ice content, assess stress and strain in the ice-soil wall, and estimate displacement of the excavation wall.

Rapid Mechanized Shaft Sinking

REDPATH DEILMANN GmbH from Germany has been sinking and lining two shafts and initial underground development since 2017 on the territory of the Republic of Belarus (Starobinskoe potassium salt deposit, Luban) by request of Slavkaliy LLC. Shaft sinking is one of the most complicated and time-consuming stages in renovation and construction of new underground mines. In the absolute majority of cases, shaft sinking and lining are at the critical path for implementation of such projects. Rapid rates of shaft construction ensure high technical and economic performance during the commissioning phase and earlier supply of end products to the market. The article introduces an innovative method of mechanized mine shaft sinking that provides rapid parallel sinking and lining of the mine shafts. Unique mechanized shaft boring roadheaders (SBR) manufactured by Herrenknecht are employed. Shaft sinking is done in complicate geotechnical and geological conditions intensified by a very low stability of the rocks using a dedicated rock freezing method. Modern materials are used for additional hydrosealing of the tubing liner. Workings in the near shaft insets are driven with roadheaders. A combination of all these solutions makes it possible to accelerate shaft sinking in a safe way without blasting operations and with high technical and economic performance both for the shaft sinking project and the overall construction of the mining and processing plant.