Deep mine cooling,a case for Northern Ontario:Part Ⅰ

Cooling energy needs, for mines in Northern Ontario, are mainly driven by the mining depth and its operation. Part I of this research focusses on the thermal energy loads in deep mines as a result of the virgin rock temperature, mining operations and climatic conditions. A breakdown of the various heat sources is outlined, for an underground mine producing 3500 tonnes per day of broken rock, taking into consideration the latent and sensible portions of that heat to properly assess the wet bulb global temperature. The resulting thermal loads indicate that cooling efforts would be needed both at surface and underground to maintain the temperature underground within the legal threshold. In winter the air might also have to be heated at surface and cooled underground, to ensure that icing does not occur in the inlet ventilation shaft-the main reason why coolin~ cannot be focussed solely at surface.

Deep mine cooling, a case for Northern Ontario:Part Ⅱ

Cooling energy needs, for mines in Northern Ontario, are mainly driven by the mining cooling technologies available and the cost to implement them in a 2500 m deep underground mine. The cooling technologies reviewed herein include mechanical and natural cooling systems, ranging from mechanical chillers to seasonal thermal storages. The economic and operating parameters for each technology were estimated and evaluated according to the mine's energy loads. Including consideration of any combined heat and power benefits of the technology, cooling tower requirements, etc., the resulting cost of implementation for each technology could be ranked. This showed that the natural thermal storage systems and conventional chillers were the most cost-effective, mainly since the natural systems had very low operating cost and the chillers had relatively low capital costs.

Rock creep modeling based on discontinuous deformation analysis

Creep is one of the major problems of deep underground mining that must be studied theoretically,experimentally,and numerically over a long period.Experiments and feld tests are methods which can directly and more accurately describe the engineering practices as compared with others.However,these approaches are also time-consuming because creep problem of rock engineering,such as the roadway/tunnel squeezing phenomenon,usually lasts from several months to a few years.A numerical method can be employed to overcome this time-consuming problem.The discontinuous deformation analysis(DDA)method was originated in 1984 and received considerable attention from geo-engineers and researchers.The current paper discusses the creep calculation methods using the continuous and the discontinuous methods,and proposes a creep analysis method based on DDA.The method proposed in this paper can directly change the stiffness matrix while inheriting the advantages of the original DDA.Applying this method does not require any changes in the contact part of DDA.Thus,this method does not have any effect on the open–close iteration and convergence and can solve the creep problem,while maintaining the advantages of the original DDA.We theorized that creep problems are static problems,and based on this,the work using DDA in this study was divided into two parts:(1)addition of a new loop for the original DDA to‘‘discredited’’the total creep time into several time elements,thereby changing the material properties in each time element;and(2)division of each of the time elements by the time steps,similar to the original DDA.In this manner,one creep problem can be solved via assembling of static problems.Afterwards,the method mentioned above is employed to modeling a tunnel case.The evolution of the displacement fled and stress feld during creep are analyzed and discussed.

Guidance and review:Advancing mining technology for enhanced production and supply of strategic minerals in China

Mineral resources,often referred to as“industrial food,”play a pivotal role in the national economic construction sector.Specifically,strategic minerals(SMs)bear a direct influence on the development of emerging strategic industries within China.This paper aims to shed light on the supply and demand dynamics,current status,and characteristics of SMs from the perspective of China's national security.We offer a comprehensive review of the current status and challenges associated with SM mining technology in China.Our analysis spans various mining methods,including open-pit mining,deep underground mining,green mining of complex underground bodies,integrated underground mining and processing,and intelligent mining.Within this framework,we delve into multiple initiatives aimed at improving the status of the mining industry,increasing production,and maintaining the adequate supply of these resources.We discuss these strategies from both a top-level policy and system design perspective,as well as detailed implementation plans.