Key engineering science and technology strategy for green, intelligent and sustainable development of deep metal mines in China

(1) Precision cutting mining

The traditional method of rock breaking in mining is drilling and blasting. Drilling and blasting technology will damage the stability of surrounding rock and threaten the safety of mining. Moreover, this method will mine ore and waste rock together, which greatly increases the amount of waste rock and the workload of beneficiation operations. In order to improve the level of automatic, accurate and efficient mining in deep Wells, the method of precision cutting mining must be studied.

1. Mechanical continuous cutting and mining technology

The method of mechanical excavation and mechanical drilling is adopted to replace the traditional blasting mining technology with continuous cutting equipment, and the cutting space significantly improves the stability of surrounding rock because blasting is not required. Mechanical cutting can accurately mine the target ore, implement precision mining, and minimize the mining loss rate and ore dilution rate, thus greatly reducing the workload and the amount of beneficiation work. The process of cutting, loading and transportation is carried out in parallel, which creates conditions for realizing continuous mining, improving mining efficiency and ensuring mining safety. Mining machine operation is limited by the variable and complex geological conditions of metal deposits and the life and cost of cutting heads, which are two key frontier issues to be solved in the implementation of this technology.

2. High pressure water jet rock breaking and mining technology

High pressure water jet technology is a new cleaning and cutting technology developed in the 1970s. The high-speed water jet emitted from the high-pressure nozzle has great energy, can produce a huge impact force on the target, and can be used to cut rocks, break rocks, etc. High-pressure water jet crushing and cutting process, can automatically discharge the waste, only after the use of water for simple physical purification, can realize the recycling of water. At present, high pressure water jet rock breaking has been realized in soft rock and medium hard rock engineering, and has been widely used in coal mines. However, there are still some problems such as insufficient water jet pressure when breaking hard ore rock, so its application in metal mines is limited. In order to solve the problem of hard rock breaking, the high pressure water jet needs to be developed in the direction of ultra-high pressure and high power. Therefore, it is necessary to further develop and improve ultra-high pressure water jet components and equipment, such as ultra-high pressure pumps, rotary seals, wear-resistant nozzles and high-pressure pipe fittings and other components, to create favorable conditions for their application in metal ore hard rock.

3. Laser rock breaking and mining technology

Laser rock breaking is the use of high energy laser beam generated by the heat of the local rapid heating of the rock, when the temperature is high enough, there will be a series of complex physical and chemical reactions, and with the temperature rise in turn to achieve three rock breaking forms of crushing, melting and vaporization. Mining rock can be broken as long as it is broken. When the high energy laser acts on the rock surface, the local rock is rapidly heated and expanded, resulting in an increase in local thermal stress. When the thermal stress is higher than the ultimate strength of the rock, the rock will be thermal broken to achieve cutting and breaking. In addition, micro-cracks and pores on the rock surface reduce its ultimate strength, which will aggravate this thermal crushing and cutting effect.

4. Plasma rock breaking and mining technology

When using plasma rock breaking, it is necessary to drill a hole into the rock mass first, then install the coaxial blasting electrode tightly into the hole, and fill the front of the hole with electrolyte. By detonating the trigger, the energy storage capacitor bank connected with the coaxial blasting electrode is connected. Under the action of high electric energy, the electrolyte is quickly transformed into high temperature and high pressure plasma gas. The high temperature, high pressure plasma gas rapidly expands to form a powerful shock wave, resulting in a blasting effect similar to that produced by chemical explosives, and the pressure generated can exceed 2 GPa, which is high enough to crack hard rock. The implementation of this technology can greatly improve the working environment and reduce the impact and damage of traditional blasting on surrounding rock and environment.

(2) No waste mining

The goal of waste free mining is to minimize the output and discharge of waste, improve the comprehensive utilization rate of resources, and reduce or eliminate the ecological and environmental damage caused by mineral resource development. The waste free mining mode follows the point of view of industrial ecology, takes mining activities as the center, links the mine ecological environment, resource environment and economic environment to form an organic industrial system, and obtains the maximum amount of resources and economic benefits with the smallest emission. After the end of mining activities, the mine environment and ecological environment are integrated through the minimum end treatment. In order to realize waste free mining, it is necessary to improve the level of mining technology, reduce the ore dilution rate, minimize the waste output, and control the waste rock yield from the source. At the same time, as far as possible to improve the recovery rate of beneficiation, reduce the discharge of tailings, the ore resources due to the low level of smelting and can not be used to minimize the composition. In addition, strengthen comprehensive recycling, realize the recycling of waste, improve the overall utilization level of waste, and strive to achieve zero discharge and zero storage of mine solid waste.