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

I. Introduction

Mineral resources are the first industrial raw materials in the world, and play a pivotal role in the development of national economy and social material civilization and scientific and technological progress. After years of continuous high-intensity development, the shallow metal mineral resources in China are gradually reduced or exhausted, and the mining of metal mineral resources is in the stage of all-oriented deep propulsion. At present, more than 20 underground metal mines have reached a mining depth of 1000 m or more. According to statistics, in the next decade, more than one-third of China's underground metal mines will have a mining depth of more than 1000 m, of which the maximum mining depth will reach 2000~3000 m. With the progress of exploration technology and equipment, it is entirely possible to find a number of large metal deposits in the depth of 3000-5000 m in our country in the future. Therefore, deep mining is the most urgent problem facing the development of metal mineral resources in our country, and also the most important way to ensure the sustainable development and supply of metal mineral resources in our country in the future. In this context, we put forward the key engineering strategies to solve the deep mining problems from a forward-looking perspective.

Second, the key problems facing deep mining

Safe and efficient deep mining is faced with a series of engineering challenges, and the key problems are mainly from the following aspects:

① High ground stress. Under the action of high ground stress in deep depth, mining excavation will form destructive ground pressure activities, leading to the occurrence of mining power disasters such as rock burst, collapse, roof fall and water inrush, which seriously affect production safety and normal operation.

② Lithology deterioration. After entering deep, the rock mass structure and mechanical properties will change greatly, which brings great burden to support and subsequent mining safety, and seriously affects mining efficiency and benefit.

③ High temperature environment. The high temperature environment of deep mine will greatly degrade the mechanical properties of surrounding rock, seriously affect the safe operation of equipment, working efficiency and the health of workers, and cause unpredictable disasters and accidents.

④ Deep well lifting. With the increase of mining depth, the lifting height of ores and various materials increases significantly, resulting in a significant increase in the difficulty and cost of upgrading. Traditional rope hoisting technology is not only difficult to meet the requirements of deep hoisting, but also poses a potential threat to production safety.

Third, deep mining key engineering science and technology strategy

(1) Rock burst forecasting, prevention and control technology

Rock burst in metal mine is a kind of dynamic disaster caused by mining and is the main type of disaster in mining engineering. Rockburst prediction and prediction is a world-class problem. Understanding and controlling rock burst is the primary task of mine safety maintenance. Mining excavation destroys the stratum equilibrium state and generates disturbance energy in the surrounding rock. When the disturbance energy accumulated in the rock mass reaches a very high level, and the rock mass cracks or encounters faults due to high stress, the energy is suddenly released, and the rock burst may be formed. This is an accurate understanding of the rock burst mechanism. Based on rock burst mechanism, rock burst prediction should be closely combined with mining process. According to the future mining plan, numerical simulation and mathematical statistics are used to quantitatively calculate the size, time (mining time) and spatial distribution of disturbance energy induced by mining in rock mass in the future and its change law with mining process. Then, with the help of the knowledge of seismology (the relationship between earthquake energy and earthquake magnitude), the development trend and the "time-space-intensity" law of mining induced rockburst in the future can be theoretically predicted. Also based on the induced mechanism of rockburst, the prevention and control of rockburst should mainly start from optimizing the mining method, mining layout and mining sequence, reduce the high rock stress concentration and large displacement in the surrounding rock, reduce and control the accumulation of disturbance energy in the mining process, so as to reduce and control the occurrence of rockburst. At the same time, the support measures which can absorb energy and prevent impact are adopted to prevent and weaken the impact damage of rock burst.

(2) Support technology

The mining methods of underground metal mines, depending on the excavation and support methods, are divided into three categories: open-pit method, caving method and filling method, of which filling method has the highest cost. According to the difference of ore value and goaf maintenance difficulty, each mine decides its own mining method. However, in order to realize green mining, control rock movement and surface subsidence, especially control intense ground pressure activity after entering deep mining, filling method will be the mining method that most mines (including iron ore) have to choose. This is a major change from the traditional mining model. However, the principle of balancing mining value and support cost still needs to be observed. In order to widely use the filling method, it is necessary to carry out major reforms on the filling technology and filling materials, and greatly reduce the filling cost. The filling technology using mine solid waste is the most widely used technical scheme. The all-tailing paste filling technology developed in recent years can obtain high quality filling body under the condition of low cement consumption, uniform strength of paste, high topping rate of filling gob, and effective control of ground pressure activity and rock movement. This technology represents the future development direction of filling technology. In addition, the cementing material accounts for a large proportion of the paste filling cost. The study of ultrafine, high-strength, cheap and quick-setting filling materials can effectively reduce the filling cost.