## 2 Brief Introduction of Shrinkage Method  
The shrinkage method is characterized by the following: the stage is divided into ore blocks, which are divided into rooms and pillars. The ore room recovers ore in layers from the bottom up; each time the collapse of the ore releases about \(1/3\), and the rest of the storage in the ore room is a working platform to continue to mine upward. After the entire mine is mined, all of the remaining ore will be released, as shown in Figure 1.  
The shrinkage method has the advantages of a simple structure, convenient management, small development engineering, easy to master process, and easy to acquire the required equipment, but its disadvantages are also particularly obvious, mainly including the high dilution rate of recovery losses. The loss rate of ore and the dilution rate of ore are the two most important indicators for mining enterprises in production management. The dilution rate refers to the ratio of the difference between the industrial grade of the ore and the grade of the mined ore in the  
Figure 1: Diagram of the shrinkage mining method. stope to the industrial grade of the ore, and the ore loss rate is the ratio of the difference between the metal content of the ore in the mine and the metal content of the ore mined to the metal content of the ore in the mine. The comprehensive recovery rate is also a commonly used indicator, and the sum of the comprehensive recovery rate and the ore loss rate is 100%. Higher dilution and loss of ore is a problem that causes waste of mineral resources and adversely affects the economic benefit of mining enterprises. In the process of mining, the reserved pillars are usually not mined, and only in the case of high value of the pillars will they consider using concrete pillars for replacement, but the construction of such concrete pillars is extremely complex and inefficient. At the same time, if the mining area is high in sulfide or clay-like minerals, the crushed ore may bond in the mining area, which may also cause problems in centralized ore release, leading to a loss of ore volume. [PERSON]'s statistics on the ore loss rate of various mining methods in mines around the world show that the average loss rate is 14.9% for the shrinkage method and 5.3% for the fill method [50]. High labor intensity and low operating efficiency of manual production  
[PERSON], [PERSON] [1] argues that the shrinkage method is considered to be a mining method used in the days when mechanization was rare. Due to the limitation of space in the mining operation of the shrinkage method, mechanized equipment is difficult to be applied, which is why many countries have converted the shrinkage method to other mining methods [2]. The shrinkage method uses pneumatic rock drills in the mining area and electric rakes to discharge the ore (see Figure 3), whereas other mining methods, which can be better utilized, use drill jumbos to drill the rock and LHDs to discharge the ore. [PERSON], [PERSON], et al. [2] suggested that the productivity of the shrinkage method is also related to the proficiency of the workers in cooperation with the geo-engineers, and that the labor-intensive mining method of the shrinkage method does not allow it to be widely used in modern mines. Tailings disposal difficulties  
In the process of ore recovery, due to the low content of useful components in the ore, after beneficiation [28], it often produces a large amount of tailings. And when the mine uses the shrinkage method, tailings are not disposed of by filling the mining area and are often disposed of in a tailings pond. Studies have shown that improper handling of tailing ponds can cause many problems. During the dry season, the tailings particles are small and can easily drift into the surrounding area, polluting the air and soil and even jeopardizing people's health. Similarly, heavy metals and residual agents in the tailings can cause water, air, and soil pollution, and even endanger human health [52; 53; 54].