# An Experimental Study of Industrial Site and Shaft Pillar Mining at Jinggezhuang Coal Mine
## 1 Introduction and Geological Conditions  
### Introduction  
Shaft pillar mining is typically carried out before closing a coal mine. The coal resources available for mining have decreased owing to economic development and an increase in coal mine production. Hence, mines are experiencing the problem of coal resource exhaustion. Numerous collieries excavate shaft pillars to maximize profits before they are closed. There are two main components of shaft pillar mining, i.e., the rock movement theory and technologies for the protection of shafts and facilities. The relationship between shaft and pillar positions has been investigated since the 1960s. Most of the research in this field has focused on technologies such as symmetric extraction, harmonic extraction, and partial caving [1]. In the Akabira Colliery, the shaft was damaged after 2.2 million tons of coal was excavated from the original shaft pillar [2]. Pillar safety is generally evaluated using numerical models. [PERSON] designed a shaft pillar and stop area and evaluated shaft stability using FEM (Finite Elements Method) simulation [3]. In Poland and Germany, the Knothe theory and [PERSON]'s theory were primarily used to calculate shaft subsidence and deformation [4, 5]. Numerical simulation models, such as FIAC\({}^{\text{3D}}\) and FEM, were used to calculate the influence of shaft pillar excavation [6, 7, 8]. The researchon pillar failure shows that remnant pillars typically have a dynamic failure process and brittle shear zones [9; 10]. In recent years, surface mining subsidence monitoring technology has developed rapidly. Differential interferometric synthetic aperture radar (DInSAR) technology can obtain surface deformation with pairs of SAR images and has been used widely in mining subsidence monitoring [11; 12; 13]. The surface deformation and settlement caused by mining can also be obtained using multi-period lidar point cloud registration calculation difference [14]. Those technologies are used widely and played positive roles in the practice. Furthermore, the sensors, such as FBG and strain sensors used in the shaft well deformation monitor [15], provide detailed internal monitoring information. Underground measures are used in most collieries [16], such as partly excavating or using the backfill mining method. A shaft is generally built on a simple geological area and it can be mined at a low cost. Several shaft pillars have been mined successfully, such as the Xinglongzhuang colliery in Yanzhou, Datong colliery in Huainan, and Dahuangshan colliery in Xuzhou. However, there is no technology that can be generalized using in shaft pillar mining. In situ measurement-based methods are important for preventing damage to shafts [17]. Shaft pillars are generally built under industrial construction sites such as shafts, hoist houses, coal wash plants, and office buildings. These buildings should be protected when underground pillars are mined out. A shaft is a strategic passage for an underground coal mine. Thus, a shaft pillar is typically mined immediately before a colliery is closed and it should be investigated for safety before being mined. A large amount of coal mine resources have been exhausted owing to economic development and large energy consumption. This study has developed a method based on experiments to excavate resources in complicated surface and underground conditions. The proposed method is based on actual geological conditions and prioritizes safety. It provides an example for industrial square and shaft pillar mining. Fulfilling the aims of this study was expected to find a balance between coal resource mining and building protection and try to improve the recovery rate while reducing the loss of shaft and building. A new pillar was designed for the shaft based on the surface monitored data. It can reduce the coal pillar under the shaft and extend the production life of the mine as much as possible. In particular, this paper contains two parts research contents.