Shandong some gold ore mine built in 1975, using mining method while mining exploration to shallow hole Shrinkage Method based, residual mined-out area and a large portion of the poor are not recoverable ore. In recent years, some shallow old goafs have been filled at the same time without filling multiple middle sections, mainly returning the top, bottom, inter-column and residual ore bodies remaining in the old goaf. Repeated mining of shallow ore bodies destroys the equilibrium state of the stress field in the old goaf, causing the activation of the old airspace and inducing a sudden collapse of the mountain, which seriously threatens the mining production plant and the shallow lifting shaft. To this end, this study verified the mine's old goaf and analyzed the effects of full activation and deep mining on the vertical deformation of the old goaf. 3.2 Analysis of the impact of mining on the shaft In order to calculate the impact of mining above the level of -60m on the shaft, it is necessary to calculate the sinking and horizontal movement values ​​at the wellhead. To simplify the calculation, this study equivalents mining above -60m to a mining area. According to surface movement observation data, stratum lithology and mining method, the predicted parameters of mining subsidence above -60m level selected in this study are: sinking coefficient 0.3, horizontal movement coefficient 0.28, main influence tangent 1.8, mining influence The propagation angle is 90°-0.75α (α is the inclination angle of the ore layer, 45° in this study), the equivalent thickness of the ore body is 15m, the projection length of the equivalent tendency level is 80m, the ore body orientation reaches full mining, and the mining depth reaches 100m. The mining depth is 160m and the shaft depth is 200m. In the probability integral method [3], the wellhead coordinate y=100m is calculated in the coordinate system. The maximum surface subsidence is 3182mm, the maximum horizontal movement value is 891mm, and the main influence radius is 88.9, 55.6m. At the wellhead (y=m), the surface subsidence and horizontal movement values ​​predicted by the probability integral method are 575,192 mm, respectively. The analysis shows that the upper part of the shaft will move toward the downhill direction of the ore body, causing the shaft to be inclined down the mountain. The average inclination of the shaft is 0.96mm/m, and the deformation of the shaft wall caused by the sinking of the shaft well is 2.9mm/m. The degree of deformation and failure of the shaft is related to the lithology, thickness, dip angle, structure, hydrological conditions, shaft structure and construction quality, equipment in the shaft and resistance to deformation, and mining methods of the shaft passing through the formation [4]. Therefore, the tensile (compression) amount of 2.0 mm/m and the inclination of 2.0 mm/m are generally taken as the ultimate deformation values ​​of the reinforced concrete pouring wellbore. The research shows that: 1 When the old goaf above -60m level is fully activated, the shaft inclination value reaches 50% of the limit value, which has certain influence on the shaft lifting; 2 horizontal compression deformation is close to the limit value, and some well wall will be broken. It will have a more significant impact on the shaft.
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1 Overview of the mining area The exposed strata in the mining area are mainly the Quaternary of the Cenozoic and the Lower Proterozoic - Archean Group of the Jiaodong Group. The Quaternary strata of the Cenozoic are mainly distributed in the southeast, southwest and northwest of the mining area, and are composed of sub-clay, sand and gravel of the alluvial and alluvium. Mine I# alteration zone is stable, tending to NW, and the inclination angle is about 45°. Altered rock predominantly less yellow phyllic, phyllic, yellow phyllic granite silicide, granite, general alteration width of 5 ~ 15m. The shallow old goaf is mainly located at 0-60m level. There are different degrees of cracks in the shaft, wellhead room and shaft wall of the shallow mining affected area. The mountain has a large collapse pit, and the collapse pit and the old goaf. The area is connected, large cracks appear on the surface, and the wall is destroyed (Fig. 1, Fig. 2).
2 Detection of the occurrence of old goaf and its activation
2.1 Detection of the occurrence of old goaf 
2.1.1 Geophysical Exploration and Drilling Verification The SYT method of geophysical exploration was carried out in the shallow mining area, and 150 object detection points were arranged. According to the results of geophysical exploration, the drilling engineering was arranged to verify the occurrence of the old goaf, and a total of more A number of old goafs were found in the drill holes, as shown in Table 1.
2.1.2 Three-dimensional laser scanning detection and verification Compared with the traditional measurement methods, the three-dimensional laser scanning technology does not need a cooperation target, and can automatically, continuously and quickly collect data, and directly acquire the spatial three-dimensional coordinates of each sampling point on the surface of the object in a non-contact manner. Obtain a set of points representing the entity, which can be applied to detect the geometry and volume of the old goaf [1]. In this study, the old mined area of ​​the mine was detected by the C-ALS cave 3D laser scanner of the British MDL company. The EW strike, the inclination angle of 44°, the east-west length of 22.24m, and the north-south length of 10. 24m, old goaf with a depth of 12.418~29.682m and a volume of 458.40m3.
2.2 The activation of the old goaf shows that the surface movement and deformation is the result of the underground mining space spreading to the ground. When the surface of the old goaf is again sunken, the building is inclined and cracks, it means that the old goaf occurs. Activated and has appeared to the ground. The surface movement deformation process is affected by various geological mining factors and is a very complicated space-time mechanical process. At present, only through field observations, based on the analysis of observational results to study the law of surface movement, to provide a scientific basis for solving mining damage problems [2]. In order to monitor the activation of the old goaf in the mine, a surface movement observation station was set up in the shallow mining area. The surface movement was monitored regularly by GPS, total station and level. The surface subsidence basin was monitored to be 450m long from east to west. The direction is 600m long, and the cumulative maximum sinking amount of 5a is 460mm. The sinking curve of the north-south direction of the mining area is shown in Figure 3. The volume of the subsidence basin is about 33,000 m3. According to the lithology and mining method of the stratum, the volumetric propagation coefficient of the mining space is 0.3, and it is estimated that about 110,000 m3 of the old goaf has been activated in the past 5 years.
A variety of technical investigations show that there are a large number of old empty areas in the shallow part of the mining area, and the residual mining is the driving force for the activation of the old goaf. The activation of the old empty area is the root cause of the mountain collapse, surface movement and shaft deformation.
Influence of mining above 3-60m level on shaft deformation
3.1 Overview of the shaft The mine shaft was built in 1983. It is the main lifting well in the shallow part of the mining area. The shaft wall is reinforced concrete and is constructed in sections. The shaft diameter is 3m and the depth is 200m. The ground and the wall are different. The degree of cracks. The relative positional relationship between the shaft and the ore body is shown in Figure 4.
3.3 Development trend of shaft deformation It is expected from Figure 4 that the horizontal ore body of -60～-125m is still located within the scope of the shaft protection pillar, and the filling method is used below the level of -60m, the sinking coefficient will be significantly smaller, so sinking The coefficient is taken as 0.1. According to the specific mining conditions, the surface subsidence and horizontal movement at the wellhead are less than 10mm, that is, the -60~-125m horizontal ore body mining has no effect on the shaft, but the deep mining will destroy the stress balance of the old goaf. As a result, the old goaf continues to be activated, which has an impact on the shaft. According to the prediction of shaft deformation above -60m level, the full activation of the old goaf will have a significant impact on the shaft. Therefore, it is necessary to fill the old goaf and dynamically monitor the deformation of the shaft.
4 Conclusion Taking a gold mine in Shandong as an example, geophysical prospecting, drilling and cave laser scanning methods were used to detect the occurrence of the old goaf, and the activation of the old goaf was carried out by probability integration method. The quantitative analysis of the influence of deep mining on shaft deformation has certain reference value for efficient treatment of the old mining goaf.
References [1] Zeng Kai, Jiang Yan. Application of 3D laser scanning technology in surface subsidence monitoring [J]. Earth and Mineral Surveying and Mapping, 2015, 31(2): 28-30.
[2] Jiang Yan, Xu Yongmei, PRUESSEA, et al. Prediction theory and application of surface movement deformation [M]. Xuzhou: China University of Mining and Technology Press, 2015.
[3] Deng Kazhong, Tan Zhixiang, Jiang Yan, et al. Deformation monitoring and subsidence engineering [M]. Xuzhou: China University of Mining and Technology Press, 2014.
[4] Ni Xinghua, Yan Wanghua, Guan Yunzhang, et al. Coal Mine Shaft Wall Fracturing Prevention Technology [M]. Xuzhou: China University of Mining and Technology Press, 2005.
Article source: "Modern Mining", 2017.3
Author: Jiang Yue; School of Earth Science and Engineering, Shandong University of Science and Technology Wang Hui; Shandong Gold Mining Company Limited;
Xu Letian; School of Electronic Communication and Physics, Shandong University of Science and Technology;
Jiang Yan;Shandong University of Science and Technology, School of Surveying and Mapping Science and Engineering Copyright:
