## 3 Application of 5G+ Big Data in Fully-Mechanized Mining Face with a Super-Large Mining Height
### Roof Control in Fully-Mechanized Mining Face with a Super-Large Mining Height
Due to the excessive speed of the shearer, the amount of coal in the conveyor is too large, resulting in the overload of the conveyor. Therefore, during the weighting period of the working face, in order to prevent the roof from being supported in time due to the overload of the conveyor, it is necessary to monitor the working face through the three-dimensional digital twin system of the working face, and control the shearer with the automatic coal cutting system of the shearer. The speed of the shearer is controlled below 11 m/min, and it is best to control it at 10 m/min, which can not only control the roof but also keep up with the output. In view of the initial mining and strong caving stage of 12,403, it is difficult for the roof to collapse for the first time when 12,404 starts the mining stage of the working face. At this stage, the mining speed should not be too large to prevent the overhanging distance from being too large. Taking the three-dimensional digital twin system of the working face as the core guidance, through the three-machine automatic speed control system, the coal transportation volume of the conveyor is limited, and the position of the shearer is accurately positioned with the precise positioning technology of the shearer and the automatic coal cutting technology. The position of the shearer is accurately positioned, and the roof and floor are cut flat to ensure the support effect of the support and to ensure that the fully-mechanized mining face will not cut the roof and leak the roof. Then, with the help of the electro-hydraulic control and attitude monitoring system of the support equipped with HarmonyOS, the support is timely erected to support the roof and ensure that all the supports reach the initial support force of 25.2 MPa. When the fully-mechanized mining face is advanced to about 40 m from the main side of the open-off cut, the support reduction should be minimized when the support is moved. The support that can be moved under pressure or  
Stage II, the maximum current in Section B far exceeds the overcurrent threshold, reaching 464.28 A, with a long time of exceeding the overload current section. Therefore, the roof control is difficult. A comparison of the speeds of the coal machines in the same time period, as shown in Figure 15, shows that the maximum speed of the coal machines is 17 m/min. When the speed of the coal machines is lower than 12 m/min, the current of the conveyor is normal. Therefore, at this stage, when the roof condition is poor, the speed of coal machines should be strictly controlled, so that it is lower than 12 m/min. Strict control of roof safety is required. Centralized lubrication of the three machines and the sheared ensures the reliability of the equipment. By utilizing precise positioning technology for the shearer, the coal-cutting speed is strictly controlled. In the event of a roof collapse risk, all personnel assist in timely roof and side protection, reducing the amount of gangue entering the conveyor, while simultaneously decreasing the shearer speed and controlling the cargo volume to prevent conveyor overload. In the case of roof separation, the \"roof contacting and moving method\" is employed based on the electro-hydraulic control and attitude monitoring system of the system equipped with HarmonyOS. When the roof is broken or collapsed, the pre-support method should be adopted. When weighting occurs but the roof conditions are stable, it is essential to strengthen the support and advance quickly to alleviate the pressure, as shown in Figure 16.  
Figure 14: Diagram of current variation of conveyor when the buried depth of fully-mechanized mining face is more than 200 m.  
Figure 15: Diagram of coal machine speed change when the buried depth of fully-mechanized mining face is more than 200 m.  
When the burial depth is less than 200 m, organize the attack normally. The periodic weighting step is about 12.58 m. The overall intensity of periodic pressure is weakened, with pressure of generally 35-40 MPa, and less exceeding 40 MPa.