## 3 Results and Analysis
### Theoretical Analysis
#### 3.3.2 Evaluation of the Applicability of the Model  
The overburden height \(H\) of the downward drift cut-and-fill stopping mining method is the product of the height \(h\) of the filled individual stopes and the number of filling layers \(m\). Taking the stopes of the third mining area of Jinchuan Group as an example, the overburden filling body has a capacitance \(\gamma\) of 20 KN/m\({}^{3}\), an internal friction angle \(\varphi\) of 31\({}^{\circ}\) and a cohesion force of 1180 KPa, and the load on the CPB roof is obtained by substituting Equations (2)-(5) as shown in Figure 5a. From Figure 5a, it can be seen that the load values obtained based on [PERSON] theory of ground pressure are constant, which is because the effect of filling body height is not considered in this theoretical model. The load value obtained based on the Terzaghi bearing capacity theory increases with the increase in the number of layers of the filled body and then stabilizes, but the load value is negative, which is due to the fact that the theoretical model is affected by the cohesive force. The load value obtained based on the Biebermann pressure theory increases and then decreases with the increase in the number of layers of the filling body, which is not consistent with the actual situation. The load value obtained based on the Classical Janssen pressure theory increases with the increase in the number of layers of the filling body and then stabilizes, which is consistent with the conclusions obtained from the previous studies [48; 49; 50; 51]. Therefore, the load values calculated based on Classical Janssen pressure theory are more suitable for the actual law.  
The relationship between the number of layers of different filling bodies and the load on the filling body is obtained after substituting the relevant parameters of 48\(\#\) and 40\(\#\) slopes into Classical Janssen pressure theory (see Figure 5b). From Figure 5b, it can be seen that the load on the CPB roof reaches the limitation when the number of layers of the filling body is 60. When the number of layers of the filling body exceeds 60, the load no longer changes. The calculated extreme values of the loads on the CPB roofs of the 48\(\#\) and 40\(\#\) slopes are 0.228 MPa and 0.231 MPa, respectively, which are close to the measured values in the field. This indicates that the load on the filling body calculated by the Classical Janssen pressure theory is more reasonable.  
Figure 5: Results of load calculation: (**a**) comparison of each theory, (**b**) calculation results of experimental slopes, (**c**) effect of slope size on load, (**d**) effect of physical and mechanical parameters of the filling body on load.  
The effects of different factors on the loads applied to the CPB roof are shown in Figure 5c,d. As the span of the stope increases, the load on the CPB roof shows a linear increase. When the span of the slopes is expanded from 3 m to 9 m, the load on the CPB roof is increased by 164%. As the length of the stope increases, the load on the CPB roof tends to increase rapidly and then stabilize. When the length of the stope exceeds 150 m, the load on the CPB roof reaches the extreme value. As the capacity of the filling body increases, the load on it tends to increase linearly. When the capacity is increased from 10 KN/m\({}^{2}\) to 40 KN/m\({}^{2}\), the load value is increased by 299%. With the increase in the friction angle in the filling body, the load on the CPB roof tends to decrease gradually. The above results are basically in agreement with the previous studies.