## 3 Gangue-Side Lateral Pressure-Control Technology
### Design of the Numerical Model for the Cutting Roof Scheme  
#### 3.3.1 Analysis of the Impact of Cutting  
As analyzed previously, the lateral loading strength of the roadway-side support in the gob-side entry retaining system is not only related to the mechanical properties of the surrounding rock (such as \(\mathbf{E_{0}}\), \(\mathbf{h_{j}}\), \(\mathbf{\beta}\), \(\mathbf{\phi_{6}}\), etc.) but also strongly influenced by the movement state of the overlying strata during mining (such as \(\mathbf{\varphi_{1}}\), \(\mathbf{l_{s}}\), etc. ), mining height, and the bearing capacity of the gangue in the gob. To effectively reduce the lateral loading on the roadway-side support during the mining process, the pre-splitting top-cutting technique can be employed to mitigate the impact of the roof rotation during mining [38]. By severing  
Figure 16: Vertical displacement distribution of model mining face. Figure 15: Vertical stress distribution of mining face. the lateral basic roof of the roadway, the cantilever length of the roof is reduced, and the roof strata outside the cut line in the gob can collapse and fill the gob in time, forming a cushion layer. This reduces the rotational displacement space of the upper basic roof, decreasing its rotational angle, and it allows the roof strata to quickly transfer the load to the gob, thus forming a stable structure. As shown in Figure 17, by severing the stress transmission between the overlying strata in the gob and the roof of the entry, when the hydraulic supports are pulled forward, the roof loses its support and rapidly collapses into the gob. To verify the effectiveness of the top-cutting technique, the simulation results of the vertical stress in the gob-side entry retaining surrounding rock and the vertical displacement of the roof during its movement were analyzed. A FLAC3D numerical model was constructed to simulate the pre-splitting top-cutting interface, for which the interface parameters were adjusted to increase their strength and stiffness so that they are significantly higher than the surrounding rock in the roadway. This simulates the effect of blocking stress transmission along the structural plane. Additionally, the \"update\" parameter for the interface is set to \"off\" [39], preventing the surface from moving after the structure is disturbed and avoiding the search for new contact points. This simulates the separation of nodes and discontinuous deformations such as the sliding and opening of the roof structure after the top-cutting process. The results are shown in Figures 18-20. Figure 17: Movement law of overburden strata and falling waste rock in gob-side entry before and after roof cutting: (a) before cutting; (b) after cutting. Figure 18: Curve of tunnel roof and floor displacement before and after roof cutting. The curve of the roof and floor displacement before and after top-cutting is shown in Figure 18. In the case without top-cutting, the roof displacement remains almost unchanged at a distance of 35 m in front of the working face. However, behind the working face, at distances of 0-40 m, the displacement begins to increase slowly; at distances of 40-80 m behind the working face, the displacement increases rapidly, with the maximum displacement reaching 455 mm. When the top-cutting gob-side entry retaining technology is used, the maximum displacement of the roof and floor stabilizes at 282 mm, significantly reducing the maximum displacement by 38.02%. Figures 19 and 20 show the lateral horizontal stress distribution in the gob-side entry retaining support body and the internal elastic-plastic region changes before and after top-cutting. The fallen gangue, under the influence of the self-weight of the overlying rock layers, generates lateral horizontal stress along the working face's direction during the crushing and compaction process, which exerts compressive forces on the roadway-side support. The lateral load distribution is generally \"saddle-shaped\".