## 4 Field Application of GSCRF
### Surrounding Rock Control Scheme  
#### 4.2.1 Road Support Scheme  
The 1510 track gateway has an excavation width \(W_{e}\) of 4.0 m and a net width \(W_{n}\) of 3.8 m and is supported by anchor nets (cables). The roadway is supported by 8# cold-drawn wire woven metal nets (sized 60 \(\times\) 60 mm) across the whole section, with 2100 mm long \(\Phi\)20 mm resin anchor bolts for the roof, and 2100 mm long \(\Phi\)18 mm full thread anchor bolts for the sides. Bolt plates sized 150 \(\times\) 150 mm (length \(\times\) width) are 10 mm thick steel plates pressed into an arc shape. The row spacing of the anchor bolts is 950 \(\times\) 1000 mm for the roof (center-to-center) and 1000 \(\times\) 1000 mm for the sides (center-to-center). The torque of the anchor bolts \(t_{ar}\) is a minimum of 200 Nm for the roof and 150 Nm for the sides. The diameter of the anchor cable is 18 mm, the length is 6 m, the spacing is 1400 mm, the row spacing is 3 m. These cables are installed in groups of 2 and supported by 500-600 mm 11# I-steel cable beams pretensioned to the design value of 200 KN. According to theoretical analysis and field investigation, with the advancement of the working face, the immediate roof rock will fall in time, and it can basically fill up the gob. Under such conditions, since there is almost no free space below when the main roof rock beam rotates and sinks, its movement is slow and gradual, and will not impact the slope support or the roadside support body of the gob-side retained roadway. Therefore, the pressure on the roadside support or the anchor-net-cable support is mainly from the immediate roof. That is, the main function of the roadside support or the anchor-net-cable support is to directly hold or hang the immediate roof, so that it is closely combined with the main roof rock and can collapse and sink together with the main roof rock beam until the main roof rock beam touches the gauge and gradually compacts the gauge in the gob. According to the support principle model, the function of anchor cables for the roof is to suspend the immediate roof rock tightly on the main roof rock so that the immediate roof will not break away from the main roof and sink alone. The 1510 track gateway was originally supported by anchor nets (cables), and the strength of the roof metal nets cannot meet the requirements of roof protection during the roadway forming period. Thus, to ensure the safety of the roof, it was necessary to install new nets (rhombic metal nets) and additional anchor cables during roadway forming. After comprehensive consideration, we decided to reinforce the roof by \"one steel tape + three cables\" alternately with \"one beam + three cables\". In order to track the support effect, it is also necessary to analyze and check the force of M-tapes. The bottom view of the M-tape arrangement is shown in Figure 10.  
Figure 10: Bottom view of M-tape arrangement. As M-tapes are generally exposed to breakage failure, the tensile strength needs to be checked. Assume the spacing of M-tapes is 1 m and all the weight of the rock underlying the anchor point is carried by the M-tape, then the pressure of the M-tape in the vertical direction [40] is:  
\[ \begin{array}{ll}P&=\frac{\rho_{l}\times H\times D}{5}\\ &=\frac{2.5\frac{1}{m^{3}}\times 8\;\mathrm{m}\times 1\;\mathrm{m}}{0.137\; \mathrm{m}}\\ &=1.46\;\mathrm{MPa}\end{array}  \tag{3}\]  
where: \(P\)--the pressure of the M-tape in the vertical direction, Pa; \(\rho_{l}\)--test weight, taken as 2.5 t/m\({}^{3}\); \(H\)--height of the immediate roof, m; \(D\)--tape spacing, m; \(S\)--tape width, m.  
Then, the tension force on the M-tape [40] is:  
\[ \begin{array}{ll}F&=P\times S\times L\\ &=1.46\;\mathrm{MPa}\times 3.2\;\mathrm{m}\times 0.137\;\mathrm{m}\\ &=640\;\mathrm{kN}\end{array}  \tag{4}\]  
where: \(F\)--tension force, kN; \(L\)--tape length, m.  
The breaking force of M-tape is generally 350 kN. Obviously, the breaking force of one layer of M-tapes is less than the load of 640 kN.