## 4 Floor Heave Control with Anti-Shear Pile Technology  
### Design and Parameters of Floor Heave Control Schemes  
The analysis of stresses and strains given in the previous section showed that the key factor of floor heave in gob-side entry retaining is the transmission of stresses from under the filling wall body to the zone under the entry span, which causes delamination, vertical expansion, and uplift of the discontinuous rocks in the immediate floor. A reinforcement method with anti-shear pile installation was proposed for the floor heave control. The study of the effectiveness of the anti-shear pile was carried out in three stages. In the first stage, three floor heave control schemes with one anti-shear pile were studied. Each scheme was simulated twice: with a pile length of 2 m and 4 m. The distance between piles was equal to the distance between steel arch frames. Figure 7a-f show the support schemes that were studied. The parameters of the schemes are presented in Table 3.  
In the second stage, three floor heave control schemes with two anti-shear piles were modeled. The length of each pile was 2.0 m. Thus, the summary pile length in the first simulation stage and in the second simulation stage was equal. Schemes of the second simulation stage are shown in Figure 7g-i. In the third simulation stage, the investigation of the optimal type of pile was carried out. In this case, a comparison of three pile types was conducted:  
* \"Steel pile\"--steel tube with a diameter of 200 mm and a wall thickness of 4 mm, filled with concrete (for this type of pile, two previous simulation stages were performed);
* \"Steel tube\"--steel tube with a diameter of 200 mm and a wall thickness of 4 mm;
* \"Filling pile\"--a pile of reinforced concrete (simulation was carried out for concrete classes B-20, B-40, and B-60). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Scheme**} & \multirow{2}{*}{\begin{tabular}{c} **Number of** \\ **Piles** \\ \end{tabular} } & \multirow{2}{*}{**Pile Position**} & \multirow{2}{*}{\begin{tabular}{c} **Pile Length** \\ **(m)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Summary** \\ **Length of** \\ **Files (m)** \\ \end{tabular} } & \multirow{2}{*}{**Pile Type**} & \multirow{2}{*}{\begin{tabular}{c} **Class Of** \\ **Concrete in** \\ **the Pile** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Deformation** \\ **Modulus** \\ **(GPa)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Poisson’s** \\ **Ratio** \\ \end{tabular} } \\ \hline \multicolumn{8}{c}{1 st simulation stage} \\ \hline
1 pile 5 (4) & 1 & \#5 & 4 & 4 & Steel pile & B-60 & 72 & 0.25 \\ \hline
1 pile 4 (4) & 1 & \#4 & 4 & Steel pile & B-60 & 72 & 0.25 \\ \hline
1 pile 3 (4) & 1 & \#3 & 4 & 4 & Steel pile & B-60 & 72 & 0.25 \\ \hline
1 pile 5 (2) & 1 & \#5 & 2 & 2 & Steel pile & B-60 & 72 & 0.25 \\ \hline
1 pile 4 (2) & 1 & \#4 & 2 & 2 & Steel pile & B-60 & 72 & 0.25 \\ \hline
1 pile 3 (2) & 1 & \#3 & 2 & 2 & Steel pile & B-60 & 72 & 0.25 \\ \hline  & \multicolumn{8}{c}{2 nd simulation stage} \\ \hline
2 pile 5+1 & 2 & \#5, \#1 & 2 & 4 & Steel pile & B-60 & 72 & 0.25 \\ \hline
2 pile 5+2 & 2 & \#5, \#2 & 2 & 4 & Steel pile & B-60 & 72 & 0.25 \\ \hline
2 pile 5+2(tube) & 2 & \#5, \#2 & 2 & 4 & Steel tube & - & 200 & 0.3 \\ \hline
2 pile 5+2(B-20) & 2 & \#5, \#2 & 2 & 4 & Filling pile & B-20 & 27.5 & 0.19 \\ \hline
2 pile 5+2(B-40) & 2 & \#5, \#2 & 2 & 4 & Filling pile & B-40 & 36.0 & 0.19 \\ \hline
2 pile 5+2(B-60) & 2 & \#5, \#2 & 2 & 4 & Filling pile & B-60 & 39.5 & 0.19 \\ \hline \end{tabular}
\end{table} 
Table 3: The parameters of floor heave control schemes for numerical simulation. The plan of the numerical experiment is presented in Table 3.  
The pile positions were numbered in the direction from the solid coal body to the filling wall body. The central pile (position #3) has a vertical orientation along the axis of the roadway cross-section. The piles that were installed in floor corners (position #1, position #5) were inclined 48 degrees to the horizon.