## 4 Floor Heave Control with Anti-Shear Pile Technology
### Filling Pile Floor Support Scheme  
The analysis of monitoring of gob-side entry retaining shows that the main gateroad stability problem is dramatic floor heave. Therefore, the modification of the current support system of the entry is necessary.  
Based on numerical simulation results, it was found that the most effective floor support scheme is the 2 pile 5+2 (B-60) scheme. Additional installation of piles in the original support system was proposed. The rationale for the effectiveness of this scheme is presented in the previous section of this paper. Figure 18 shows the proposed design of the support scheme. Drilling of boreholes for piles into the entry floor can be carried out with a machine for drilling degassing wells. SBG-1M is an example of such a machine.  
According to the authors, the proposed anti-shear pile technology does not require significant investment. Investments are required to purchase an SBG-1M-type drilling machine. The approximate cost of such equipment in Ukraine, taking into account transportation costs, is EUR 15,000. Taking into account the service life, residual value, average monthly depreciation, and downtime, the depreciation expense will be EUR 205/month. The machine repairs and maintenance expenses, taking into account planned repairs, are 0.012 man-hours. Taking into account wages in Ukraine, monthly maintenance expenses will be EUR 119/month. Electric energy consumption and the salary of a worker operating the drilling machine depend on local wages and the quantities of drilling work. Three workers per shift are involved in the implementation of the proposed technology.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Scheme**} & \multirow{2}{*}{**Pile Type**} & \multirow{2}{*}{\begin{tabular}{c} **Class of** \\ **Concrete in** \\ **the Pile** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Cost of** \\ **Concrete, EUR** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Cost of Tube,** \\ **EUR** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Cost of Tube,** \\ **Reinforcement, EUR** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Cost of** **and Lateral** \\ **Reinforcement, EUR** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Total Cost,** \\ **EUR** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Maximal Floor** \\ **Heave, mm** \\ \end{tabular} } \\ \hline
2 pile 5+2 & Steel pile & B-60 & 9.35 & 116.81 & & 126.16 & 361 \\ \hline
2 pile 5+2(tube) & Steel tube & - & - & 116.81 & & 116.81 & 399 \\ \hline
2 pile 5+2(B-20) & Filling pile & B-20 & 8.48 & - & 25.92 & 34.40 & 397 \\ \hline
2 pile 5+2(B-40) & Filling pile & B-40 & 8.78 & - & 25.92 & 34.70 & 389 \\ \hline
2 pile 5+2(B-60) & Filling pile & B-60 & 9.35 & - & 25.92 & 35.27 & 386 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of the costs of materials for different types of piles with scheme 2 pile 5+2.  
Figure 17: The vertical strain distributions around the gob-side entry retaining after pile installation with schemes (a) 2 pile 5+2(tube); (b) 2 pile 5+2(B-20); (c) 2 pile 5+2(B-60).  
Pile installation must be carried out after the roadway excavation stage, and before the longwall mining stage. Therefore, the production schedule of the working face does not affect the schedule of pile installation. The estimated pace of installation of piles in a gateroad in a three-shift operating mode is 819 m/month.