## 3 Study of the Floor Heave in Gob-Side Entry Retaining
### Simulation Results
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**GSI**} & \multirow{2}{*}{**D**} & **Compressive Strength (MPa)** & **Transile Strength (MPa)** & **Deformation Modulus (GPa)** & **Poisson’s Ratio** & **Cohesion Value (MPa)** & **Angle of Internal Friction (deg)** & **Dilatancy Angle (deg)** \\ \hline \multicolumn{8}{c}{Main roof (sandy mudstone)} \\ \hline
52 & 0.5 & 1.75 & 0.09 & 1.19 & 0.3 & 2.83 & 24 & 24 \\ \hline \multicolumn{8}{c}{Immediate roof (sandy mudstone)} \\ \hline
52 & 0.5 & 1.48 & 0.08 & 0.97 & 0.3 & 2.45 & 27 & 27 \\ \hline \multicolumn{8}{c}{Coal seam c\({}_{11}\)} \\ \hline
35 & 0 & 0.32 & 0.006 & 0.22 & 0.3 & 1.13 & 20 & 20 \\ \hline \multicolumn{8}{c}{Immediate floor (mudstone)} \\ \hline
47 & 0.5 & 0.87 & 0.04 & 0.50 & 0.3 & 1.61 & 22 & 22 \\ \hline \multicolumn{8}{c}{Main floor (sandstone)} \\ \hline
55 & 0.5 & 2.90 & 0.11 & 1.80 & 0.3 & 3.90 & 34 & 34 \\ \hline \multicolumn{8}{c}{Filling wall material} \\ \hline
66 & 0.5 & 3.62 & 0.16 & 1.48 & 0.3 & 3.33 & 29 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Rock mass and filling wall material parameters for numerical simulation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Primary Support**} & \multirow{2}{*}{**Type of Elements**} & **Material** & **Elastic Modulus** (GPa)** & **Poisson’s Ratio** & **Yield Strength** (MPa)** & **Tangent Modulus (GPa)** \\ \hline U-shaped steel & Beam &
\begin{tabular}{c} Bilinear isotropic \\ hardening \\ \end{tabular} & 200 & 0.27 & 295 & 52.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Steel arch frame parameters for numerical simulation. model, pseudoplastic deformation is accepted for analyzing the behavior of rock mass beyond the elastic stage, including discontinuous rock. The contour of the vertical expansion zone with post-peak strain is shown in Figure 5c. The positive strain scale in the figures is limited to \"+0.05\". All strains that are greater  
Figure 5: Stress–strain distributions around the gob-side entry retaining: (**a**) vertical stress; (**b**) horizontal stress; (**c**) vertical strain; (**d**) horizontal strain. Figure 6: Shear stress (**a**) and shear strain (**b**) distributions around the gob-side entry retaining. than +0.05 are indicated in gray. Vertical strains in this zone exceed the post-peak strain for mudstone by more than two times. In this zone, post-elastic deformation and delamination of rocks occur. Zones of horizontal post-peak expansion of rocks are formed under the filling wall body and coal seam body. In these zones, dilatancy expansion of rock is observed under the influence of high vertical stresses (Figure 5d). The expansion of rocks in these zones leads to compression of the rocks between them, underneath the entry span. The post-peak horizontal compression zone is shown in Figure 5d. Dilatancy in this zone is caused by the horizontal stresses. Zones of post-peak horizontal strains also form in the side walls of the entry. This causes deformation of the legs of the steel arch frame. The stress asymmetry not only leads to floor heave asymmetry but also irregular curvature of the support frame, which confirms the results of in situ observations in the gob-side entry retaining. Analysis of Figure 5 shows that counter-movements of rocks occur on the entry floor. Such movements cause shear deformations. Therefore, to analyze them, the distributions of shear stresses and strains in the surrounding rocks are shown in Figure 6. The main interest in this study is the central high-shear zone that occurs between the zone of uplift and the zone of subsidence of the immediate floor. This zone originates in the corner of the filling wall body and extends into the depth of the entry floor at an angle (Figure 6a). The post-peak shear strain zones are shown in Figure 6b.