# Strata Control by Roof Blasting for Bord and Pillar Mining Method in Mechanized Depillaring Panels
## 4 Numerical Simulation
### Simulation of Proposed Panels
#### 4.1.2 Simulation for Estimation of RLH at Different Places in the Panel  
The geometry of the generated model is 229.5 m, 271 m, and 102 m along the length (x-axis), width (y-axis), and height (z-axis), respectively, including 50 m floor (Figure 19), considering the hardware constraint (memory and runtime) of a computer. This model is incorporated with the existing geo-mining conditions and rock mass properties. The thickness of the coal seam considered in the model is 1.8 m, developed and depillared to full height. A truncated load (0.025 MPa/m \(\times\) 214 m) is applied over the top of the model for the left-out unmodelled roof of 216 m. The width of original/split galleries is kept at 5.5 m, respectively. The bottom and four side walls of the model are fixed, while the top one is kept free as boundary conditions. The properties of rock mass used in the models are collected from the mines and tested in the laboratory, as mentioned in Table 7. Initially, the in situ model is developed as per the abovementioned geometry at a depth of 266 m, followed by the development of pillars and galleries, as per BPMM. This model is then depillared following a straight line of extraction (Figure 20). The height of the rock load to be supported by the roof bolt is estimated for the development and depillaring operation. Here, RLH is defined as the height of the roof strata up to the safety factor contour value of 1.0 in the model, which needs artificial support. RLH is measured at different locations, which is shown in Figures 20 and 21. Support design for the panel on the basis of numerical modeling study is given in Figure 9. RLH is measured at a distance of 1.0 m outby from the goat edge (Figure 21) without using applied support in the model, which is found to be 1.5 m (3.75 t/m\({}^{2}\))  
Figure 20: Manner of pillar extraction, their sequence and locations marked for measurement of RLH in the numerical model for the design of support system at the goaf edge in panel.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Strata** & **Constitutive Model** & **Thickness (m)** & **Young’s Modulus (GPa)** & **Shear Modulus (GPa)** & **Bulk Modulus (GPa)** & **Poisson’s Ratio** & **Density** & **RMR for FOS** & **Compressive Strength (MPa)** & **Tensile Strength (MPa)** \\ \hline Layer 1: & & & & & & & & & & & \\ Floor & Elastic & 50.0 & 7.00 & 2.80 & 4.67 & 0.25 & 2500 & 50.40 & 50.00 & 5.00 \\ (FGSST) & & & & & & & & & & \\ Layer 2- & Elastic & 1.8 & 2.00 & 0.80 & 1.34 & 0.25 & 1400 & 50.40 & 23.00 & 2.30 \\ Coal & Layer 3: & & & & & & & & & \\ Layer 4- & & & & & & & & & & \\ MGSST & & & & & & & & & & \\ Layer 5: & & & & & & & & & & \\ Carbona- & Elastic & 3.0 & 2.50 & 1.00 & 1.67 & 0.25 & 1800 & 50.40 & 30.00 & 3.00 \\ (FOSST) & & & & & & & & & & \\ Layer 6: & & & & & & & & & & \\ Roof & Elastic & 12.0 & 7.00 & 2.80 & 4.67 & 0.25 & 2500 & 50.40 & 50.00 & 5.00 \\ (FGSST) & & & & & & & & & & \\ Layer 6: & & & & & & & & & & \\ Roof & Elastic & 32.0 & 5.00 & 2.00 & 3.33 & 0.25 & 2200 & 50.40 & 40.00 & 4.00 \\ (MGSST) & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 7: Constitutive model selection and physico-mechanical properties of strata used in numerical modeling of panel.