**3. Results**

This section presents the key findings from the block cave mine ventilation research study that provides valuable information for optimizing the ventilation systems. The findings include the results and observations from numerical simulation studies, scale model studies of the mature and immature block and panel cave mines, mathematical modeling, and field observations.

### **3.1 Finding 1: airgap and airflow resistance of an immature panel cave**

Airflow through an immature panel cave was analyzed under four different airgap heights using a 3D panel cave geometry model (**Figure 4a** and **b**). Furthermore, CFD simulations were performed to predict the radon emissions from an immature panel cave.

The analysis of the airflow patterns through the cave indicated that the size and intensity of the recirculation zones change with the change in airgap heights. CFD simulation results show that in the absence of undercut ventilation, radon concentrations in the production level were much lower than those observed when the undercut level was ventilated [13, 14]. This can be attributed to the creation of a low-pressure region in the undercut level, the porous nature of the cave, and the air recirculation (**Figure 5**) in the cave.

*Block Cave Mine Ventilation: Research Findings DOI: http://dx.doi.org/10.5772/intechopen.104856*

**Figure 4.** *(a) Model dimensions—Top view (meters). (b) Model dimensions—Front view (meters).*

## **3.2 Finding 2: cave porosity zone height decreases with an increase in rock mass strength**

Porosity values for different cave zones were predicted under both cave development and mature cave conditions using FLAC3D and PFC3D modeling, respectively. FLAC3D simulations were performed first to predict the formation of different zones in a typical block cave mine and then to investigate the effect of rock mass strength (RM) and production rate on the porosity of different cave zones in both block and panel cave mines.

Simulations were performed on two models for both block and panel cave cases by keeping all the model parameters the same except the properties of the rock masses. For both cases, production draw has been simulated with a total height of draw (HD) of 0.6 m by applying the downward velocity of 0.0001 m/s at all the grid points on the roof of the undercut. However, in the case of a panel cave simulation, the applied extraction rates are not the same at all the grid points. Simulated porosity values are shown in **Figures 6** and **7** for block and panel cave, respectively.

It can be seen from **Figures 6** and **7** that as the rock mass strength (RM) increases, the heights of the cave porosity zones decrease for both block and panel cave models. This is because the propagation rate decreases as rock mass strength increases. For both cases, the porosity value for the mobilized zone ranges from 0.35 to 0.40. Further, the zone heights for different cave zones are relatively higher for RM1 than RM2.

Similar trends were observed for the panel cave case, except that the cave zone profile is inclined toward the right due to the nature of the extraction for the panel cave mine.
