Subsurface Environmental Engineering

ENGIN3502 Subsurface Environmental Engineering

Requirements about the report:

1. Individual formal academic report.
2. Adequate citations are mandate. Please note “Copy and Paste” is plagiarism (please refer to the course description on Moodle for details).  
3. Submit on or before the due date through Moodle. Penalty applies for late submission (please refer to the course description on Moodle for details).

Part 1: Blast fume Clearance and workplace re-entry times

Explosives that contain nitrogen, normally in the form of ammonium nitrate, can produce oxides of nitrogen, commonly called fume. With modern ANFO, the amount of toxic gases or fumes produced from blasting varies according to the explosive mix. There have been many single fatalities over generations of underground mining due to workers being gassed by toxic blasting fumes or an irrespirable atmosphere after re-entering the area that was blasted.

Determine safe parameters for safe re-entry after development blasting in a mine using the following input data:  

Face dimensions H= 5.2 m., W=5.8 m

Face advance 3.4 m

Length of development before blast 220m

Blasted material: middle density slate (use Table 1.)

ANFO factor = 2.45 kg/m3 slate broken

Face ventilation = 28m3/s

NO2 gas production rate = 3.4 kg per tonne of ANFO

NO2 TWA is 3 ppm (0.0003%).

Determine the following:

1. Volume of rock to be blasted
2. Tonnes of rock to be blasted
3. ANFO used (with modern explosives, the amount of toxic gases or fumes produced from blasting varies according to the explosive mix)
4. Fume throw back distance
5. Volume of fumes immediately after the blast
6. Volume of NO2 gas produced
7. Concentration of NO2 in fume throw back zone immediately after the blast
8. Concentration of fumes after they have spread throughout the drive but before they have entered the decline
9. Time for diluted fumes to fill the drive
10. Time for fumes to be diluted below TWA concentration
11. Total time for fumes to clear
12. No work will resume in the blast area until a post-blast examination has completed. What is the most important parameter to be examined?

Table 1. Swell factors for some materials

Example: after excavation of 300 m3 clay with bulking factor 40% - the clay swells to

Part 2: VentSim Model 

In this mine three sub-level caving levels will be active at any one time. In the model provided these are levels 1, 2 and 3.

The odd number levels subsequently are mirror images of level 1 and the even numbered ones mirror images of level 2. Ore from the sublevel drives is mucked out to an orepass and passed down to the loading level where it passes through a crusher and then onto a conveyor system located in a straight decline up to surface. In addition, there is an intake and return shaft as well as an access decline to surface

The objective of this exercise is to develop a ventilation strategy to ensure safe working in the mine. Use Ventsim model and by using a fixed quantity fan in the exhaust shaft circulating 260 m3/s ensure that flow occurs to all areas of the mine except in the level production drives, suggest using a 3 kPa fan to begin with. Add ventilation control devices as needed to ensure flow to all levels of the mine.

Part 3. VentSim Report 

Use the model developed in Part 2. The mine runs fleet of diesel equipment listed in Table 2.

In addition, if diesel equipment is not in use a minimum air velocity of 0.5 m3/s is required in airways. Where diesel equipment is in use employ the airflow requirement of 6 m3/s per 100 kW of rated power.

You are to design and model in Ventsim the following:

1. Fan and duct ventilation for the “dead end” drives on levels 1, 2 and 3, use 1.2 m diameter flexible ducting a forced ventilation system and the fans shown in Figure 2
2. Determine the main mine fan requirements to ventilate the mine using the fan as shown in Figure 3, this will involve determining the fan site, number of fans, are parallel fans needed etc.
3. The maximum air velocity allowed in the access decline is 5 m/s and in the conveyor decline 4 m/s (due to dust issues)

Submit a report on your findings, detailing any assumptions made, details of the modelling including Ventsim files and other calculation