Mining is the heart of the operations
The Project has applied the technology of underground mining of the room and pillar techniques use as it is the method of highest safety standard and internationally accept
APMC has engaged ERCOSPLAN Ingenieugesellschaft GmbH, the world ranking for potash mining consultant, to complete the Extend Comprehensive Feasibility study for the Project in order to ensure all technical matters including environmental aspects as being a part of development stage. The study concluded that the most suitable underground mining techniques for the Project is the room and pillar which is the highest standard and internationally accepted over 150 years.
Room and Pillar techniques supports to control the decrease of the ground surface very well and backfill the ore tailings to the gap in underground mine which will increase strength and control surface subsidence, therefore the control of surface subsidence is well within acceptable standard that will not cause any damage to the project engineering structure and environment.
The Trial Mine
The Project has studied and trial mining by using room and pillar techniques, starting from drilling a declined tunnel for entering into underground mine zone, the details of trail mine are as follow:
● Drilling a slope tunnel size 6 X 3 meters, 935 meters long, with the slope of 1:5 and of 180 meters this was completed in 1997.
● Trail mining with room and pillar techniques with the width of 15 meters, 25 meters height, 60 meters long and along with the pillar width of 20 meters, for self-support 3 slopes (Completed in 1999).
● Then, it installed a monitoring station for surface subsidence at the trail mining area, the measured value from then up to now found the decrease of the land surface does not affect 1999 structure on the ground area of the experimented mine whatsoever. It confirms underground mining of the room and pillar method is suitable for the potash mining potash.
Underground Mining Method
Room-and-Pillars mining method is determined to be the most suitable mining method for the Bamnet Narong Potash Project, while the remaining of 1 in 3 is a highly safety standard with excavation of the ore on the average is just the pillars, so the tunnel is stronger to use as pillars. This method is acceptable and widely used.
Mining Techniques can be further categorized into 3 methods in accordance with seam thickness of ore as follows:
Method 1) Room and square pillar
It is suitable for the mining with the ore thickness between 3-8 meters by drilling to tumble down the ore in the horizontal direction. A tunnel is drilled with a room width of 20 m in parallel by spacing between the rooms by 400 m with the length of 15-20 m and tumble down the ore in traverse to connect the tunnel in these parallels. So it creates supportive pillars 20 m all around the ore production with the ore that is spaced out to support themselves.
Method 2 ) Room and pillar with additional benching
It is suitable for the mining with ore thickness between 8-15 meters. On the top of the ore layers may be drilled it tumbled down like the first method. After that it is left the bottom ore layer to be drilled down in the vertical direction by spacing the ore to do support as pillars as before, that can have the ore-producing room the same as using the room and pillar method, but the room height is higher.
Method 3 ) Room and pillar with long pillar
It is suitable for mining with ore thickness between 15 – 25 meters by drilling on the top by 2 m by developing the tunnel into 25 m. ore layer and the bottom tunnel is in parallel. When reaching the location to build an ore production room it shall be drilled to tumble down the ore. Then the ore is removed by using an ore loader. The ore production room has the width of 400 m, 15 -20 m long. It will leave the ore as the supportive pillars of x 400 m.