Why in news?

• Efforts to release 41 workers trapped in the collapsed Silkyara-Barkot tunnel faced another major setback when the auger joint of the machine drilling through the debris broke.
• As a result, the rescuers spent the last two days cutting through the blade stuck inside the rescue pipes and removing it piece by piece.
• The rescuers are now planning to drill through the remaining few meters using the practice of rat-hole mining.

What’s in today’s article?

• Horizontal auger machine
• Rat-hole mining

Horizontal auger machine

• About
  • A horizontal auger machine is often called a horizontal boring machine or directional drill.
  • It is a specialised tool to create horizontal bores or underground tunnels without disturbing the surface.
  • It typically consists of a rotating helical screw blade called an auger, attached to a central shaft or drill, which penetrates the material by rotating.
  • These machines are commonly employed in construction, utility installations such as laying pipes or cables, and infrastructure projects.
• Working
  • For the machine to work, it is positioned at the starting point of the bore, usually on the surface.
  • It consists of a drill head with an auger or a drill string attached to it.
  • The auger at the front of the machine rotates and cuts through the soil, rock, or other materials underground.
    • Hydraulic or mechanical systems power this rotation.
  • As the auger advances, it removes the material from the tunnel, and it is usually flushed out by a drilling fluid or mud pumped through the drill string.
  • This fluid serves to lubricate the drilling process, cool the cutting head, and carry excavated material back to the surface.

What is rat-hole mining?

• About
  • It is a method of extracting coal from narrow, horizontal seams, prevalent in Meghalaya.
  • The term “rat hole” refers to the narrow pits dug into the ground, typically just large enough for one person to descend and extract coal.
  • Once the pits are dug, miners descend using ropes or bamboo ladders to reach the coal seams.
  • The coal is then manually extracted using primitive tools such as pickaxes, shovels, and baskets.
• Types
  • Rat-hole mining is broadly of two types.
  • In the side-cutting procedure, narrow tunnels are dug on the hill slopes and workers go inside until they find the coal seam.
    • The coal seam in hills of Meghalaya is very thin, less than 2 m in most cases
  • The other type of rat-hole mining is called box-cutting.
    • In this type, a rectangular opening is made, varying from 10 to 100 sqm, and through that a vertical pit is dug, 100 to 400 feet deep.
    • Once the coal seam is found, rat-hole-sized tunnels are dug horizontally through which workers can extract the coal.
• Environmental and safety concerns
  • The mines are typically unregulated, lacking safety measures such as proper ventilation, structural support, or safety gear for the workers.
  • Additionally, the mining process can cause land degradation, deforestation, and water pollution.
  • This method of mining has faced severe criticism due to its hazardous working conditions, environmental damage, and numerous accidents leading to injuries and fatalities.
  • Despite attempts by authorities to regulate or ban such practices, they often persist due to economic factors and the absence of viable alternative livelihoods for the local population.

When was it banned, and why?

• The National Green Tribunal (NGT) banned the practice in 2014, and retained the ban in 2015.
• The NGT observed, “It is also informed that there are umpteen number of cases where by virtue of rat-hole mining, during the rainy season, water flooded into the mining areas resulting in death of many individuals including employees/workers.”
• The order was in connection with Meghalaya, where this remained a prevalent procedure for coal mining.