🔹 1. Introduction

Working under waterlogged areas, aquifers, rivers, lakes, tanks, or dams is extremely dangerous.
Many historical mine floods occurred because mining was carried out:

• Without studying old waterlogged workings
  
• Without probing
  
• Below rivers/lakes without proper safety measures
  
• Underlying dams/tanks without adequate barriers
  

DGMS enforces strict rules before any such mining is allowed.
🔹 2. Working Under Waterlogged Areas

These include:
✔ Abandoned workings
✔ Old galleries & goaf areas
✔ Unmapped workings
✔ Previous mine boundariesThese may contain large volumes of stagnant water, causing catastrophic inrush if breached.
⭐ 2.1 Mandatory Precautions When Approaching Waterlogged Workings(As per your document)Danger from water and Inundatio…✓ Detailed review of plans✓ Borehole probing ahead of face

• Horizontal
  
• Inclined
  
• Roof & floor holes
  
• At 1.5–3 m intervals
  

✓ Reduced rate of advanceFace should advance slowly and systematically.✓ Large cautionary zoneBetween 120 m and 60 m.✓ Supervised workings onlyMandatory presence of competent supervision.✓ No blasting near weak barriersHand-tool dressing allowed under supervision.

🔹 3. Working Below Surface Water Bodies (Rivers, Lakes, Ponds)Mining below water bodies is dangerous due to:

• Percolation of water through fractured strata
  
• Roof weakening
  
• Sudden collapse of strata
  

⭐ 3.1 DGMS Precautions
✔ 1. Minimum Cover RequiredHard strata cover must be sufficient to prevent breakthrough.✔ 2. Probe Holes MandatoryProbe holes must be drilled:

• Ahead of face
  
• On roof, floor, and sides
  
• In a fan-shaped pattern
  

✔ 3. Constant Water-Level MonitoringSurface water bodies (rivers, tanks) must be monitored daily.✔ 4. Barrier PillarsSpecial water barrier pillars left below the water body.✔ 5. No Working During Flood PeriodMining stops if:

• Tank/dam overflows
  
• River rises above danger level
  
• Monsoon flooding is predicted
  

🔹 4. Working Under Aquifers

An aquifer is a water-bearing permeable rock formation (sandstone, fractured limestone, gravel beds).Mining below aquifers is high-risk because inflow from aquifers can be continuous and high-pressure.
⭐ 4.1 Precautions While Working Beneath Aquifers✔ Adequate water-proof coverMinimum safe thickness determined by geology.✔ Dewatering of aquifer if possiblePumping wells or drainage boreholes.✔ GroutingInjecting cement slurry or chemicals to seal water-bearing zones.✔ Reduced face advance speedAdvance must be slow & controlled.✔ Continuous monitoring of inflowSudden rise indicates breakthrough.✔ Probe holes ahead & aboveRoof probing is compulsory.

🔹 5. Working Under Dams, Tanks & Reservoirs

These provide maximum risk, because a breach may release lakhs of cubic meters of water instantly into the mine.DGMS rules require:
✔ Special permission for mining under dams
✔ Double the normal barrier thickness
✔ Hydrogeological study
✔ Water-pressure testing
🔹 6. Safe Working Procedure (DGMS)

Step 1: Study Old WorkingsVerify the latest plan and conduct check surveys.

Step 2: Drill Probe HolesMultiple probe holes in front, roof, floor.

Step 3: Determine Safe Barrier ThicknessBased on water pressure & rock strength.

Step 4: Advance SlowlyFace advance not more than 1.2 m at a time in dangerous zones.

Step 5: Immediate Withdrawal if Water Starts DrippingNo risk permitted once seepage increases.
🔹 7. Hazards Associated with Waterlogged Zones

• Sudden inundation
  
• Airblast
  
• Roof collapse
  
• Floor heave
  
• Machinery loss
  
• Entrapment of miners
  

🔹 8. Text Diagram – Working Under Water Body
======================== Water Body (River/Lake) ||||||||||||||||||||||| Saturated Zone ------------------------ Impervious Layer (Barrier) | | | | | Working Face | <-- Probe Holes -->
🔥 25 MCQs (DGMS Pattern) with Answers
1) Waterlogged workings refer to —

a) Dry galleries
b) Fresh workings
c) Depillared areas
d) Old abandoned areas filled with water
e) None
Answer: d
2) Main danger of working under rivers —

a) Gas outburst
b) Noise
c) Water percolation and inrush
d) Less visibility
e) None
Answer: c
3) Probe holes are drilled to —

a) Check ventilation
b) Detect water ahead of face
c) Fix roof bolts
d) Charge explosives
e) None
Answer: b
4) Aquifers are —

a) Hard rocks
b) Igneous bodies
c) Permeable water-bearing formations
d) Roof supports
e) None
Answer: c
5) Barrier under water bodies must be —

a) Thin
b) Strong & adequate
c) Weak
d) Temporary
e) None
Answer: b
6) Fan-shaped drilling is used when —

a) Installing supports
b) Approaching waterlogged areas
c) Lighting
d) Ventilation
e) None
Answer: b
7) Advance under water bodies is —

a) Fast
b) Random
c) Slow and controlled
d) Without drilling
e) None
Answer: c
8) Grouting is done to —

a) Improve blasting
b) Seal water-bearing zones

c) Reduce dust
d) Seal airways
e) None
Answer: b
9) Sudden increase in water seepage means —a) Safe zone
b) Good ventilation
c) Imminent breakthrough
d) Better production
e) None
Answer: c
10) Working under dams requires —

a) Ordinary permission
b) Special DGMS permission
c) No permission
d) Manager’s signature only
e) None
Answer: b
11) Minimum safe cover under water bodies depends on —

a) Coal grade
b) Worker skill
c) Water pressure & rock strength
d) Ventilation
e) None
Answer: c
12) Danger sign when drilling probe holes —

a) Dry chips
b) Wet or dripping holes
c) Hard cores
d) Smooth walls
e) None
Answer: b
13) Old goaf areas may contain —

a) Empty voids
b) Large volumes of water
c) Gas only
d) Ore only
e) None
Answer: b
14) Aquifer pressure can cause —

a) Roof stability
b) Inrush and flooding
c) Better illumination
d) Low dust
e) None
Answer: b
15) Dykes can create water danger because —a) They are impermeable
b) They may trap water behind them
c) They support roof
d) They improve permeability
e) None
Answer: b
16) Advance under aquifers requires —

a) Horizontal drilling only
b) Roof, floor & side drilling
c) No drilling
d) Explosive testing
e) None
Answer: b
17) Dewatering wells are used to —

a) Store water
b) Lower water table
c) Increase humidity
d) Pump air
e) None
Answer: b
18) Roof collapse near water body leads to —

a) Better airflow
b) Massive inrush
c) Rock strengthening
d) None
e) Both a & c
Answer: b
19) Most important precaution under waterlogged areas —

a) More ventilation
b) Probe drilling
c) More explosives
d) High haulage
e) None
Answer: b
20) Barrier thickness is determined by —

a) Manager
b) Blaster
c) Survey & geology team
d) Timekeeper
e) None
Answer: c
21) Sudden water seepage indicates —

a) Safe zone
b) Imminent breakthrough
c) Dry strata
d) Recharge zone
e) None
Answer: b
22) Grouting uses —

a) Air
b) Paint
c) Cement slurry / chemicals
d) Sand only
e) None
Answer: c
23) Working under waterlogged areas requires —

a) High speed
b) Controlled blasting and slow progress
c) Only manual work
d) No supervision
e) None
Answer: b
24) Dams near mines must be —

a) Uninspected
b) Weak
c) Regularly inspected & maintained
d) Ignored
e) None
Answer: c
25) Main danger of aquifers is —

a) Gas outburst
b) Heat
c) High-pressure water inflow
d) Noise
e) None
Answer: c

                          🔚 Conclusion

Working under waterlogged areas, aquifers, rivers, lakes, and dams requires extreme caution.
DGMS mandates strict safety procedures including:

• Probe drilling
  
• Grouting
  
• Safe barrier thickness
  
• Reduced face advance
  
• Continuous monitoring
  

These precautions prevent sudden water inrush and ensure safe mining operations.

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