Underground Coal Mining

Explain the characteristics and composition of coal measure rocks and their influence on underground mining operations. (7)

A coal seam is at a depth of 600 meters and the overburden rock has an average density of 2.5 g/cm³. Calculate the vertical stress acting on the coal seam due to the overburden. Based on the stress value, analyze which underground mining method (Bord and Pillar or Longwall) would be more suitable. Justify your answer. (7)

Compare and contrast Bord and Pillar, Longwall and Shortwall mining methods in terms of efficiency, applicability and safety. (7)

For a given mine layout, you need to maximize coal extraction while ensuring safety. The options for panel layouts are:

1. Option A: Smaller panels with larger pillars
2. Option B: Larger panels with smaller pillars
3. Option C: A combination of shortwall mining with Bord & Pillar

Which option would you choose for an underground coal mine located in an area prone to roof collapses? Explain your reasoning with numerical analysis. (7)

1. विकल्प A: छोटे पैनल और बड़े पिलर
2. विकल्प B: बड़े पैनल और छोटे पिलर
3. विकल्प C: शॉर्टवॉल खनन और बोर्ड एंड पिलर का संयोजन

Explain the importance of pillar size, heading dimensions and panel design in the Bord and Pillar method. (7)

A Longwall panel has the following requirements:

1. Methane emission rate: 15 m³/min
2. Air velocity at the face: Minimum 2 m/s
3. Panel width: 250 meters
4. Ventilation efficiency factor: 0.85

Calculate the minimum airflow required and determine whether a bleeder ventilation system or a U-tube ventilation system would be more suitable for the given conditions. (7)

1. मीथेन उत्सर्जन दर: 15 m³/min
2. फेस पर वायु वेग: न्यूनतम 2 m/s
3. पैनल चौड़ाई: 250 मीटर
4. वेंटिलेशन दक्षता कारक: 0.85

Compare V, diagonal and straight front methods for panel development in the Bord and Pillar system. (7)

A Bord and Pillar panel is being depillared using:

1. Conventional method: 8 m advance per shift, coal loss 25%
2. Mechanized method: 12 m advance per shift, coal loss 18%

If the total panel size is 500 m × 300 m, calculate the total coal output difference and suggest whether mechanized depillaring justifies its cost in a scenario where equipment investment is 30% higher than conventional methods. (7)

1. पारंपरिक विधि: 8 मीटर प्रति शिफ्ट, कोयला हानि 25%
2. मशीनीकृत विधि: 12 मीटर प्रति शिफ्ट, कोयला हानि 18%

What are the key factors determining the size of a Longwall panel? (7)

A Longwall panel has a face length of 250 meters and operates two shifts per day.

1. If the target production is 5000 tons/day and the specific cutting energy required is 15 MJ/ton, what should be the daily advance rate in meters?
2. Suggest modifications to enhance daily advance while keeping energy consumption minimal. (7)

1. यदि लक्ष्य उत्पादन 5000 टन/दिन है और विशिष्ट कटिंग ऊर्जा (specific cutting energy) 15 MJ/ton है, तो दैनिक अग्रिम दर (advance rate) मीटर में क्या होनी चाहिए?
2. ऊर्जा खपत को न्यूनतम रखते हुए दैनिक अग्रिम दर को बढ़ाने के लिए सुझाव दें।

Describe the gate, goaf and face area support systems used in conventional and fully mechanized Longwall mining. (7)

Discuss the modifications of the Room and Pillar method for deep-seam mining. (7)

Compare Bord and Pillar, Longwall, Room and Pillar and Shortwall mining methods based on coal recovery, operational efficiency and safety. (7)

Classify the different methods of goaf stowing and describe their working principles. (7)

During depillaring, a panel with an initial coal reserve of 80,000 tons is extracted using a simultaneous development and depillaring scheme. The recovery efficiency is 70% and the daily production is 1,200 tons. Calculate:

1. The total coal extracted.
2. The time required to complete depillaring.
3. The percentage of coal left in the goaf. (7)

1. कुल कोयले की मात्रा
2. डिपिलिरिंग को पूरा करने में लगने वाला समय
3. गोफ में शेष कोयले का प्रतिशत

Discuss the factors that influence the division of a mine area into panels and districts. How does this division affect the overall efficiency of mining operations? (7)