Revised DGMS Standards for Resin Capsules in Roof Bolting – Testing, Quality Control & 25 MCQs

🧾 DETAILED NOTES

1️⃣ Introduction

Roof bolting is the primary support system in Indian underground coal and metalliferous mines. Resin capsules are widely used as a rapid-setting, high-strength grouting material for anchoring roof bolts. DGMS has revised standards to ensure higher bonding strength, quality consistency, better shelf-life, and improved safety against roof falls.

2️⃣ Resin Capsule – Composition

A resin capsule consists of:

Outer polyester film
Two-component system inside:
- Resin (polyester/epoxy)
- Catalyst/Hardener (benzoyl peroxide)

On rotation of the bolt, both components mix and polymerize, forming a solid high-strength grout.

3️⃣ Revised DGMS Standards (Key Points)

1. Capsule Dimensions & Packaging: Diameter must match the hole diameter (32 mm, 27 mm, etc.). Length as per bolt requirement (250 mm, 400 mm, 600 mm). Package must be clearly labelled with Manufacturer, Batch number, Expiry date, and Strength rating.

2. Physical & Chemical Testing Requirements:

Viscosity & Gel Time: Must comply with IS/ISO standards. Gel time limits: Fast-set (10–20 sec), Slow-set (1–3 min).
Compressive Strength: Test cubes must meet minimum compressive strength at 1 hour and 24 hours.
Shelf-Life Test: Must retain strength up to 12 months. Temperature-controlled storage required.

3. Pull-Out Test (Load Test): Each batch must undergo Pull-Out Testing. Minimum pull load should meet DGMS requirement (typically ≥ 10 tonnes). Recommended frequency: Monthly, After receipt of new batch, Post-long storage.

4️⃣ Installation Standards

Hole Drilling: Diameter as per bolt + capsule size; Smooth hole (no over-drilling); Hole must be clean & dry.

Bolt Installation: Insert resin capsule → Push bolt to end → Rotate bolt to mix resin → Hold until setting time → Torque the nut after curing.

5️⃣ Storage & Handling Standards

Store below 25°C.
Keep capsules away from sunlight.
Avoid mechanical damage.
FIFO (First In First Out) rule.

6️⃣ Advantages of Resin Capsules

Rapid setting → immediate roof support
Suitable for wet & dry strata
Higher bond strength than cement grouts
No shrinkage
Long-term stability

7️⃣ Common Failures

Improper mixing, damaged capsules, expired capsules, water-filled holes, incorrect hole diameter, or wrong rotation speed.

⚡ QUICK ONE-LINERS (Revision Points)

Resin capsules contain resin + catalyst.
Gel time defines setting speed.
Pull-out test checks anchorage strength.
Capsules must be batch-marked with expiry.
DGMS requires resin testing before use.
Wet holes reduce bonding strength.
Shelf-life: usually 12 months.
Bolt rotation mixes resin & hardener.
Pull-test load should meet DGMS norms.
Storage temperature must be controlled.

🧠 DESCRIPTIVE MODEL Q&A

Q. Explain the revised DGMS standards for testing and use of resin capsules in roof bolting.

Answer:
DGMS mandates that resin capsules used for roof bolting must be tested for gel time, compressive strength, viscosity, and shelf-life as per approved IS/ISO standards. Each batch must undergo pull-out tests to verify anchorage strength. Capsules must be stored properly, labelled with batch details, and used before expiry. The hole must be drilled to correct dimensions, and resin must be properly mixed by bolt rotation to achieve full strength. These standards ensure safe and reliable roof support in underground mines.

🧮 25 MCQs

Q1. Resin capsules are used for:

Solution: Resin capsules are the bonding agent used to anchor roof bolts into the rock strata.

Q2. Resin capsule contains:

Solution: The two main components that react to harden are the resin and the catalyst (hardener).

Q3. Gel time indicates:

Solution: Gel time is the time it takes for the mixed resin to begin hardening or setting.

Q4. Pull-out test checks:

Solution: The pull-out test measures the force required to pull the bolt out, verifying the strength of the resin bond.

Q5. Fast-set resin typically sets in:

Solution: Fast-set resins are designed for rapid curing to provide immediate support.

Q6. Resin capsules must be stored below:

Solution: High temperatures can degrade the resin or cause premature hardening, so cool storage is essential.

Q7. Expired resin capsules:

Solution: Expired capsules may not cure properly, leading to weak support and potential roof falls.

Q8. Hole must be:

Solution: A clean and dry hole ensures optimal bonding between the resin, bolt, and rock.

Q9. Label must include:

Solution: Batch numbers allow for traceability and quality control tracking.

Q10. Resin capsule outer layer is:

Solution: A thin polyester film contains the chemicals and shreds easily during installation to allow mixing.

Q11. Mixing occurs when bolt is:

Solution: Rotation of the bolt shreds the capsule and mixes the resin and catalyst components.

Q12. Strength test done at:

Solution: Testing at these intervals verifies both early strength gain and final cured strength.

Q13. Shelf-life of resin capsules:

Solution: Under proper storage conditions, standard resin capsules typically last for about a year.

Q14. Pull-test frequency:

Solution: Regular monthly testing ensures ongoing quality control of the support system.

Q15. Resin bonding is affected by:

Solution: Water in the drill hole can dilute the resin or interfere with the bond interface, reducing strength.

Q16. DGMS tests resin capsules for:

Solution: Strength (compressive and bond) is the critical safety parameter tested.

Q17. Resin used for:

Solution: Resin capsules are a key component of active roof support systems.

Q18. Resin-hardeners are:

Solution: Benzoyl peroxide is the standard chemical catalyst used to initiate the hardening reaction.

Q19. Over-drilling leads to:

Solution: If the hole is too large, the resin may not fill the annulus completely, resulting in poor anchorage.

Q20. Capsules must be:

Solution: Physical damage can cause premature mixing or leakage, ruining the capsule.

Q21. Main purpose of resin capsule:

Solution: Its sole purpose is to bond the roof bolt securely to the rock mass.

Q22. Resin testing follows:

Solution: Testing protocols are defined by relevant Indian (IS) or International (ISO) standards.

Q23. Capsule diameter depends on:

Solution: The capsule must fit the drill hole with a small annulus to ensure proper mixing and bonding.

Q24. FIFO ensures:

Solution: First In, First Out ensures older stock is used before it expires, minimizing waste. (Correction: Ideally "Oldest stock used first", but in context of freshness, FIFO manages inventory age).

Q25. Resin capsule failure may cause:

Solution: If the resin fails to bond, the roof support fails, leading to potential roof collapse.

🔗 INTERNAL LINKING SUGGESTIONS

Related Topic	Read More On...
Roof Bolting	Roof Bolt Support System Notes
Strata Control	Strata Monitoring in Longwall Workings
DGMS Circulars	DGMS Tech Circulars
Support Rules	CMR 2017 Part 2 - Working & Supervision Rules

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