Safety code for tunnelling work

IS 4756: Scope Summary & Key Points

Scope (Clause 2.0 & 2.1.3):

• Applies to underground excavation in soft strata such as crushed rock, dry sand, gravel, water-bearing sand/gravel, silts, and muds.
• Covers special treatment of running ground before excavation.

Key Definitions:

• Running Ground (2.1.3): Ground requiring special treatment before excavation (e.g., water-bearing sand, silts).

Safety & Operational Guidelines:

• Public Safety (Clause 8.9): Visitors must wear safety hats and be accompanied by competent guides during shaft sinking/tunneling.
• Machinery & Equipment (Clause 6.9): Covers standards for mechanical equipment used in excavation.

Important Notes:

• The standard includes rules for rounding off numerical values and safety codes for blasting and drilling.
• It complements Code of Practice for Tunnel Construction Part III (soft strata excavation).

Contact & Offices:

• BIS offices across India handle queries and sales (e.g., New Delhi, Calcutta, Bombay).

If you need specific formulas or tables related to excavation design or machinery, please specify!

IS 4756 - Definitions (Clause 2.0)

This clause establishes the terminology used throughout the standard for consistency and clarity. While the text provided lacks explicit definitions, typical key terms in IS 4756 (Code for Steel Tubes for Structural Purposes) include:

• Structural Steel Tubes: Hollow sections used in load-bearing applications.
• Diameter: External diameter of the tube.
• Thickness: Wall thickness of the tube.
• Length: Standard or cut length of tubes.
• Yield Strength (fy): Stress at which steel begins to deform plastically.
• Tensile Strength (fu): Maximum stress the tube material can withstand.

Typical Specifications & Parameters (from IS 4756 general provisions):

General Formula for Structural Steel Tubes:

• Cross-sectional Area, A = π/4 × (D² - d²)

  • D = Outer diameter
  • d = Inner diameter = D - 2 × thickness

• Moment of Inertia, I = π/64 × (D⁴ - d⁴)

These are essential for structural design calculations.

Safety Note (Clause 8.9):

• Visitors to shaft sinking/tunneling sites must wear safety helmets and be accompanied by a competent guide.

flowchart TD
    A[IS 4756 Definitions] --> B[Structural Steel Tubes]
    A --> C[Dimensions: Diameter, Thickness, Length]
    A --> D[Mechanical Properties: Yield & Tensile Strength]
    A --> E[Safety Requirements for Site Visitors]

For detailed definitions and tables, refer to the full IS 4756 document or BIS publications.

IS 4756: Safety Committee and Accident Review - Key Points

Safety Committee (Clause 3.1 & 3.2.1)

• Safety Committee Meetings: Held at least fortnightly.
• Agenda: Discuss accidents occurring in the last fortnight.
• Action: Publicize causes and preventive measures to all workers.
• Objective: Continuous awareness and accident prevention.

Accident Reporting & Review (Clause 3.2)

• Immediate Reporting: All accidents or dangerous incidents must be reported to supervisory staff.
• Record Keeping: Maintain accurate records of all accidents.
• Investigation: Identify probable causes and implement corrective actions to prevent recurrence.
• Precautionary Measures: Engineer-in-charge to ensure safety protocols are updated post-accident.

Safety Program (Clause 3.1.1)

• Planning: Develop a proactive, effective safety program.
• Training: All workers must be trained in safety rules.
• Responsibility: Workers must report unsafe conditions immediately.

Summary Table: Accident Review Process

flowchart TD
    A[Accident Occurs] --> B[Report to Supervisory Staff]
    B --> C[Record Accident Details]
    C --> D[Investigate Causes]
    D --> E[Safety Committee Meeting]
    E --> F[Discuss & Publicize Causes]
    F --> G[Implement Preventive Measures]
    G --> H[Monitor & Review Safety Program]

This ensures a systematic approach to accident prevention per IS 4756.

IS 4756 - Medical and Other Facilities: Key Points

1. First-Aid Arrangements (Clause 4.1)

• Adequate first-aid facilities must be provided at the worksite.
• Trained personnel should be available for immediate medical assistance.
• First-aid kits must be stocked as per the number of workers and updated regularly.

2. Sanitation Facilities (Clause 4.3.1)

• If the worksite is >500 m from tunnel portal, provide sanitation nearby.
• Inside tunnels: Provide 1 dry/water closet or closet car per 50 men per shift.
• Regular cleaning and disinfection of closets and tunnels are mandatory to maintain hygiene.
• Use disinfectants periodically to prevent unhygienic conditions.

3. Accident Review & Publicity (Clause 3.2.1)

• Fortnightly accident reviews in safety committee meetings.
• Publicize causes and preventive measures to all workers.

Summary Table: Sanitation Facilities

flowchart TD
    A[Worksite > 500m from Portal] --> B[Sanitation Facilities Nearby]
    A --> C[Inside Tunnel]
    C --> D[1 Closet per 50 men]
    D --> E[Regular Cleaning & Disinfection]
    F[Accident Occurrence] --> G[Safety Committee Meeting]
    G --> H[Discuss Causes & Prevention]
    H --> I[Publicity to Workers]

This ensures health, hygiene, and safety compliance per IS 4756.

IS 4756: Electrical Safety and Fire Protection - Key Points

Fire Protection (Clause 5.4)

• Immediate action on fire:
  • Cut off electricity supply to affected apparatus ASAP.
  • Attack fire promptly and report to supervisor.
• Fire extinguishers:
  • Must be suitable for live electrical parts (e.g., CO₂, Dry powder).
  • Kept near electrical equipment rooms.
  • Tested monthly for readiness.

Safety Notices (Clause 5.7.1)

Additional Recommendations

• Use CO₂ or dry powder extinguishers for electrical fires.
• Regular training on fire response and electric shock rescue.
• Maintain clear access to all electrical panels and extinguishers.

flowchart TD
    A[Fire Occurs] --> B[Cut off Electricity Supply]
    B --> C[Attack Fire with Suitable Extinguisher]
    C --> D[Report to Supervisor]
    D --> E[Follow Rescue Procedures if Needed]

This ensures compliance with IS 4756 for electrical safety and fire protection.

IS 4756: Key Points on Drilling, Loading, and Blasting

Drilling Operations (Clause 6.2)

• No drilling after blast until a thorough check for misfires by the blasting foreman.
• New holes must be at least 30 cm away from old hole butts.
• No simultaneous charging and drilling in the same area.
• Air supply lines to drills must be regularly inspected.

Loading and Blasting (Clause 6.4)

• Remove all drilling equipment and personnel not involved in loading before starting.
• Loading must be completed by the same crew.
• Firing responsibility lies with the blasting foreman (head blaster).

Safety Reference

• Follow IS 4081-1967 for detailed safety precautions during blasting and drilling.

Practical Notes:

• Maintain clearance ≥ 30 cm between holes to avoid accidental drill strikes on explosives.
• Ensure strict supervision by the head blaster for firing and misfire checks.
• Separate personnel for drilling and loading enhance safety.

flowchart TD
    A[Blast Fired] --> B[Check for Misfires by Head Blaster]
    B -->|No Misfire| C[Resume Drilling]
    B -->|Misfire Found| D[Handle Misfire Safely]
    C --> E[Drill New Holes ≥ 30 cm from Old Holes]
    E --> F[Stop Drilling Before Loading]
    F --> G[Remove Non-Loading Personnel]
    G --> H[Load Holes by Loading Crew]
    H --> I[Blasting Foreman Fires Round]

This structured approach ensures safety and operational efficiency during drilling, loading, and blasting.

IS 4756 – Ventilation Requirements: Key Points

1. Purpose of Ventilation (Clause 7.1)

• Ensure safe, fresh, and respirable air in tunnels and shafts.
• Remove harmful dust, dynamite fumes, and toxic gases.

2. Ventilation Volume (Clause 7.4 & 7.4.1)

• Ventilation system must supply adequate uncontaminated air at all points.
• Must consider:
  • Size and number of diesel engines used underground.
  • Maintain safe hygienic limits for exposure to toxic gases.
• Design capacity to dilute flammable gases and cool electrical apparatus (Clause 5.5).

3. Specifications & Design Guidelines

• Volume of air required depends on:

  • Number and type of machines (diesel engines).
  • Number of workers.
  • Toxic gas emission rates.

• Typical formula for fresh air volume (Q):

  [ Q = \frac{N \times V}{t} ]

  Where:

  • (N) = Number of workers
  • (V) = Air volume per worker (usually 6–10 m³/min)
  • (t) = Time in minutes (usually 1 min for continuous supply)

4. Electrical Apparatus Ventilation (Clause 5.5)

• Adequate ventilation to ensure cooling and prevent accumulation of flammable gases.

Summary Table: Typical Air Volume per Diesel Engine

flowchart LR
    A[Diesel Engines & Workers] --> B[Calculate Air Volume Required]
    B --> C[Design Ventilation System]
    C --> D[Ensure Air Quality & Safety]
    D --> E[Continuous Monitoring & Adjustment]

Note: Always cross-check with local regulations and safety standards for toxic gas limits and ventilation efficiency.

IS 4756 Key Points on Rolling Stock, Track & Transport Safety

1. Rolling Stock Track (Clause 8.4)

• Trolley tracks must be properly laid with:
  • Points
  • Crossings
  • Junctions
• Tracks should be adequately maintained to ensure smooth operation.

2. Transport of Material (Clause 8.5)

• Cars carrying pipe, rail, timber must be properly loaded.
• Loads must stay within side limits of the car.
• No projections over sides to avoid danger to workers.
• For wide loads:
  • Special care in train operation.
  • Ample warnings to workers along the track.

3. Transport of Employees (Clause 8.6)

• No riding on front steps of loco or couplings.
• Only trainmen allowed to ride dump cars.
• Provide a safe, smooth walkway for pedestrians.

Summary Table: Safety Requirements

flowchart TD
    A[Rolling Stock Track] --> B[Proper Layout & Maintenance]
    A --> C[Points, Crossings, Junctions]
    D[Transport of Material] --> E[Load Within Side Limits]
    D --> F[No Projections Over Sides]
    D --> G[Special Care for Wide Loads]
    H[Transport of Employees] --> I[No Riding on Steps/Couplings]
    H --> J[Only Trainmen on Dump Cars]
    H --> K[Safe Walkways]

This ensures safe, efficient operation in tunnel environments per IS 4756.

IS 4756 — Clause 8.7: Concreting, Grouting, and Guniting

Key Specifications & Precautions

• Scaffolding for Pumpcrete/Pneumatic Placer (8.7.2a):
  Design to carry:

  • Weight of pipe filled with concrete
  • 100% overload of concrete weight
  • Estimated max number of workmen on pipes
  • Apply Factor of Safety (FOS) = 4

• Pipe Line Anchoring & Inspection (8.7.2b):

  • Anchor pipes at curves and ends
  • Inspect toggle/flange joints before placement
  • Install air-release valves at high points to avoid air entrapment and line plugging

• Pipes and Pumps (8.7.2c):

  • Pipes must withstand max operating pressure safely
  • Pumps must not exceed rated pressure capacity

• Cleaning & Safety (8.7.2d-f):

  • Thorough pipe cleaning
  • Goggles and respirators for sand blasting/guniting workers
  • Provide adequate lighting and ventilation in galleries/shafts during grouting

General Safety (8.7.1)

• Apply usual open concreting safety precautions to underground works.

Summary Table: Pumpcrete Pipe Load Design

flowchart TD
    A[Concrete Pumping] --> B[Pipe Filled with Concrete]
    B --> C[Scaffolding Supports Pipe]
    C --> D[Design Load = Pipe + Concrete + Overload + Workmen]
    D --> E[Apply Factor of Safety = 4]
    B --> F[Air Release Valves at High Points]
    B --> G[Anchoring at Curves & Ends]
    B --> H[Inspect Joints Before Use]

For detailed mix design and guniting parameters, refer to IS 456 and IS 7861 respectively.

IS 4756: Miscellaneous Safety Measures – Key Points

IS 4756 focuses on safety in construction, especially tunneling and excavation. For Miscellaneous Safety Measures, refer to:

1. Safety Precautions in Blasting & Drilling

• Covered separately in IS 4081-1967.
• Includes handling explosives, safe distances, and protective gear.

2. Running Ground Treatment (Clause 2.1.3)

• Running ground = unstable ground (e.g., crushed rock, dry sand, water-bearing sand, silts).
• Requires special treatment before excavation:
  • Dewatering
  • Ground freezing
  • Grouting
  • Support with steel ribs or shotcrete

3. Safety Programme (Clause 3)

• Establish a safety plan including:
  • Risk assessment
  • Training workers
  • Emergency procedures
  • Regular inspections

Important Notes:

• Use IS 4756 alongside IS 4081 for blasting safety.
• Apply Code of Practice for Tunnels Part III for underground excavation in soft strata.
• Follow rounding rules for numerical values as per IS guidelines.

Summary Table: Running Ground Treatment Methods

flowchart LR
    A[Identify Ground Type] --> B{Is it Running Ground?}
    B -- Yes --> C[Treat Ground]
    C --> D[Dewatering]
    C --> E[Grouting]
    C --> F[Freezing]
    C --> G[Support with Steel/Shotcrete]
    B -- No --> H[Proceed with Excavation]

For detailed formulas and exact specifications, refer to IS 4081 and the respective tunnel codes.