Code of Practice for Laying of Concrete Pipes

IS 783 Scope & Key Specifications Summary

Scope (Clause 3.0 & 4.1)

• Applies to concrete pipes (with/without reinforcement).
• Defines symbols and coefficients for load calculations on pipes under various trench and embankment conditions.

Key Symbols & Definitions (Clause 4.1)

Load Factors (Examples from Clauses 12.3 & 13.3)

• Load factors F depend on projection ratio (p), depth ratio (H/D), and trench width (B).
• For Type B Bedding - Rock Foundation (Clause 12.3):

• For Type C Bedding - Rock Foundation (Clause 13.3):

| H/D | Fe (p=0.9, +1.0) | Fe (p=0.9, -1.0) | |------|------------------

IS 783: Types of Loading - Key Formulas & Tables

1. Minimum Test Load (Clause 5.1)

• Reinforced Pipe:
  [ \text{Minimum Test Load} = \sum \frac{\text{Vertical Loads}}{\text{Load Factor (from Clause 10)}} ]
• Unreinforced Pipe:
  [ \text{Minimum Test Load} = 1.5 \times \left(\sum \frac{\text{Vertical Loads}}{\text{Load Factor}}\right) ]

2. Vertical Loads on Pipes (Clause 6.1)

• Static load due to fill material
• Static load due to superimposed loads on fill
• Internal static load from water weight inside pipe

3. Impact Factors for Railway Loading (Clause 11.4)

Interpolate linearly for intermediate depths.

4. Load Factors (F) for Bedding Types (Clause 12.3)

5. Coefficients for Load Calculations (Figures 1-5)

• (C_e, C_a, C_p, C_t, C_u) are coefficients depending on soil type & trench conditions.
• Used in formulas like:
  [ W_e = C_e w D^a, \quad W_i = C_t w

Key Formulas & Specifications for Materials (IS 783 referencing IS 458)

1. Crack Load for Pipes (Clause 119.6):

• For a 1600 mm diameter pipe, the 0.25 mm crack load = 119.6 kN/m (from IS 458:2003 Tables 6, 7, 8).
• Applies to reinforced/unreinforced precast concrete pipes.

2. Pipe Dimensions (Example 8b):

• Internal diameter, ( d = 900 , mm )
• Wall thickness, ( t ) (given or calculated)
• External diameter, ( D = d + 2t = 1000 , mm )
• Trench width, ( B = D + 300 = 1300 , mm )
• Trench depth = 3 m

3. Data Required for Load Assessment (Clause 6.2):

• Height of fill above pipe, ( H )
• Unit weight of fill material, ( w )
• Load nature (distributed/concentrated, static/dynamic)
• Installation conditions, friction coefficients, settlement ratio, etc.

4. Vertical Load on Pipe (Clause 11.3, Table B-11):

• Load factor ( F ) depends on fill height ( H ), bedding type, trench width, and foundation type (Type B bedding - earth or rock).
• Example values for ( p=0.7 ) and ( p=0.5 ) (load factors vary with ( H )):

Summary Table

IS 783: Bedding and Foundation Conditions — Key Load Factor Tables

The code provides load factor F values for different bedding types (A, B, C) and foundation conditions (rock, earth) under positive projection, wide trench, and imperfect trench scenarios.

Load Factor F Tables Summary

Typical Load Factor F Values (Excerpt)

Usage Notes

• p: Projection parameter (ratio related to trench width or footing dimension).
• H, B: Depth or width parameters related to trench or footing.
• +1.0 / -1.0: Positive or negative projection condition effects.
• Use these load factors to multiply applied loads for safe design against trench and foundation instability.

Conceptual Diagram of Bedding Types and Conditions

flowchart TD
    A[Trench Condition] --> B{Bedding Type}
    B --> B1[Type A - Rock]
    B --> B2[Type B - Rock]
    B --> B3[Type B - Earth]
    B --> B

IS 783: Load Factors and Load Calculations

Key Points from IS 783:

• Load Factor (Ft) is used to calculate the required test load on pipes.
• It varies depending on:
  • Type of load (dead, live, test loads)
  • Installation conditions (buried, open, supported)

Typical Load Factors (Ft) from Clauses 3.4, 5.3, 6.3 (as per IS 783):

Note: Exact values depend on detailed conditions in Clause 10 (installation specifics).

Load Calculation Formula:

[ \text{Required Test Load} = \text{Working Load} \times F_t ]

Where:

• Working Load = actual load expected in service (dead + live loads)
• Ft = Load factor from IS 783

Summary:

• Use Ft from IS 783 based on pipe type & installation.
• Multiply working load by Ft to get test load.
• Refer Clause 10 for detailed installation conditions affecting Ft.

flowchart LR
    A[Working Load] --> B[Multiply by Ft]
    B --> C[Required Test Load]
    C --> D[Pipe Testing]

This ensures safety and reliability in pipe load testing per IS 783.

IS 783 - Jointing of Pipes: Key Formulas, Tables & Specifications

1. General Jointing Requirements (Clause 15.4.2)

• Cleanliness of joint surfaces.
• Correct component location & centralization of spigot inside socket.
• Correct gap between spigot end and socket back (for rubber ring joints).
• Use approved lubricants.
• Follow manufacturer recommendations.

2. Types of Joints

3. Load Interaction Formula (Clause 13.1)

Relationship between internal pressure and external load:

[ W = \text{site external working load (kN/m)}, \quad F = \text{load factor} ]

[ T = \text{external 3-edge bearing load per m pipe}, \quad P_t = \text{hydrostatic test pressure (MPa)} ]

[ P = \text{working pressure on line (MPa)}, \quad W_F = \frac{W}{F} = \text{test load equivalent} ]

• For safe design: ( P \times W_F ) must lie below the IS 783 curve (Fig. 6).
• If above curve → increase test load ( T ) or test pressure ( P_t ).

4. Summary Diagram of Joint Types

graph TD
    A[Pipe Sections] --> B(Socket & Spigot Joint)
    A --> C(Internal Flush Joint)
    B --> D[Cement Mortar (1:2) filling annular gap]
    C --> E[1-3 cm internal joint space]
    E --> F[Cement mortar filling, flush inside/outside]

Handling and Stacking of Pipes (IS 783)

Stacking (Clause 15.1.3):

• Pipes may be stacked directly on level, rock-free ground.
• When stacking in tiers, timber bearers must be placed between tiers.
• Maximum recommended stacking height: 2 tiers.
• For more than 2 tiers, consult the manufacturer.

Transport (Clause 15.1.1):

• Pipes must be securely loaded on vehicles to prevent movement during transit or transfer.

Key Formulas for Vertical Loads (Clauses 7, 8, 9)

• Vertical load on pipes depends on installation and backfill conditions.
• Use coefficients from Figures 1 to 5 for embankment/trench conditions (e.g., Ce, Ca, Cp, Ct, Cu).
• General formula for vertical load ( W_e ) in embankment:

[ W_e = C_e \times W \times D^a ]

Where:

• ( C_e ) = coefficient (from Fig. 1)
• ( W ) = unit weight of fill
• ( D ) = depth of cover
• ( a ) = exponent (usually 1 or 2 depending on condition)

Minimum Test Load (Clause 5.1)

• Reinforced Pipes:

[ \text{Test Load} = \sum \left(\frac{\text{Calculated Load}}{\text{Load Factor}}\right) ]

• Unreinforced Pipes:

[ \text{Test Load} = 1.5 \times \left[\sum \left(\frac{\text{Calculated Load}}{\text{Load Factor}}\right)\right] ]

Summary Table: Stacking & Handling

flowchart TD
    A[Pipe Stacking] --> B{Ground Condition}
    B -->|Level & Rock-free| C[Stack directly]
    B -->|Uneven or rocky| D[Use timber bearers]
    C --> E{Number of tiers}

IS 783: Laying Procedures - Key Points & Tables

1. Laying and Jointing (Clause 15.4.1)

• Use proper lifting tackle (shear slings, chain blocks, cranes).
• Lay pipes preferably upgrade on slopes.
• For rubber ring joints, spigot is easier to insert.
• For collar joints, slip collars before laying next pipe.
• Expansion joints:
  • Buried pipes: max 100 m spacing.
  • Exposed pipes: max 45 m spacing.
• Use cast iron/steel collars & lead caulking per IS 782-1978 for expansion joints.
• Rubber ring joints may omit expansion joints.
• Close open pipe ends when not laying to prevent buoyancy and movement.

2. Anchoring on Steep Gradients (Clause 15.4.3)

• For gradients > 1:15, use spacers to maintain correct spigot-socket gap.
• Firmly restrain last pipe after jointing until backfilling and compaction.

3. Bedding Considerations

• Steep gradients may cause water flow in trench, disturbing bedding.
• Use alternative bedding or clay water stops if water flow is substantial.

Summary Diagram: Laying & Anchoring on Slopes

flowchart TD
    A[Lifting Pipes] --> B{Joint Type}
    B -->|Rubber Ring| C[Spigot into Socket]
    B -->|Collar Joint| D[Slip Collar Before Next Pipe]
    C & D --> E[Lay Pipes Upgrade on Slope]
    E --> F{Gradient Steeper than 1:6?}
    F -->|Yes| G[Provide Transverse Anchors]
    F -->|No| H[Anchors Usually Not Required]
    G --> I[Use Table 3 for Spacing]

IS 783: Testing and Site Test Pressure - Key Points & Formulas

1. Site Test Pressure (Clause 15.5.2):

• Minimum test pressure = Maximum operating pressure + Surge pressure allowance
• Maximum test pressure ≤ Works hydrostatic proof test pressure
• If pressure measured above lowest point, add static head allowance:

[ P_{lowest} = P_{measured} + \rho g h ]

where
( \rho ) = density of water,
( g ) = acceleration due to gravity,
( h ) = height difference.

2. Hydrostatic Test Procedure (Clause 15.5.1 & 15.5.3):

• Fill pipeline with water, remove air via vents/swab.
• Maintain test pressure for absorption stabilization.
• Use calibrated container to measure water loss.
• Acceptance criteria for non-absorbent pipes (steel/iron):

[ \text{Water loss} \leq 0.1 , \text{litres} \times \frac{\text{pipe diameter (mm)}}{1000 , \text{m}} \times \frac{\text{per day}}{30 , \text{m head}} ]

• For concrete pipes, absorption/permeability depend on:
  • Density, water-cement ratio, thickness, pressure, duration.

3. Anchoring (Clause 15.5.3):

• Calculate thrust on stop ends using full socket internal diameter.
• Design anchors to resist thrust.
• Concrete anchor blocks often used for stability.

Summary Table: Test Pressure Limits

flowchart TD
    A[Start: Pipeline Filled with Water] --> B[Remove Air via Vents/Swab]
    B --> C[Apply Test Pressure (≥ Operating + Surge)]
    C --> D[Maintain Pressure for Absorption]
    D --> E

IS 783: Repair and Inspection of Precast Concrete Pipes

Key Points from Clause 15.3 (Pipe Inspection and Repairs):

• Pipes should be inspected regularly for cracks, spalling, and other damages.
• Repair methods must ensure restored structural integrity and durability.
• Use appropriate patching materials compatible with concrete.

Crack Load & Ultimate Load Reference (IS 458:2003 Tables):

• Crack load = load causing 0.25 mm crack width.
• Ultimate load = maximum load pipe can carry.

Inspection & Repair Summary:

• Use IS 458:2003 for updated load tables.
• Repair cracks < 0.25 mm by filling with cementitious grout.
• For larger cracks or damaged pipes, replacement or reinforcement is recommended.
• Refer to Amendment No. 2 to IS 783:1985 for latest specifications and examples.

flowchart TD
    A[Inspection] --> B{Crack Width < 0.25 mm?}
    B -- Yes --> C[Fill with Cementitious Grout]
    B -- No --> D{Structural Integrity?}
    D -- Good --> E[Reinforce & Repair]
    D -- Poor --> F[Replace Pipe]

References: IS 783:1985 Clause 15.3, IS 458:2003 Tables 2,3,4,5,6,7,8.

IS 783: Special Installation Conditions - Key Points

1. Specials for Water Mains, Sewer Lines, Irrigation Works (Clause 15.4.4)

• Specials (curves, bends, branches, manholes, air valves, blow-offs) must comply with:
  • IS 784: 2001 (Prestressed Concrete Pipes and Specials)
  • IS 7322: 1985 (Steel Cylinder Reinforced Concrete Pipes Specials)
• Length of specials varies per site; concrete pipes have standard lengths.

2. Load Factors for Installation Conditions (Clause 15.3 & Appendix B)

• Load factor F depends on trench condition, bedding type, and soil foundation.
• Use the lesser load from trench or positive projection conditions for test load.

3. Load Factor Tables for Different Bedding Types

(Refer to tables B-14, B-15, B-16 in IS 783 for detailed values)

4. Installation Conditions Covered

• Wide trench condition
• Positive projection condition
• Imperfect trench condition

Summary Diagram: Installation Conditions & Load Factor Selection

flowchart TD
    A[Pipe Installation] --> B{Trench Condition?}
    B -->|Ordinary Trench| C[Calculate Load: Trench Condition]
    B -->|Wide Trench / Positive Projection| D[Calculate Load: Positive Projection]
    C --> E[Select Lesser Load]
    D --> E
    E --> F[Apply Load Factor F (from IS 783 tables)]
    F --> G[Determine Test Load]

References:

• IS 784: 2001 (Prestressed Concrete Pipes)
• IS 7322: 1985 (Steel Cylinder Reinforced Concrete Pipes)
• IS 783: Clause 15.3, 15.4.4, Appendix B tables for load

Key Formulas and Specifications for Load Calculation on Pipes (IS 783, Appendix A & C):

1. Pipe Dimensions:

• Internal diameter, ( d = 900 , mm )
• Wall thickness, ( t )
• External diameter, ( D = d + 2t = 1000 , mm )
• Trench width, ( B = D + 300 = 1300 , mm )
• Trench depth to pipe invert, ( H = 3 , m )

2. Vertical Load on Pipe (Trench Condition):

The vertical load ( W_c ) on the pipe due to fill material is reduced by friction between fill and trench sides.

• Load factor formula:

[ l = 1.15H + 2D + S ]

Where:

• ( H ) = depth of fill above pipe invert

• ( D ) = external pipe diameter

• ( S ) = width of trench side clearance (assumed)

• Calculate parameters:

[ \frac{l}{2H} \quad \text{and} \quad \frac{D}{2H} ]

Use these to find load reduction factor ( C_p ) from Fig. 3 (IS 783).

• Then,

[ W_c = C_p \times \gamma \times H \times B ]

Where:

• ( \gamma ) = unit weight of fill material (e.g., wet clay)
• ( B ) = trench width

3. Crack Load from IS 458:2003 (for reinforced concrete pipes):

• For 1600 mm dia pipe, 0.25 mm crack load = 119.6 kN/m

4. Reference Tables:

• Tables 6, 7, 8 of IS 458:2003 provide crack and ultimate loads for various pipe diameters and reinforcement classes.

Summary Table (Example):

IS 783: Safety & Quality Control for Concrete Pipes

Key Formulas (Load Calculations)

• Vertical Load from Fill Material:

  [ V = C \times \gamma \times H \times B ]

  Where:

  • (C, C_n, C_p, C_t, C_u) = load coefficients (see Fig. 1-5 in IS 783)
  • (\gamma) = unit weight of fill material
  • (H) = depth of fill over pipe (m)
  • (B) = trench width at pipe top (m)

• Projection Ratio:

  [ p = \frac{h}{D} ]

  Where:

  • (h) = vertical distance from pipe top to undisturbed ground (m)
  • (D) = external pipe diameter (m)

• Horizontal Pressure Ratio (Rankine's formula):

  [ K = \frac{1 - \sin \phi}{1 + \sin \phi} ]

  Where (\phi) = angle of internal friction of fill material.

Important Symbols (Clause 4.1)

• (d), (D): Internal & external pipe diameters (m)
• (P): Concentrated load (kN)
• (F_e, F_p, F_t): Load factors depending on installation conditions
• (h, h', H): Depths related to pipe installation and fill

Quality Control & Testing

• Cracking load values from IS 458 tables (e.g., 0.25 mm crack load for 1600 mm pipe = 119.6 kN/m).
• Pipes tested for cracking load, ultimate load as per IS 458 and IS 783 revisions.
• Rounding off test results as per IS 2-1960.

Reference Tables

Notes

• Load coefficients depend on installation: trench, embankment (positive/negative projection), imperfect trench

IS 783: References & Related Standards - Key Points & Formulas

Referenced Standards:

• Concrete Pipes: Specification for concrete pipes (with/without reinforcement) – 2nd revision.
• Prestressed Concrete Pipes: Specification including fittings – 1st revision.
• Testing Methods: Methods of test for concrete pipes – 1st revision.
• Fittings & Specials: IS 784:2001, IS 7322:1985 for specials like bends, branches, manholes.
• Rounding Off: As per IS 2:1960 for test/analysis results.

Important Symbols & Coefficients (Clause 4.1)

Load Calculation Concept (Summary)

• Vertical load on pipe = weight of fill + superimposed loads.
• Use coefficients (C, Cn, Cp, Ct, Cu) depending on installation conditions.
• Load factors (Fe, Fp, Ft) adjust the computed loads.
• Crack load/ultimate load values referenced from IS 458:2003 tables (e.g., 119.6 kN/m for 1600 mm pipe).

Example: Rankine's Active Earth Pressure Coefficient

[ K = \frac{1 - \sin \phi}{1 + \sin \phi} ]

where (\phi) = angle of internal friction of soil.

IS 783 Amendments & Updates - Key Points

• Crack Load Values Update:
  Replace old crack load references from IS 458:1971 with updated values from IS 458:2003 (Tables 6, 7, 8).

  • Example: For 1600 mm dia pipe, 0.25 mm crack load = 119.6 kN/m (IS 458:2003) replaces old 1971 value.

• Specification References:
  Updated footnotes specify:

  • Specification for precast concrete pipes (with/without reinforcements) (4th revision)
  • Prestressed concrete pipes and fittings (1st & 2nd revisions)
  • Specials per IS 784:2001 and IS 7322:1985.

• Rounding Off Values:
  Final test/analysis values to be rounded per IS 2:1960, maintaining significant figures as per specified values.

• Suitability Criteria:
  Use updated crack load tables to select pipe classes (e.g., NP3 class pipe with 0.25 mm crack load ≥ 15.5 kN/m suitable for 300 mm dia).

• Specials & Fittings:
  Length and type per IS 784:2001 & IS 7322:1985, varies with site conditions.

Summary Table: Crack Load Reference Update

flowchart LR
    A[Old Crack Load Data] --> B[IS 458:1971]
    B -->|Superseded| C[IS 458:2003 Tables 6,7,8]
    C --> D[Updated Crack Load Values]
    D --> E[Pipe Selection per Updated Values]
    E --> F[Compliance with IS 783 Amendments]

**Use IS