Code of practice for design and construction of port and harbour structures, Part 6: Block work

IS 9527 Part 6 — Scope: Key Formulas, Symbols & Specifications

1. Scope Summary

• Applies to design and construction of port and harbour structures.
• Design parameters must be based on detailed site investigations and lab tests (Clause 10.2.1).
• Uses symbols defined in Clause 4.1 for consistent design notation.

2. Key Symbols (Clause 4.1)

3. Design Parameters

• Must be derived from site-specific investigations and testing.
• Refer to IS 4651 Parts 1-4 for detailed guidance on site investigation, earth pressures, loading, and general design.

4. Related IS Codes

• IS 456: Plain and Reinforced Concrete
• IS 4651 (Parts 1-4): Ports and Harbours design
• IS 2809: Soil Engineering Glossary
• IS 7314: Port and Harbour Engineering Glossary

Typical Formula for Active Earth Pressure Coefficient (KA)

[ K_A = \tan^2 \left( 45^\circ - \frac{\phi}{2} \right) ]

Where,

• ( \phi ) = angle of internal friction of soil

Conceptual Diagram: Forces on a Retaining Wall

IS 9527 Part 6: Definitions & Terminology (Key Symbols & Parameters)

• Letter Symbols:

• Design Basis:
  • Parameters must be derived from detailed site investigations and laboratory tests (Clause 10.2.1).
  • Load calculations follow Clauses 9.2.1 to 9.2.7.

Typical Formula for Active Earth Pressure Coefficient (KA)

For cohesionless soil (Rankine's theory):

[ K_A = \tan^2 \left( 45^\circ - \frac{\phi}{2} \right) ]

Where:

• ( \phi ) = angle of internal friction of soil

Summary Diagram of Parameters

graph LR
    A[Wall Base Area (A)] --> B[Wall Width (B)]
    H[Wall Height (H)] --> M[Bending Moment (M)]
    KA -->|Active Earth Pressure| P[Pull (P)]
    Y[Unit Weight Soil (

IS 9527 Part 6 – Materials: Key Formulas, Tables & Specifications

1. Design Parameters (Clause 10.2.1)

• Derived from site investigations and laboratory tests.
• Includes soil properties, concrete density, friction angles, etc.

2. Important Symbols (Clause 4.1)

3. Coefficients of Static Friction (Clause 10.2.4.4, Table 1)

* Reduced to 0.7 if bed rock is brittle/cracked or sand movement is intensive.

4. Reference Indian Standards for Materials (Annex A, Clause 2.1)

Summary:

• Use site-specific soil and material parameters.
• Apply coefficients of friction from Table 1 for sliding stability.
• Follow referenced IS codes for material specifications and design practices.

flowchart TD
    A[Site Investigation] --> B

IS 9527 Part 6: Block Work Wharf Wall - Key Points

General Description (Clause 6.1)

• Gravity structure made of solid or cellular precast concrete blocks.
• Blocks placed on a prepared rubble bed (levelling course).
• Blocks must be shaped to avoid damage during transport and placement.

Design Criteria (Clause 10.1)

• Base width: Ensure max foundation pressure ≤ safe bearing capacity.
• No tension anywhere in the wall cross-section.
• Sliding safety factor ≥ 1.5.
• Overturning safety factor:
  • ≥ 1.5 with seismic forces included,
  • ≥ 2 without seismic forces.

Self Weight Computation (Fig. 3)

[ W = W_1 + W_2 + W_3 + W_4 ]

• (W_1): Dry weight of block work above HWL (High Water Level).
• (W_2): Dry weight of backfill on toe above HWL.
• (W_3): Submerged weight of block work below HWL.
• (W_4): Submerged weight of backfill on toe below HWL.

Detailed Design (Clause 10.4)

• Strength of blocks.
• Shape/dimensions of keys and lifting holes.
• Lifting gear specifications.
• Service galleries and ducts (side walls, roof slab).
• Pipe bollards design.

Summary Table: Safety Factors

flowchart LR
    A[Block Work Wharf Wall] --> B[Precast Concrete Blocks]
    A --> C[Rubble Bed (Levelling Course)]
    A --> D[Design Criteria]
    D --> E[Base Width: Pressure ≤ Bearing Capacity]
    D --> F[No Tension in Cross Section]
    D --> G[Safety Factor Sliding ≥ 1.5]
    D --> H[Safety Factor Overturning ≥ 1.5 (seismic), ≥ 2 (no seismic)]
    A --> I[Detailed Design]
    I --> J[Block Strength

IS 9527 Part 6: Types of Block Work - Key Points

Types of Block Work (Clause 7.0)

There are four main types of block work generally adopted:

1. Solid Block Work

   • Blocks are fully solid, providing good load-bearing capacity.

2. Hollow Block Work (Clause 7.4)

   • Hollow blocks are placed and later filled with concrete (by tremie or other methods) for enhanced strength and reduced weight.

3. Cavity Block Work

   • Two layers of blocks with a cavity in between for insulation.

4. Reinforced Block Work

   • Blocks reinforced with steel bars and filled with grout/concrete for higher load capacity.

Specifications (Clause 6.3 & 11.5.2)

• Block work is used where load-bearing soil exists at the foundation level.
• Block walls should conform to strength and stability requirements as per Clause 11.5.2.

Typical Design Considerations:

• Block dimensions: Usually 400 mm length × 200 mm height × 100-150 mm thickness.
• Filling material: Concrete grade M15 or as specified.
• Reinforcement: Steel bars as per design loads.

Summary Table for Block Types

flowchart LR
    A[Types of Block Work] --> B[Solid Block Work]
    A --> C[Hollow Block Work]
    A --> D[Cavity Block Work]
    A --> E[Reinforced Block Work]
    C --> F[Concrete Filling]
    E --> G[Steel Reinforcement]

For detailed design, refer to IS 9527 Part 6 clauses 6.3, 7.0, 7.4, and 11.5.2.

IS 9527 Part 6: Necessary Information for Design of Block Work Wharf Walls

Key Design Parameters (Clause 10.2 & 10.2.1)

• Design conditions from site investigation & lab tests (soil, water, load, etc.)
• Block dimensions & shapes (including key and lifting holes)
• Wall dimensions (initial assumption, then finalized)
• External loads (wave, current, surcharge, etc.)
• Stability checks:
  • Sliding
  • Overturning
  • Bearing capacity of foundation

Detailed Design Components (Clause 10.4)

• Block strength
• Key & lifting holes: Shape & dimensions for handling
• Lifting gear: Capacity & type to handle blocks safely
• Service galleries & ducts: Design of side walls & roof slabs
• Pipe bollards: Structural design

Typical Stability Checks Formulas

Block Dimensions & Keyhole Guidelines

• Block size: As per load & handling equipment capacity
• Key holes: Rectangular or circular; dimensioned for interlocking and lifting
• Lifting holes: Sized for lifting gear, avoid stress concentration

flowchart TD
    A[Site Investigation] --> B[Determine Design Conditions]
    B --> C[Assume Wall Dimensions]
    C --> D[Calculate Loads]
    D --> E[Check Sliding]
    D --> F[Check Overturning]
    D --> G[Check Bearing Capacity]
    E & F & G --> H[Determine Final Wall Dimensions]
    H --> I[Detailed Design: Blocks, Holes, Lifting Gear

IS 9527 Part 6 – Loads and Forces on Block Work (Wharf Walls)

Key Formulas and Parameters

• Total Self Weight, W
  [ W = W_1 + W_2 + W_3 + W_4 ] Where:

  • (W_1): Dry weight of block work above HWL
  • (W_2): Dry weight of backfill resting on toe above HWL
  • (W_3): Submerged weight of block work below HWL
  • (W_4): Submerged weight of backfill resting on toe below HWL

• Horizontal Forces Resultant, (R_H) includes:

  • Horizontal earth pressure with surcharge
  • Differential water pressure
  • Seismic horizontal earth pressure (during earthquake)
  • Mooring pull

• Factor of Safety (FoS):

  • Against sliding: (\geq 1.5)
  • Against overturning:
    • With seismic forces: (\geq 1.5)
    • Without seismic forces: (\geq 2.0)

• Sliding Check:
  [ \text{FoS} = \frac{p_w}{R_H} \geq 1.5 ] Where (p_w) = frictional resistance = (W \times \tan \phi) (soil friction angle)

• Overturning Check:
  [ \text{FoS} = \frac{M_R}{M_O} \geq 1.5 \text{ or } 2.0 ] Where:

  • (M_R) = stabilizing moment due to vertical forces
  • (M_O) = overturning moment due to horizontal forces

Earth Pressure Coefficients

• Use active earth pressure coefficients ((K_A)_s) for dry and submerged conditions based on internal friction angles.

Typical Load Diagram Components

flowchart LR
    A[Block Work Wall] --> B[Self Weight W]
    A --> C[Earth Pressure (Horizontal)]
    A --> D[Differential Water Pressure]
    A --> E[Mooring Pull]
    A --> F[Seismic

Design Considerations per IS 9527 Part 6

Key Design Sequence (Clause 10.2)

1. Determine design conditions from site investigations and lab tests.
2. Select block dimensions and shapes.
3. Assume initial wall dimensions.
4. Calculate external loads & forces.
5. Check sliding stability:
   [ \text{FS}_{sliding} \geq 1.5 ]
6. Check overturning stability:
   • With seismic:
     [ \text{FS}_{overturning} \geq 1.5 ]
   • Without seismic:
     [ \text{FS}_{overturning} \geq 2.0 ]
7. Check bearing capacity of foundation.
8. Finalize wall dimensions and detailed design.

Design Criteria (Clause 10.1)

• Base width: Ensure max foundation pressure ≤ safe bearing capacity.
• No tension in any cross-section.
• Safety factors: Sliding ≥ 1.5; Overturning ≥ 1.5 (with seismic), ≥ 2 (without seismic).

Self Weight Computation (Fig. 3)

[ W = W_1 + W_2 + W_3 + W_4 ]

• (W_1) = Dry weight of block above HWL
• (W_2) = Dry weight of backfill on toe above HWL
• (W_3) = Submerged weight of block below HWL
• (W_4) = Submerged weight of backfill on toe below HWL

Additional Notes:

• Block strength, lifting holes, and gear must be designed per Clause 10.4.
• Service galleries, ducts, and pipe bollards require separate structural design.

flowchart TD
    A[Site Investigation & Lab Tests] --> B[Determine Design Conditions]
    B --> C[Select Block Dimensions]
    C --> D[Assume Wall Dimensions]
    D --> E[Calculate Loads & Forces]
    E --> F[Check Sliding Stability]
    F --> G[Check Overturning Stability]
    G --> H[Check Bearing Capacity]
    H --> I[Finalize Design]

This structured approach ensures safety and

IS 9527 Part 6: Construction Procedures for Block Work (Hollow Blocks)

Key Points from Clauses:

• Clause 7.4 (Block Work with Hollow Blocks):

  • Hollow blocks are placed and then filled with concrete (using tremie or other methods).
  • Ensures composite action and strength.

• Clause 10.2.1 (Design Parameters):

  • Design parameters must be based on detailed site investigation and lab tests.
  • Includes soil properties, concrete strength, block dimensions, and environmental conditions.

• Clause 11.9.1 (Construction Coordination):

  • Use PERT/CPM networks for scheduling and coordination.
  • Foundation preparation is critical to avoid delays.

• Clause 8.1 (Necessary Information):

  • Detailed info from 8.2 to 8.8 (not provided) is essential for design and construction.

Typical Construction Steps for Hollow Block Work:

1. Foundation Preparation:

   • Level and compact soil/foundation bed thoroughly.

2. Block Placement:

   • Position hollow blocks accurately as per design.

3. Filling Hollow Blocks:

   • Use tremie method or direct pouring of concrete grout to fill blocks completely.

4. Curing:

   • Proper curing of filled blocks to achieve design strength.

Typical Parameters & Formulas (Generalized):

Example: Volume of Concrete per Block

[ V_c = V_{block} \times \text{(Hollow fraction)} ]

Where:

• (V_{block}) = block volume (length × width × height)
• Hollow fraction = % of block volume that is hollow (typically 50-60%)

Construction Workflow Diagram (PERT/CPM Concept)

graph TD
    A[Site Investigation] --> B[Design Parameter Finalization]
    B --> C[Foundation Preparation]
    C --> D[Block Placement]
    D --> E[

IS 9527 Part 6: Casting Yard & Block Production Key Points

Casting Yard (Clauses 3.12, 11.1.1)

• Paved surface: Must withstand heavy machinery, cranes, trucks.
• Area: Large enough for monthly block casting, material stacking, cement storage, water tanks, mixers, labor zones.
• Utilities: Continuous water supply (for casting & curing) and electrical connections.
• Surface strength: Hard pavement for movement of cranes and trucks.

Block Production (Clauses 10.2.2, 11.1.2)

• Block dimensions depend on:
  • Casting facility capacity
  • Crane hoisting limits
  • Transport vehicle capacity
  • Wall height & tidal range
  • Piling and joint integrity
  • Site conditions
• Daily casting schedule: Documented to optimize crane use and avoid double handling.

Practical Notes:

flowchart LR
    A[Material Storage] --> B[Mixing Area]
    B --> C[Casting Yard]
    C --> D[Block Curing Area]
    D --> E[Stacking & Transport]
    E --> F[Launching Site]

This layout ensures smooth workflow from raw materials to launching.

IS 9527 Part 6 — Handling of Concrete Blocks: Key Points

1. Block Size & Weight Considerations (Clauses 6.2, 10.2.2, 11.2.1)

• Block dimensions depend on:
  • Casting facility capacity
  • Crane hoisting capacity
  • Transport vehicle limits
  • Wall height & tidal range
  • Site conditions & elevation
• Block weight must allow easy handling with available equipment.
• Use special lifting gear to reduce handling cost.

2. Lifting Gear Design (Clause 11.2.1)

• Typical lifting gear includes:
  • Connecting beam with central hook
  • Two vertical shafts (65 mm diameter mild steel bars)
  • Tilting keys to lock blocks between wooden pieces
• Structural components must resist shear from block dead weight.
• Blocks can also be handled by strong slings or steel box sections.

3. Handling Procedure

• Place blocks between wooden pieces.
• Lock with tilting keys.
• Attach assembly to crane hook.
• Transport to desired location.

Sample Lifting Gear Schematic (Fig. 8 referenced):

graph TD
    A[Connecting Beam] --> B[Central Hook]
    A --> C[Vertical Shafts (65mm ø)]
    C --> D[Tilting Keys]
    E[Block] -- Wooden Pieces --> F[Between Shafts]
    B --> G[Crane Hook]

Summary Table: Block Handling Parameters

Ensure all handling equipment is designed for the maximum block weight and site-specific conditions to guarantee safety and efficiency.

IS 9527 Part 6: Foundation Preparation & Bed Leveling Key Points

1. Excavation & Cleaning (Clause 11.3.1)

• Excavate trench to designed size, slope, and levels.
• Remove loose silt, sand, and clay above founding level.

2. Bedding Material (Clause 11.3.2 & 3.2)

• Fill trench with rubble; top 200 mm layer of graded metal (50 mm size).
• Thickness of rubble depends on site conditions.
• If exposed rock found, use either:
  • Concrete layer, or
  • Thin graded metal layer (50 mm size).
• Bed can alternatively be formed with concrete or quarry run metal.

3. Leveling & Alignment

• Place steel frames across trench for alignment and levels.
• Control levels from shore using leveling instruments.
• Provide lateral gradient 1:100 inward on metal layer to counteract differential settlement due to backfill thrust.
• Frames stabilized with gunnys filled with metal.
• Alignment checked via vertical staff and theodolite from shore.
• Divers assist in positioning and signaling.

Summary Table

flowchart TD
    A[Excavate Trench] --> B[Remove Loose Silt/Sand/Clay]
    B --> C[Fill with Rubble]
    C --> D[Top 200 mm Graded Metal (50 mm)]
    D --> E[Place Steel Frames for Alignment]
    E --> F[Level & Align Using Theodolite]
    F --> G[Provide 1:100 Inward Gradient]
    G --> H[Stabilize Frames with Gunnys]
    H --> I[Block Work Construction]

This ensures stable, level foundation bed minimizing differential settlement and ensuring proper block placement.

IS 9527 Part 6: Block Launching and Placement – Key Points

1. Block Launching Definition (Clause 3.8)

• Blocks are lifted and placed vertically or slanting in contiguous fashion.
• Use crane or rig with diver assistance.
• Aim: Form wharf walls to predetermined sections.

2. Launching Methodology (Clause 11.4 & 11.4.1)

• Use heavy lift crane + lifting gear.
• Start from land with smaller rectangular blocks (~10 T).
• Progress towards sea in sequence.

3. Block Size & Shape Selection (Clause 6.2)

• Depends on:
  • Construction methodology.
  • Handling, transportation, and launching equipment capacity.

Typical Specifications & Considerations

Block Launching Workflow

flowchart LR
    A[Start at Land] --> B[Place Pre-Abutment Blocks (~10T)]
    B --> C[Use Crane with Lifting Gear]
    C --> D[Assist Divers for Accurate Placement]
    D --> E[Place Next Block Contiguously]
    E --> F[Progress Towards Sea]

Summary:
Block launching in IS 9527 Part 6 emphasizes safe, sequential placement using cranes starting with smaller blocks on land, progressing seawards, with block size tailored to equipment capacity and construction method.

IS 9527 Part 6: Monitoring and Stability Checks

Key Specifications & Formulas

• Design Parameters (Clause 10.2.1):
  Derived from detailed site investigations and lab tests to establish soil and material properties.

• Coefficients of Static Friction (Clause 10.2.4.4, Table 1):

*For cracked/brittle bedrock or intensive sand movement, reduce μ to ~0.7.

• Symbols & Parameters (Clause 4.1):

Typical Stability Checks

• Sliding Stability:
  [ F_s = \frac{\text{Resisting Forces}}{\text{Driving Forces}} \geq F_{\text{required}} ] Where resisting forces include friction (μ × normal force).

• Overturning Stability:
  [ F_o = \frac{\text{Moments resisting overturning}}{\text

IS 9527 Part 6: Quality Control and Alignment – Key Points

1. Tolerances (Clause 11.5)

• Tolerances ensure the constructed elements conform to design dimensions.
• Typical tolerances include:
  • Verticality: ±10 mm per 3 m height
  • Leveling of foundation and capping: ±5 mm
  • Alignment of blockwork: Controlled continuously to match design cross-section (Clause 11.8.2)

2. Design Parameters (Clause 10.2.1)

• Based on detailed site investigations and lab tests.
• Parameters include soil properties, load factors, and environmental conditions.

3. Alignment Control (Clause 11.8.2)

• Continuous monitoring of:
  • Foundation and blockwork levels
  • Slope of blockwork
  • Verticality of berthing face
  • Alignment of blockwork and capping concrete

4. Important Symbols (Clause 4.1)

Summary Table: Quality Control Checks