Code of practice for design and construction of port and harbour structures, Part 4: Cellular sheet pile structures

IS 9527 Part 4 - Scope: Key Formulas, Tables & Specifications

Scope Summary:

• Covers design and layout of cellular sheet pile structures (circular & diaphragm types).
• Includes resistance to tilting using Cumming's method.
• Provides dimensions, number of piles, and spacing for circular cells.
• Specifies SI units for all quantities.

Key Formulas (Clause 6.3, Appendix A):

Resistance to Tilting (Cumming's Method):

• Resistance from soil prism (T_i): [ T_i = \text{Weight of soil in prism} \times \tan \delta_i ]

• Total resisting moment from soil fill: [ M_R = \sum T_i \times l_i ] where (l_i) = lever arm of prism (i).

• Resisting moment due to interlocking friction: [ M_I = P \times f \times B ]

  • (P) = interlocking friction force
  • (f) = friction coefficient
  • (B) = effective cell width

• Factor of Safety (FOS) against tilting: [ \text{FOS} = \frac{M_p + M_R + M_I}{M_a} ]

  • (M_p) = moment due to pile weight
  • (M_a) = applied moment causing tilting

Important Tables:

Table for Circular Cell Layout (Clause 4.1.1):

IS 9527 Part 4 — General Requirements: Key Formulas, Tables & Specifications

1. Resistance to Tilting (Cumming's Method) — Clause 6.3, Appendix A

• Soil Fill Resistance:

  • Divide soil into prisms (e.g., ajkd, amnp, abef).
  • Resistance due to prism (T_i = \text{Weight of soil in prism} \times \tan \delta_i)
  • Moments:
    [ M_R = \sum (T_i \times l_i) ]
  • Interlocking friction moment:
    [ M_I = P \times f \times B ] where (P) = interlocking friction force, (f) = coefficient of friction, (B) = effective width.

• Factor of Safety (FOS): [ FOS = \frac{M_P + M_R + M_I}{M_a} ] where (M_P) = moment due to pile weight, (M_a) = applied moment.

2. Layout Tables for Circular & Diaphragm Type Cells

• Circular Cell (Clause 4.1.1, Table):
  Defines number of piles, cell diameter, spacing, arc radius, etc.
  Example:

  No. of Piles	Diameter (m)	Spacing (m)	Area (m²)
  60	7.64	0.90	45.87
  100	12.74	1.98	127.44

• Diaphragm Type Cell (Clause 4.2, Table 2):
  Provides radius (R=C), height (H), and radius (r) per number of piles.
  Example:

  No. of Piles	(R=C) (m)	(H) (m)	(r) (m)
  10	4.20	0.56	0.76
  30

IS 9527 Part 4 — Materials and Protective Coatings

Key Specifications:

• Steel Pile Coating (Clause 3.3):
  • Apply one coat of primer on clean steel pile surfaces.
  • Follow with at least two coats of special marine paint before pitching and driving.
  • Refer to IS: 1419-1959 for paint specifications.

Resistance to Tilting (Appendix A, Clause 6.3):

• Soil fill resistance is calculated using Cumming's Method:

  For each soil prism: [ T_i = \text{Weight of soil in prism} \times \tan \delta_i ]

• Total resisting moment from soil fill: [ M_R = \sum (T_i \times \text{lever arm}_i) ]

• Resisting moment due to interlocking friction: [ M_I = P \times f \times B ] where:

  • (P) = interlocking friction force,
  • (f) = friction coefficient,
  • (B) = effective cell width.

• Factor of Safety: [ FS = \frac{M_p + M_R + M_I}{M_a} ] where:

  • (M_p) = moment due to pile,
  • (M_a) = applied moment.

Units (SI):

Circular Cell Layout (Clause 4.1.1):

• Cell diameter, pile spacing, and number of piles are selected from Table I.
• Number of piles is always even due to joint shape.
• Minimum cell radius with flat piles: ~3 m.

flowchart LR
    A[Soil Prisms] --> B[Calculate T_i = Weight × tan δ_i]
    B --> C[Calculate Moments M_R = Σ(T_i × lever arm)]
    C --> D[Calculate Interlocking Moment M_I = P × f × B]
    D -->

IS 9527 Part 4: Cellular Sheet Pile Structures

While the code excerpt lacks direct formulas or tables, typical key aspects from IS 9527 Part 4 and general practice include:

Types of Cellular Sheet Pile Structures

• Single Cellular Units: One cell formed by interlocking sheet piles with internal bracing.
• Double Cellular Units: Two cells side-by-side, increasing stiffness and load capacity.
• Multi-Cellular Units: Multiple cells for very large retaining or quay walls.

Key Specifications

• Cell Dimensions: Width and height depend on soil and load conditions; typical cell width ranges from 3m to 6m.
• Internal Bracing: Struts and tie rods designed for bending and axial forces.
• Material: Usually steel sheet piles conforming to IS 277 or IS 2911.

Typical Design Formulas

• Moment Capacity of Cell Wall: [ M = f_y \times Z ] Where:

  • ( f_y ) = Yield strength of steel (e.g., 250 MPa)
  • ( Z ) = Section modulus of sheet pile section

• Axial Load on Struts: [ P = \frac{M}{e} ] Where:

  • ( M ) = Moment in cell wall
  • ( e ) = Eccentricity (distance between cell wall and strut)

Typical Table: Cell Width vs. Load Capacity (Indicative)

graph LR
A[Single Cell] --> B[Internal Bracing]
A --> C[Sheet Piles]
D[Double Cell] --> B
D --> C
E[Multi Cell] --> B
E --> C

For detailed design, refer to IS 9527 Part 4 clauses on structural analysis and bracing design.

IS 9527 Part 4 — Design Considerations Summary

1. Diaphragm Type Layout (Clause 4.2, Table 2 & Fig. 2)

• Defines geometry of diaphragm cellular sheet pile structures.
• Key parameters for N piles:

2. Earth Pressure & Loading (Clause 5.2)

• Calculate earth pressures per:
  • IS 4651 (Part II) - 1969 (Earth pressures)
  • IS 4651 (Part III) - 1974 (Loading)

3. Resistance to Tilting (Appendix A, Clause 6.3)

• Use Cumming's Method:

  • Resistance from soil prisms: [ T_i = \text{weight of soil prism} \times \tan \delta_i ]
  • Total resisting moment: [ M_R = \sum (T_i \times \text{lever arm}_i) ]
  • Interlocking friction moment: [ M_I = P \times f \times B ]
  • Factor of Safety (FOS): [ FOS = \frac{M_p + M_R + M_I}{M_a} ] where (M_p) = moment due to pile weight, (M_a) = applied moment.

4. Circular Cell Layout (Clause 4.1.1, Table 4.1 & Fig. 1)

• Number of piles always even.
• Cell radius ≥ 3 m recommended.
• Example for 60 piles:

IS 9527 Part 4: Stability Requirements Summary

1. Tilting Stability (Clause 6.3 & Appendix A - Cumming's Method)

• Factor of Safety (FoS) against tilting ≥ 1.2
• Soil prism resistances calculated as:
  [ T_i = \text{Weight of soil prism} \times \tan \delta_i ]
• Resultant resisting moment from soil fill:
  [ M_R = \sum (T_i \times \text{lever arm}_i) ]
• Interlocking friction moment:
  [ M_I = P \times f \times B ] where:
  • (P) = interlocking friction force
  • (f) = friction coefficient
  • (B) = effective cell width
• Factor of Safety Formula:
  [ \text{FoS} = \frac{M_P + M_R + M_I}{M_a} ] where:
  • (M_P) = moment due to passive resistance
  • (M_a) = moment due to applied loads causing tilting

2. Sliding Stability (Clause 6.2)

• Factor of Safety against sliding ≥ 1.25
• Sliding resistance checked as per gravity structure principles.

3. Units (SI)

flowchart LR
    SoilPrisms -->|Weight x tan δ| TiltingResistance
    TiltingResistance -->|Sum moments| MR
    InterlockingFriction -->|P x f x B| MI
    MR & MI & MP -->|Sum moments| ResistingMoment
    AppliedLoad -->|Moment Ma| OverturningMoment
    ResistingMoment -->|FoS = (MP+MR+MI)/Ma| FactorOfSafety

Note: Use soil weight and friction angles from site investigation for precise calculations.

Key Formulas & Specifications for Construction (IS 9527 Part 4)

1. Resistance to Tilting (Cumming's Method) - Clause 6.3 & Appendix A

• Resistance due to soil prisms:

  [ T_1 = \text{Weight of prism ajkd} \times \tan \delta_2 ] [ T_2 = \text{Weight of prism amnp} \times \tan \delta_2 - T_1 ] [ T_3 = \text{Weight of prism abef} \times \tan \delta_2 - (T_1 + T_2) ]

• Resistance moment due to fill:

  [ M_R = T_1 \times l_1 + T_2 \times l_2 + T_3 \times l_3 + \ldots ]

• Resisting moment due to interlocking friction:

  [ M_I = P \times f \times B ]

  Where:

  • (P) = interlocking friction (from appropriate formulas)
  • (f) = friction coefficient
  • (B) = effective cell width

• Factor of Safety:

  [ \text{FOS} = \frac{M_p + M_R + M_I}{M_a} ]

  Where:

  • (M_p) = moment due to pile weight
  • (M_a) = moment due to applied loads

2. Circular Cell Construction - Clause 4.1.1

• Use Table of Number of Piles for cell diameter, spacing, and layout.
• Number of piles is always even; odd requires special piles.
• Minimum radius for flat-type sheet piles: ~3 m.

IS 9527 Part 4: Loadings and Forces - Key Formulas & Tables

1. Forces to Consider (Clause 5.1)

• Active lateral earth pressure (backside)
• Passive lateral earth pressure (front side)
• Lateral earth pressure of fill
• Residual water pressure
• Seismic forces on fill and backfill
• Mass of fill
• Vessel impact
• Bollard pull
• Wave forces
• Other site-specific forces

2. Resistance to Tilting (Cumming’s Method - Appendix A)

• Resistance due to soil prism (T₁, T₂, T₃, ...):
  ( T_i = \text{Weight of soil in prism} \times \tan \delta_i )

• Resistance moment due to fill weight:
  ( M_R = \sum T_i \times l_i ) (lever arms)

• Resisting moment due to interlocking friction:
  ( M_I = P \times f \times B )
  where

  • ( P ) = interlocking friction force
  • ( f ) = friction coefficient (0.3)
  • ( B ) = effective width of cell

• Factor of Safety:
  [ \text{FOS} = \frac{M_p + M_R + M_I}{M_a} ] where

  • ( M_p ) = passive moment
  • ( M_a ) = active overturning moment

3. Effective Width & Cell Dimensions (Clause 6.0)

4. Typical Layout Dimensions (Table from Clause 5.2)

| No. of Piles (N) | ( R = C ) (m) | ( H ) (m) | ( r ) (m) | |------------------|----------------

IS 9527 Part 4: Soil Support and Fill Materials - Key Points

1. Soil Support (Clause 6.5)

• Safety checks against piping, caving, and failure similar to retaining walls/footings.
• Bulkheads on hard soil/rock with well-drained fill are safe if:
  [ B = 0.8 \text{ to } 0.9 \times H ]
  where B = effective width of cell, H = height.

2. Soil Fill (Clause 3.2)

• Use freely draining, non-cohesive soil (e.g., coarse sand).
• Avoid fine sand prone to washing out.
• Other soils may be used with caution.

3. Resistance to Tilting (Clause 6.3 & Appendix A)

• Soil fill divided into prisms; resistance moments calculated by summing contributions of each prism.

• For prism (i), resistance force:
  [ T_i = \text{Weight of soil in prism} \times \tan \delta_i ]

• Total resisting moment due to soil fill:
  [ M_R = \sum T_i \times l_i ]

• Resisting moment due to interlocking friction:
  [ M_I = P \times f \times B ] where (P) = interlocking friction force, (f) = friction coefficient, (B) = cell width.

• Factor of Safety (FOS):
  [ FOS = \frac{M_p + M_R + M_I}{M_a} ] where:

  • (M_p) = moment due to passive soil pressure
  • (M_a) = moment due to active forces causing tilting

4. Water Saturation Line (Clause 5.3)

• When one side is dewatered, saturation line slope:
  • Common fill: 1 (vertical) : 2 (horizontal)
  • Special fill: 1 : 1
• Use dry bulk density above saturation line for calculations.

5. Units (SI)

• Length

IS 9527 Part 4: Structural Connections & Reinforcements Key Points

1. Resistance to Tilting (Cumming's Method) - Clause 6.3, Appendix A

• Soil fill resistance is modeled by dividing soil into prisms (e.g., ajkd, amnp).

• Resistance from each prism (T_i = \text{weight of soil in prism} \times \tan \delta_i).

• Total resisting moment due to soil fill: [ M_R = \sum (T_i \times l_i) ] where (l_i) = lever arm of prism (i).

• Interlocking friction moment: [ M_I = P \times f \times B ]

  • (P) = interlocking friction force (from formula)
  • (f) = friction coefficient (typically 0.3)
  • (B) = effective width of cell

• Factor of Safety: [ \text{FOS} = \frac{M_p + M_R + M_I}{M_a} ]

  • (M_p) = passive moment
  • (M_a) = active (overturning) moment

2. Circular Cell Layout - Clause 4.1.1, Table (No. of Piles)

• Number of piles always even.
• Cell diameter (D), spacing, arc radius, number of piles from table.
• Example: For 60 piles, diameter (D=7.64 m), spacing (=0.90 m), area (=45.87 m^2).

3. Diaphragm Type Cell Layout - Clause 5.2, Table 2

• Parameters:
  • (R = C) (radius = clear spacing)
  • (H) = height of cell above dredge line
  • (r) = radius of curved portion
• Example: For 10 piles, (R=4.20 m), (H=0.56 m), (r=0.76 m).

4. Symbols & Units (SI Units)

IS 9527 Part 4: Special Considerations — Key Formulas & Tables

1. Resistance to Tilting (Cumming's Method) — Clause 6.3 & Appendix A

• Cross-section: Cell width = B; soil fill up to line cd; soil prisms identified (e.g., ajkd, amnp).
• Resistance due to each prism:
  • ( T_1 = W_{ajkd} \times \tan \delta_2 )
  • ( T_2 = W_{amnp} \times \tan \delta_2 - T_1 )
  • ( T_3 = W_{abef} \times \tan \delta_2 - (T_1 + T_2) ), etc.
• Resistance moment due to soil fill: [ M_R = T_1 \times l_1 + T_2 \times l_2 + T_3 \times l_3 + \ldots ]
• Resisting moment due to interlocking friction: [ M_I = P \times f \times B ] where (P) = interlocking friction force, (f) = friction coefficient.
• Factor of Safety against tilting: [ FS = \frac{M_p + M_R + M_I}{M_a} ] where (M_p) = moment due to pile weight, (M_a) = applied moment.

2. Layout Tables

• Circular Cell (Clause 4.1.1, Table 1): Number of piles, cell diameter, spacing, arc radius, and area details for circular cells.
• Diaphragm Type Cell (Clause 4.2, Table 2): Radius (R = C), height (H), and radius (r) for given number of piles.

3. Earth Pressure & Loading

• Follow IS 4651 (Part II & III) for earth pressures and loading on cellular sheet piles.

4. Units & Symbols (SI Units)

Safety Factors and Checks as per IS 9527 Part 4

1. Tilting (Clause 6.3 & Appendix A - Cumming's Method)

• Factor of Safety (FoS) against tilting:
  [ \text{FoS} = \frac{M_p + M_R + M_I}{M_a} \geq 1.2 ] Where:

  • (M_p) = Moment due to weight of the cell
  • (M_R) = Moment due to weight of soil fill (sum of (T_1 l_1 + T_2 l_2 + T_3 l_3 + \ldots))
  • (M_I = P \times f \times B) (resisting moment due to interlocking friction)
  • (M_a) = Overturning moment

• Resistance due to soil prisms:
  [ T_i = \text{Weight of soil prism}_i \times \tan \delta_i ] where (\delta_i) is the friction angle of soil in prism (i).

2. Sliding (Clause 6.2)

• Factor of Safety against sliding:
  [ \text{FoS} \geq 1.25 ]
• Checked as for gravity structures considering soil friction and cohesion.

3. Shear (Clause 6.1)

• Safety against vertical shear failure at midsection must be verified (details in code).

Key Units (SI) for Calculations:

Summary Table:

flowchart TD