Code of practice for design and construction of pile foundations, Part 4: Load test on piles

IS 2911 Part 4: Scope Summary

• Scope: This part of IS 2911 covers the design and construction of cast-in-situ bored cast-in-place piles.
• It includes definitions (Clause 2.0) relevant to pile foundations.
• Specifies load tests such as the CRP (Conventional Repeated Pile) test for determining ultimate load capacity (Clause 6.4, Appendix B).
• Routine load test requirements: Test load = 1.5 × estimated safe load or displacement limit of 12 mm, whichever is earlier (Clause 8.6).
• Provides load-penetration curves (Clause 12.5, Table B-2) for predominantly end-bearing piles to assess ultimate load capacity.

Key Formula for Routine Load Test (Clause 8.6):

[ P_{test} = \min \left( 1.5 \times P_{safe}, \quad \text{Load causing } 12 \text{ mm displacement} \right) ]

Load Penetration Table Excerpt (Clause 12.5):

(Refer to IS 2911 Part 4, Table B-2 for detailed values)

This standard ensures safe design and testing protocols for bored cast-in-situ piles, emphasizing load testing and data recording for reliable foundation performance.

IS 2911 Part 4 - Definitions & Key Specifications

1. Definitions (Clause 2.0)

• The standard defines terms related to pile foundations such as end bearing piles, friction piles, ultimate load capacity, and penetration.
• These definitions ensure uniform understanding for design, testing, and construction.

2. Ultimate Load Capacity (Clause 12.5, Table B-2)

• Load capacity is related to penetration depth during the Crucial Resistance Penetration (CRP) test.
• Sample data for 3B predominantly end bearing piles:

(Exact load values vary per test, refer to IS 2911 Part 4 Appendix B)

3. CRP Test (Clause 6.4, Appendix B)

• Used to determine pile load capacity by measuring load vs. penetration.
• Analysis per Fig. 2 (Clause 2.1.1) involves plotting load-penetration curve to find ultimate load.

Summary:

• Ultimate load capacity is derived from CRP test penetration data.
• Definitions standardize pile types and test methods.
• Refer to Appendix B for detailed test procedure and load-penetration curves.

graph LR
A[CRP Test] --> B[Measure Penetration]
B --> C[Plot Load vs Penetration]
C --> D[Determine Ultimate Load Capacity]

For exact formulas and test procedures, consult IS 2911 Part 4 Appendix B and Clause 12.5 tables.

IS 2911 Part 4: General Requirements for Pile Load Tests

1. Routine Test Frequency (Clause 4.2)

• Typically 0.5% of total piles tested.
• Can increase to 2% based on:
  • Structure type
  • Soil strata condition
  • Specific functional requirements

2. Information Required Before Testing (Clause 3.1)

• Pile details: Type, material, reinforcement, group arrangement
• Installation: Driving method and records
• Dimensions: Depth and cross-section
• Test type: Static, dynamic, cyclic, etc.
• Layout: Position and spacing, especially for group tests
• Soil: Water table depth, strata, and soil test results
• Load capacities: Safe and ultimate loads, calculation methods
• Reaction system: Availability of piles, anchors, kentledge
• Loading plan: Nature of load, free-standing pile considerations (e.g., scour)
• Additional info: Past experience and planning details

3. Types of Tests (Clause 6.3 & 6.4)

• Static Load Test
• Cyclic Load Test (Appendix A)
• Constant Rate of Penetration (CRP) Test (Appendix B)

Summary Table: Routine Test Frequency

flowchart TD
    A[Start: Planning Pile Tests] --> B[Collect Pile & Soil Info]
    B --> C{Determine Test Type}
    C -->|Static| D[Conduct Static Load Test]
    C -->|Cyclic| E[Conduct Cyclic Load Test]
    C -->|CRP| F[Conduct CRP Test]
    D --> G[Analyze Results]
    E --> G
    F --> G
    G --> H[Decide Safe Load & Safety Factors]

Note: Refer to IS 2911 Part 4 Appendices for detailed test procedures and load application rates.

IS 2911 Part 4 - Types of Load Tests on Piles

Types of Load Tests (Clause 4.0)

• Initial Test: Conducted on a single pile to verify design assumptions.
• Routine Test: Conducted on subsequent piles to confirm uniformity.

Loading Types

• Vertical Load Test
• Lateral Load Test
• Pullout Load Test

Key Test Information (Clause 3.1)

• Pile type, material, reinforcement
• Driving method and record
• Pile depth & cross-section
• Test type desired
• Pile layout and spacing
• Water table & soil strata details
• Safe and ultimate load capacity
• Reaction system details (piles/anchors/kentledge)
• Loading plan and scour considerations

Load Test Methods (Clause 6.1 & 6.3)

• Maintained Load Method: Load applied via hydraulic jack; settlement recorded by dial gauges.
• Cyclic Load Test: Repeated loading cycles applied; useful for dynamic or fatigue assessment.
• CRP Method: Alternative specialized method (details in Clause 6.4).

Typical Load Test Setup (Simplified)

graph LR
A[Hydraulic Jack] --> B[Pile Top]
B --> C[Load Frame / Reaction System]
C --> D[Ground / Anchors]
B --> E[Dial Gauges for Settlement]

Important Notes:

• Safe load is usually taken as the load at which settlement rate stabilizes or a specified limiting settlement is reached.
• Cyclic load tests help simulate real-life repetitive loading conditions.
• Reaction system must be capable of resisting applied loads without movement.

For detailed procedures, refer to IS 2911 Part 4 Clauses 6.1 to 6.4 and Appendix A.

IS 2911 Part 4: Test Setup and Equipment - Key Points

1. Pre-Test Information (Clause 3.1)

Before testing piles, collect:

• Pile details: type, material, reinforcement, group layout.
• Installation method: driving technique and records.
• Pile geometry: depth, cross-section.
• Test type: static, dynamic, cyclic, etc.
• Layout & spacing: single/group pile position.
• Soil & water table: strata details and test results.
• Load capacity: safe and ultimate load estimates.
• Reaction system: availability of piles, anchors, or kentledge.
• Loading plan: nature and special conditions (e.g., scour).
• Additional info: past test experience, planning data.

2. Types of Tests (Clause 8.6)

• Routine Test Load:
  [ P_{test} = \min(1.5 \times P_{safe}, \text{load at } 12 \text{ mm displacement}) ]
• Test load applied up to 1.5 times safe load or 12 mm displacement, whichever occurs first.

3. Data Recording and Presentation (Clause 6.3)

• Follow Appendix A for cyclic load test data recording.
• Follow Appendix B for CRP (Constant Rate of Penetration) test procedures.

Summary Table: Routine Load Test Criteria

flowchart LR
    A[Pre-Test Info Collection] --> B[Test Type Selection]
    B --> C[Setup Reaction System]
    C --> D[Apply Load (1.5 × Safe Load or 12 mm Disp.)]
    D --> E[Record Data (Appendix A/B)]
    E --> F[Analyze & Present Results]

This concise framework ensures compliance with IS 2911 Part 4 for pile load testing setup and equipment.

Vertical Load Test (Compression) — IS 2911 Part 4

Key Formula for Elastic Compression of Pile (Clause 2.1.4):

[ A = \frac{(T - F) \times L}{E \times A_c} ]

Where:

• ( A ) = Elastic compression of pile (cm)
• ( T ) = Load on pile top (kgf)
• ( F ) = Frictional resistance (kgf)
• ( L ) = Length of pile (cm)
• ( A_c ) = Cross-sectional area of pile (cm²)
• ( E ) = Modulus of elasticity of pile material (kgf/cm³)

Test Procedure (Clause 6.1):

• Apply compression load via hydraulic jack against a reaction frame.
• Measure settlement using dial gauges or compressometer (ideally at cut-off level).
• Use Maintained Load Method for safe load determination.
• Alternate methods: Cyclic Load Test and Constant Rate of Penetration (CRP).

Data Recording (Clause 9.1):

• Record Load, Displacement, and Time sequentially.
• Tabulate data with pile details for analysis.

Notes:

• Elastic compression correction is vital if test is not done at cut-off level (Clause 5.4).
• Separation of skin friction and point resistance can be analyzed from cyclic load test data (see Fig. 2 in IS 2911 Part 4).

flowchart TD
    LoadApplied[Load Applied on Pile Top]
    Settlement[Settlement Measured]
    DataRecorded[Record Load, Displacement, Time]
    Analysis[Analyze Data for Safe Load]
    
    LoadApplied --> Settlement --> DataRecorded --> Analysis

This summarizes the essentials for vertical compression load testing per IS 2911 Part 4.

IS 2911 Part 4: Lateral Load Test on Piles — Key Points

1. Test Preparation (Clause 3.1)

• Pile details: type, reinforcement, group layout
• Installation: driving method, records
• Geometry: pile depth, cross-section
• Test type & layout: single/group, space available
• Soil & water table: strata, test results
• Load capacities: safe & ultimate with basis
• Reaction system: piles, anchors, kentledge
• Loading plan: increments, free-standing piles if scour expected

2. Test Method (Clause 7.1)

• Use hydraulic jack between two piles/groups or suitable reaction
• Load applied in ~20% increments of estimated safe load
• Full jack load = lateral resistance per pile/group

3. Data Recording (Clause 9.1)

• Record load, displacement, and time sequentially
• Tabulate results with pile info for analysis

Typical Load-Displacement Data Table Format

Summary Diagram (Load Application)

graph LR
A[Pile 1] -- Hydraulic Jack --> B[Pile 2]
B -- Reaction --> C[Anchor/Kentledge]

Note: CRP method (Clause 6.4) is for ultimate capacity, not settlement prediction; routine tests use maintained load test.

Pull-Out Test on Piles (IS 2911 Part 4 - 1985)

Key Specifications:

• Test Setup:

  • Hydraulic jack rests on rolled steel joists supported on ground.
  • Supports must be at least 2.5 D away from pile periphery (D = pile diameter or circumscribing circle diameter for square piles).
  • Jack pulls the pile upward; reaction transferred to ground via supports.
  • Framework attached to pile top via reinforcement bars (threaded or welded bolts) or centrally embedded rods designed for load transfer.

• Reinforcement:

  • Pile must have adequate steel to withstand pull-out tension.
  • Additional reinforcement may be required to resist neck tension.

• Test Data:

  • Record Load, Displacement, and Time sequentially.
  • Data tabulated along with pile details.

Important Notes:

• For larger loads, multiple rods may be used symmetrically.
• Pile groups should be tested under actual use conditions.

Diagram of Pull-Out Test Setup

graph TB
    A[Hydraulic Jack] -->|Pushes| B[Steel Joists]
    B -->|Supported by| C[Ground Supports (≥ 2.5D away)]
    A -->|Pulls| D[Test Pile]
    D -->|Reinforcement Bars / Central Rod| E[Load Transfer]

Summary Table: Support Distance

This ensures safe and accurate pull-out load measurement per IS 2911 Part 4.

IS 2911 Part 4 - Recording of Data and Presentation

Key Points from Clauses 9.1 & 9.2:

• Variables to Record:

  • Load (P)
  • Displacement (Δ)
  • Time (t)

• Data Recording:

  • Sequential recording of load, displacement, and time during pile tests.
  • Use a tabular format including pile details (dimensions, type, test conditions).

• Presentation:

  • Plot Load vs Displacement curves — essential for interpreting pile behavior.
  • Safe load should be clearly indicated on graphs.
  • Additional curves (e.g., Load vs Time) may be drawn for comprehensive analysis.

From Clause 8.6 (Routine Test):

• Test load = 1.5 × estimated safe load or displacement limit = 12 mm total displacement, whichever occurs first.

Sample Data Table Format:

Load-Displacement Curve (Example):

graph LR
A[Load (kN)] --> B[Displacement (mm)]
B --> C[Safe Load Point]

Summary: Record load, displacement, and time sequentially; tabulate data; plot load-displacement curves highlighting safe load; limit test load to 1.5 times safe load or 12 mm displacement.

IS 2911 Part 4: Cyclic Load Test Method (Clause 6.3 & Appendix A)

Purpose:

• To determine skin friction and point bearing capacity separately on uniform diameter single piles.

Test Setup (Clause 6.1):

• Load applied by hydraulic jack against a reaction frame.
• Settlement measured by dial gauges.
• Cyclic method is an alternative to maintained load method.

Key Specifications:

• Load cycles: Load is applied cyclically (loading and unloading).
• Load magnitude: Typically up to 1.5 times the estimated safe load or until 12 mm settlement, whichever occurs first (Clause 8.6).
• Data: Settlement vs load recorded for each cycle (Clause 9).

Typical Procedure (Appendix A):

1. Apply cyclic load increments.
2. Record settlement after each cycle.
3. Separate skin friction and point bearing by analyzing load-settlement behavior.

Important Notes:

• Cyclic loading helps identify pile behavior under repeated loads.
• Instrumentation may be used for detailed analysis.

Summary Table:

flowchart TD
    A[Start Test] --> B[Apply Cyclic Load]
    B --> C[Measure Settlement]
    C --> D{Settlement < 12mm & Load < 1.5× Safe Load?}
    D -- Yes --> B
    D -- No --> E[Analyze Data]
    E --> F[Separate Skin Friction & Point Bearing]
    F --> G[Determine Safe Load]

This method provides a detailed understanding of pile capacity under repeated loads, crucial for design validation.

IS 2911 Part 4 — CRP Test Method (Clause 6.4 & Appendix B)

The CRP (Constant Rate of Penetration) test is an initial pile load test method to determine ultimate bearing capacity.

Key Points:

• Purpose: Determines ultimate bearing capacity, not suitable for settlement prediction.
• Not for routine tests.
• Load/deflection behavior differs from maintained load tests.

Procedure Summary (Appendix B):

• Apply load at a constant penetration rate (e.g., 0.5 to 1.0 mm/min).
• Record load vs. penetration until failure or maximum load.
• Plot load-penetration curve to find ultimate load (sharp increase in penetration for small load increment).

Key Formula:

• Ultimate Bearing Capacity, Q_u: Load at which penetration sharply increases.

Interpretation:

• The curve is nonlinear; the failure point is where load no longer increases significantly with penetration.
• Cannot be used for service load settlement prediction.

Comparison with Maintained Load Test:

graph LR
A[Start CRP Test] --> B[Apply Load at Constant Penetration Rate]
B --> C[Record Load vs Penetration]
C --> D{Penetration Increases Sharply?}
D -- No --> B
D -- Yes --> E[Determine Ultimate Bearing Capacity]
E --> F[End Test]

For detailed stepwise procedure and instrumentation, refer to Appendix B of IS 2911 Part 4.

IS 2911 Part 4: Analysis of Results for Frictional Resistance

Key Formulas

Given:

• ( P ) = Point bearing (kgf)
• ( F ) = Skin friction (kgf)
• ( T ) = Total load (kgf)
• ( S ) = Settlement (mm)
• ( m ) = Slope parameter (from graph)
• ( L, A, E ) = Length, area, and modulus parameters of the pile (used in elastic deformation)

Simultaneous Equations (Clause A-2.2.3):

[ T = P + F ]

[ S = mP + \frac{(T - F)^{2} L}{A E} ]

Solve these simultaneously to find ( P ) and ( F ).

Graphical Method (Clause A-2.1)

• Draw a straight line parallel to the linear portion of the load-settlement curve.
• This line divides the total load into point bearing (P) and skin friction (F).
• Repeat the procedure iteratively (Clause A-2.1.6) to refine ( F ).

Summary Table for Analysis

Conceptual Mermaid Diagram

graph LR
A[Total Load (T)] --> B[Divide into Point Bearing (P) and Skin Friction (F)]
B --> C[Use Load-Settlement Curve]
C --> D[Draw Parallel Line to Linear Portion]
D --> E[Estimate P and F]
E --> F[Iterate for Refinement]
F --> G[Solve Simultaneous Equations]

**