Guide for lateral dynamic load test on piles
1981 Edition

Overview of Scope & Essential Data for Pile Load Testing

Scope (Clause 3.1): Essential information required includes:

• Pile Characteristics:

  • Material type and reinforcement details
  • Installation technique (driven or cast-in-situ)
  • Depth, cut-off elevation, and cross-sectional dimensions

• Pile Positioning:

  • Location within pile group (test or working pile)
  • Condition at pile head (beneath cap or exposed to scour)

• Soil and Hydrogeology:

  • Subsoil layering profile
  • Groundwater table level

• Load Data:

  • Permissible and ultimate vertical load capacities
  • Actual design loadings including vertical, lateral, and moments

• Supported Structure and Load Nature:

  • Type of structure served
  • Loading conditions, including seismic effects

• Additional Inputs:

  • Previous testing experience
  • Other pertinent test planning information

Key Equation for Forced Vibration (Clause 6.3):

[ K = \text{Calibrated pick-up length (mm)} ]

Where:

• ( S ): Oscillograph paper speed (mm/s)
• ( m ): Oscillator eccentric mass (kg·s³/mm)
• Acceleration for 2g: ( 2 \times 9810 \text{ mm/s}^2 )

Appendix A: Proposes tabular formats to systematically record test parameters (Clauses 6.1–6.3).

Conceptual Diagram of Scope Inputs

graph TD
  A[Pile Load Test Scope] --> B[Pile Characteristics]
  A --> C[Location & Condition]
  A --> D[Soil Profile & Water Table]
  A --> E[Load Capacities]
  A --> F[Structure & Loading]
  A --> G[Additional Planning Data]

This framework ensures thorough preparation and execution of lateral pile load testing as per the standard.

Definitions and Key Parameters as per IS 9716

• Soil-Pile Stiffness (k_{ap}): Expressed as the dynamic force divided by static deflection amplitude from lateral load tests: [ k_{ap} = \frac{\text{Dynamic Force} (F)}{\text{Static Deflection} (x_{st})} ] Units typically in kg/cm.

• Reference Standards for Definitions:

  • IS 2810-1979 (Glossary of soil dynamics terms)
  • IS 2911 (Parts I to IV) (Pile foundation design and testing)
  • IS 5249-1977 (Dynamic soil characteristics)

• Parameters from Clause 1.40:

  • (k_{ap}): Soil-pile stiffness (kg/cm)
  • (A_z): Deflection coefficient at ground surface for free-headed piles
  • (E), (I): Modulus of elasticity and moment of inertia of the pile section (see Clause 6.8.1)

• Appendix A: Provides suggested tabular layouts for documenting dynamic test parameters such as force, displacement, and stiffness.

Table Summarizing Soil-Pile Stiffness Calculation

flowchart LR
    A[Conduct Dynamic Load Test] --> B[Measure Dynamic Force (F)]
    A --> C[Measure Static Deflection (x_st)]
    B --> D[Compute Soil-Pile Stiffness k_ap = F/x_st]
    C --> D
    D --> E[Apply k_ap in pile design and analysis]

Note: Detailed procedures and data formats are provided in Clauses 2.4, 6.7, 6.8.1 and Appendix A.

Information Needed to Conduct Forced Vibration Tests on Piles (IS 9716 Clause 3.1)

Essential Data Includes:

• Pile Details: Type, material composition, reinforcement, installation method (driven or cast-in-place).
• Dimensions: Length of pile, cut-off elevation, cross-sectional characteristics.
• Location Data: Positioning within the pile group, designation as test or working pile, condition (e.g., beneath cap or exposed to scour).
• Soil Profile: Subsurface strata description, groundwater table location.
• Load Information: Allowable and ultimate vertical load capacities, applied design loads including lateral forces and moments.
• Structure Details: Type and loading nature, including seismic considerations.
• Additional Notes: Previous testing experience and other relevant information for test planning.

Tabulated Record Format (Appendix A and Clause 7.1)

Important Equations:

• Frequency: [ f = \frac{n}{\text{Duration of Record (s)}} ]

• Absolute Acceleration: [ a = \text{Measured acceleration} \times \text{Calibration factors} ]

Testing Apparatus for Lateral Forced Vibration on Piles per IS 9716

Key Equipment Specifications (Clauses 3.1, 4.1, 6.1, 7.1):

• Testing Devices: As outlined in IS 5249-1977, including calibrated accelerometers, vibration generators, and recorders.

• Pile Information Required:

  • Type and reinforcement details
  • Installation method
  • Pile depth, cross-section, cut-off elevation
  • Piling layout and soil profile
  • Load capacities and design forces
  • Structure and loading type (e.g., seismic)

• Test Data Recording (Appendix A & Clause 7.1): Tabular format capturing vibration data:

Principal Formulas:

[ f = \frac{n \times S}{\text{Length of Record}} ]

[ A_z = \frac{\text{Absolute Acceleration}}{4 \pi^2 f^2} ]

[ F = m \times e \times 4 \pi^2 f^2 \times A_z ]

Where:

• (m) = Mass of oscillator or pile section
• (e) = Eccentricity (m)
• (f) = Frequency (Hz)
• (A_z) = Amplitude (m)

flowchart LR
  A[Calibrated Accelerometer] --> B[Data Acquisition]
  B --> C[Dynamic Force Computation]
  C --> D[Soil-Pile Interaction Analysis]

This equipment setup assures precise lateral dynamic testing aligned with IS 9716.

Guidelines for Pile Testing (IS 9716)

Preliminary Data (Clause 3.1):

• Pile specifics: material, reinforcement, installation technique.
• Geometry: length, cut-off level, cross-section.
• Location: pile group layout, test/working designation, condition.
• Soil profile and groundwater level.
• Load data: allowable and ultimate vertical loads, lateral design loads including moments.
• Structure type and loading nature (seismic or otherwise).
• Additional background information and prior experience.

Dynamic Test Setup (Clause 4.1.11):

• Employ a pulling mechanism (e.g., screw with clutch) to apply horizontal forces and sudden release for free vibration tests.

Testing Considerations (Clause 2.1):

• Pile response influenced by soil characteristics, superstructure constraints, sustained loads, and seismic excitation.
• Pile groups behave collectively; group effects must be considered.
• Numerical results should be rounded per IS 2:1960 rounding guidelines.

Typical Parameters & Equations:

Conceptual Diagram of Test Setup

graph LR
A[Pile] --> B[Clamp Attachment]
B --> C[Pulling Screw with Clutch]
C --> D[Applied & Released Horizontal Force]
A --> E[Soil Profile & Water Table]

Use this standard in conjunction with IS 2911 for comprehensive static and dynamic pile load assessments.

Guidance for Analyzing Lateral Dynamic Load Test Results (IS 9716 Clauses 7.1 & Appendix A)

Report Elements (Clause 7.1):

• Vibration data and tabulated results
• Graphical representations:
  • Soil-pile system response
  • Natural frequency
  • Damping ratio
  • Soil-pile stiffness
  • Soil modulus
• Illustrative figures and commentary

Example Tabular Data Format (from Appendix A)

Requirements and Recommended Formats for Test Reporting (IS 9716 Clause 7.1)

Mandatory Report Contents:

• Details of pile characteristics: type, depth, reinforcement, installation method
• Subsoil profile and groundwater information
• Test observations including vibration records, tables, and graphical plots
• Analytical results covering:
  • Soil-pile system natural frequency
  • Damping coefficient
  • Soil-pile stiffness
  • Soil modulus
• Illustrative figures and narrative remarks

Suggested Tabular Layout (Clauses 7.1 & Appendix A):

This comprehensive reporting ensures accurate interpretation of pile response under lateral dynamic loading, supporting design verification and safety assessments.

Key Formulas, Tables, and Formats from IS 9716 Appendices

Appendix A: Recommended Tabular Format for Forced Vibration Test Records (Clause 6.1)

Essential Equations:

• Dynamic Force: [ F = m \times e \times 4 \pi^2 f^2 \times A_z ] where:

  • (m) is the mass of the pile or oscillator section
  • (e) is eccentricity in mm
  • (f) is frequency in Hz
  • (A_z) is amplitude in mm

• Soil-Pile Stiffness: [ k_{ap} = \frac{\text{Dynamic Force}}{\text{Static Amplitude}} ] Units typically expressed as force per unit displacement (e.g., kN/mm).

Reporting Guidelines (Clause 7.1):

• Include detailed vibration records and plots illustrating soil-pile response
• Provide calculations and results for natural frequency, damping, stiffness, and soil modulus.