Initial Pile Pull-Out Test

1. Introduction

A pile pull-out test, also known as an uplift or tensile load test, evaluates a pile’s resistance to an upward force. It helps assess uplift capacity, pile displacement and the interaction between the pile surface and surrounding soil.

This blog outlines the initial pull-out test carried out at the HMI New Canteen project site in Mevalurkuppam, Tamil Nadu, with reference to IS 2911 (Part 4):2013.

2. Purpose of the Test

• Assess the pile’s uplift resistance under applied tensile loading.
• Measure vertical uplift displacement at different load stages.
• Review design assumptions related to uplift resistance.
• Study the load–displacement response and pile–soil interaction.

3. Applications

Uplift forces may arise from wind, hydrostatic pressure and other tensile actions. Pull-out testing can support the assessment of pile foundations used for transmission towers, basements, retaining structures and other structures subject to uplift.

4. Project Overview

5. Equipment Used

6. Test Arrangement

The reaction beams are supported on concrete pedestals or another suitable reaction system. A hydraulic jack is positioned in line with the pile connection and arranged with steel plates and high-strength connecting rods to apply the upward force. Independent datum bars and dial gauges are installed to measure pile uplift without disturbing the reference system.

7. Test Procedure

1. Inspect the jack, reaction beams, connecting rods, dial gauges and reference frame before testing.
2. Confirm that the reaction system is stable, sufficiently rigid and properly aligned.
3. Set the dial gauges to zero and verify the calibration status of the load-measuring device.
4. Apply the uplift load in controlled increments; the referenced procedure generally used increments of about 20% of the estimated safe uplift load.
5. Maintain each load stage for the specified observation period or until the displacement rate becomes negligible.
6. Record dial-gauge readings at the required observation intervals.
7. Continue loading up to the specified test load or the applicable limiting condition.
8. Unload in suitable decrements and record rebound or recovery.
9. Plot the load–uplift displacement curve and review the pile response.

8. Field Investigation Gallery

Selected photographs from the pull-out test and field investigation:

9. Conclusion

The reported pile sustained a maximum applied load of 70.14 MT against a stated design load of 28 MT. The source report describes low measured uplift displacement and significant elastic recovery and concludes that the pile performance was satisfactory for the stated design load.

10. Reference

IS 2911 (Part 4):2013 – Code of Practice for Design and Construction of Pile Foundations – Load Test on Piles.