Guideline for Interpretation of Nondestructive Integrity Testing of Augered Cast-in-Place and Drilled Displacement Piles-PDF

PDF

Pdf Summary

This Deep Foundations Institute guideline provides practical advice for interpreting nondestructive integrity tests on augered cast-in-place (ACIP) and drilled displacement (DD) piles. Its central message is that test results must not be interpreted in isolation: sound evaluations combine NDT data with detailed installation records, nearby soil and groundwater information, and engineering judgment.

The guideline describes pile-head impact methods—impulse echo, impulse response, and impedance/profile analysis—as fast and relatively economical, but susceptible to soil resistance, pile geometry changes, and signal damping. Bulges or changes in soil stiffness can produce reflections that resemble necking. Down-hole methods, including single- and cross-hole sonic logging and gamma-gamma logging, provide more localized information but require access tubes and have their own limitations, such as tube debonding or restricted coverage. Thermal integrity testing is also discussed as an emerging method.

Installation records should document drilling behavior, grout or concrete volumes by depth increment, grout return, and reinforcement placement. These details help identify construction problems and explain apparent anomalies. Soil conditions matter because they influence both pile shape and test response; for example, soft soils may permit bulging, while loose saturated sands may be prone to caving or necking.

The guideline distinguishes an <strong>anomaly</strong> (an unusual test indication), a <strong>flaw</strong> (a departure from intended pile geometry or material), and a <strong>defect</strong> (a flaw that may impair performance or durability). An anomaly should be verified and its extent assessed before it is classified as a defect. Multiple test methods, comparison with nearby piles, and review of all available records can help resolve uncertainty.

If a defect is confirmed, engineers should assess its effect on capacity and durability, considering actual loads, material strength, and group redundancy. Options include reducing the pile’s rated capacity, redesigning the foundation, or installing replacement piles; significant repairs are often impractical. Timely communication among the testing practitioner, engineers, and contractors is essential.

Keywords

Deep Foundations Institute

augered cast-in-place piles

drilled displacement piles

nondestructive integrity testing

impulse echo

impulse response

impedance profiling

sonic logging

gamma-gamma logging

thermal integrity testing