What the reflectogram represents
A PIT reflectogram shows recorded response after impact against time. State the displayed quantity and processing: acceleration, derived velocity and filters are not interchangeable without explanation.
Before looking for anomalies, identify the initial event, time origin and response repeatability. Sign conventions and scales also influence visual interpretation.
Attributing a reflection to the toe
A late reflection may be consistent with the toe but requires comparison with expected length, wave velocity and signal characteristics. A clear return does not necessarily identify the pile bottom.
With T as round-trip time and Vm as assumed average velocity, L = Vm × T / 2. The estimate retains uncertainties in both terms and in the return attribution; the formula does not remove these assumptions.
Impedance changes and anomalies
Reflections before the toe return may suggest impedance changes. Geometry and material properties contribute alongside ground, restraints and pile-head conditions.
Peak shape alone cannot uniquely distinguish narrowing, material changes or disturbances. No invented reflectograms or unsupported diagnoses are presented without real records and contextual information.
Uncertain signals and interpretive reporting
A poorly recognisable toe return may limit length estimation. Repeated and consistent recordings help assess stability or disturbance, without guaranteeing interpretation for every pile.
Separate observed times, assumed velocity, estimated length, anomaly hypotheses and unassessable intervals. Further investigations should address the uncertainty identified rather than being prescribed automatically.
Related guides
Frequently asked questions
- Do integrity tests measure load-bearing capacity?
- No. They assess aspects of integrity or pile response within method limitations; they do not replace a load-capacity assessment.
- Which method is always best?
- None: the objective, access and pile conditions determine what information can be obtained.
- Is estimated length certain?
- No: it depends on velocity assumptions, identifying the response and boundary conditions.
References and documentary scope
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