Methodology guide

Mechanical admittance of piles: the Transient Response Method

Force, velocity and frequency response: what mechanical admittance testing using TRM can indicate about foundation piles.

An unusual signal is not yet a diagnosis. The client needs to establish what information supports the decision and which test can obtain it under the actual pile conditions.

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From impact to force–velocity data

TRM considers the applied impulse and the pile’s dynamic response. Force F must be acquired with the response; velocity V may be derived by integrating acceleration.

Force data distinguishes this analysis from echo-time interpretation alone. Acquisition quality and timing consistency affect the relationship subsequently processed.

Admittance in the frequency domain

Official SolGeo pages describe Fourier analysis of the V/F relationship. Admittance expresses the velocity response relative to force excitation in the frequency domain.

Resonances concern the pile–ground system and its restraints. Each peak cannot be treated as direct proof of a particular anomaly.

Length and inferred profile

TRM can contribute to indications of length and anomalies under the interpretive model’s assumptions. Characteristic frequencies should not become dimensions without explicit wave-velocity and boundary assumptions.

An inferred profile is an interpretation, not a direct diameter measurement along the pile. Neither a unique reconstruction nor undocumented accuracy is promised.

Preparation, limitations and comparison with PIT

An accessible, suitable head, geometric data, stratigraphy and construction records remain essential. Evaluate ground effects and structural connections when interpreting the response.

PIT and TRM may address different questions about the same pile; selection is not a commercial ranking. Reports distinguish observations, assumptions and assessment limits.

Related guides

PIT on foundation piles: how the Pulse Echo Test worksCross-Hole, PIT or mechanical admittance: which pile test should you choose?How to prepare a pile integrity test
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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

What information does your project need?

Share the objective, site constraints and required deliverables so we can assess an appropriate survey strategy.

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