Construction methods · Site investigation and testing

Instrumentation and monitoring during construction

Measurement during the works: settlement plates under embankments, piezometers in soft clay, inclinometers behind excavations, strain and deflection on cantilevers and stays. It turns assumptions into data while there is still time to act.

How bridges get built · Site investigation and testing · Instrumentation and monitoring during construction

Also called: settlement monitoring, piezometers, inclinometers, structural health monitoring

How it is done

Install instruments before the load is applied: settlement plates and piezometers under approach fills, inclinometers beside cofferdams and deep excavations.
Set trigger levels (green, amber, red) tied to specific actions.
Read and plot at a frequency matching the rate of change; report against the predicted curves.
On cantilever and cable-stayed decks, survey the geometry every segment and adjust the next one.

Where it fits

Soft-ground approaches, deep excavations, balanced cantilever and stayed construction, launching.

Where it does not

Installing instruments without a plan for what to do when a trigger is reached.

Plant, pace and money

PlantInstruments, data loggers, survey total stations, sometimes automated systems.

ProductivityContinuous.

Cost0.5-2 % of the works it protects.

Risks and controls

What goes wrong

Damaged instruments during earthworks; data that nobody reads.

Quality assurance

Named person responsible for readings and for the trigger response; weekly plots in the progress meeting.

Examples

PVD-treated approaches are released for pavement only when settlement plates show the predicted consolidation; cantilever decks are cambered from survey data segment by segment.