Single-axis crack monitoring (opening)

What is crack opening monitoring?

Crack opening monitoring is used to assess the stability of structures affected by structural defects (differential movement, shrinkage, settlement, internal stresses or delayed-onset defects). When a linear crack develops along a dominant axis of displacement, usually horizontal or vertical, a single-axis sensor is the appropriate choice.

This type of monitoring applies in particular to cracks with parallel edges. Regular monitoring of the opening makes it possible to distinguish an active crack, which changes over time, from a stabilised defect, which determines the nature and urgency of the action required (enhanced monitoring, structural repair, protective measures, etc.).

Purpose of single-axis crack monitoring

Single-axis crack monitoring aims to measure precisely how the opening of a crack changes when the relative displacement of its edges occurs in one direction.

This type of monitoring applies to both vertical and horizontal cracks. The same measuring instrument is used in both cases: only its position changes, so that it is always perpendicular to the crack.

Maximum amplitude, rate of change, correlation with temperature, opening and closing cycles: these are all key indicators for analysing the phenomenon. The aim is to quantify precisely the variations in opening. Our instruments provide reliable monitoring, with a resolution of up to 0.01 mm.

How to measure crack opening?

Measurements can be taken manually or electronically using a single-axis measuring instrument.

Installing the single-axis crack monitor

Depending on the substrate and the type of instrument used, it can be bonded or mechanically fixed. The crack monitor is installed across the crack, perpendicular to it, in the main axis of the opening movement.

Precise positioning is essential to ensure reliable monitoring of the change in opening, at regular intervals, along a defined axis. This type of instrument measures only opening or closing movement. To monitor more complex displacements involving both opening and shear, two-way (2-axis monitoring) or three-dimensional (3-axis monitoring) measurement solutions will be required.

Collecting the data

Data can be read manually (removable mechanical or digital gauge) or transmitted continuously by a wireless system.

The choice of reading method (manual or automatic) depends on the duration of observation (one-off diagnosis or long-term monitoring plan), the accessibility of the cracked area and the required measurement frequency (every 24 h, every week, etc.).

Saugnac instruments for single-axis crack monitoring

The G1 gauge is a simple and robust instrument for manual single-axis crack monitoring. Easy to install and read, it offers a resolution of 0.1 mm and is ideal for one-off or regular monitoring that does not require automated data acquisition.

The E1 gauge is designed to monitor the development of cracks on one axis. Its digital display provides a precise reading of the opening at each measurement, with a resolution of 0.01 mm. Its patented removable system and carbon reference standard ensure repeatable measurements.

The R1 gauge is a measuring instrument with data transmission. It provides single-axis crack monitoring for structures requiring continuous monitoring (sensitive buildings, bridges, historic monuments). This linear sensor also offers a resolution of 0.01 mm.