Geokon 4415, Instruction Manual, Page: 5 / 10

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1. INTRODUCTION
The Geokon Model 4415 3D Mechanical Crackmeters is designed to measure movement across
joints such as the construction joints in buildings, bridges, pipelines, dams, etc.; tension cracks in
soils and joints in rock and concrete.
The crackmeter comprises a horizontal square bar that is anchored on one side of the crack and a
three-sided box, in which the end of the square bar nests, anchored on the other side of the crack.
The anchors are made from two lengths of #4 rebar, six inches long, grouted into boreholes
drilled on either side of the crack. The crackmeter will measure any widening of the crack and
the extent of any shearing movements in two directions.
A typical installation of the 3D Mechanical Crackmeter is shown in Figure 1.
Figure 1 – Typical Installation
Once installed, measurements are made using a depth micrometer or dial gauge that is inserted
into each of the three access holes. Displacements (direction and magnitude) are determined by
comparing the base readings with the current readings.