Measurement system with angular encoders for continuous monitoring of tunnel convergence

• CANG system allows continuous monitoring of convergences using encoders.
• CANG system allows the reconstruction of the shape of the tunnel perimeter.
• CANG system allows the movement of personnel and material in the tunnel.

This paper presents a system for measuring tunnel convergence called CANG (Convergence by means of ANGular Sensors) that enables monitoring of the positions of the points of a wire situated on the perimeter of the workings. This measuring system records the angles and lengths of each section of wire at all times, determining the shape of the wire and the convergence values.There is no need to remove the CANG system to allow the movement of personnel or material, as the wire is always kept close to the perimeter of the tunnel, freeing up most of its useable cross-section. It may therefore be left installed over long periods of time, thereby providing a continuous record of convergence.The mechanical and electronic components of this convergence system are reported, in addition to its pilot implementation in the Rellon road measurement tunnel located on the Autovía del Cantábrico dual carriageway in Asturias (northern Spain).