Fracture Monitoring System of Sewer Pipe with Composite Fracture Sensors Via the Internet

Abstract

Sewer pipeline breaks were reported after severe earthquakes like the great Hanshin-Awaji earthquake in 1995. Although sewer pipeline breakage is not an emergent problem, they may cause epidemic disasters if left unrepaired. However, it is extremely expensive to find damaged parts and very time consuming to visually inspect all sewer pipelines laid underground. This demands a low-cost fracture monitoring system for sewer pipelines. The present study proposes a new fracture monitoring system for sewer pipelines and explains its demonstration using a small sewer pipe. The fracture monitoring system adopts fracture sensors made of fabric glass and carbon black–epoxy composite materials; a small embeddable terminal is included that can be connected to the Internet. In the sensor, a carbon black sheet is sandwiched between a surface layer and a base layer: both are made from fabric glass–epoxy plies. A part of the glass fibre in the surface layer is cut perpendicular to the loading direction to make a crack starter. Direct current electric voltage is charged in the embedded carbon black sheet; then, an electric resistance is connected serially to the carbon black sheet. Electric voltage of the resistance is monitored using the embeddable tiny terminal through the Internet. When the fracture sensor is loaded, large deflection causes a crack in the crack starter; then, the crack breaks the carbon black layer. This causes electric disconnection, and electric voltage of the resistance drops to zero. This system is applied to a fracture monitoring of a sewer pipe. As a result, the system successfully monitored fracture through the Internet.

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