Analysis of soil conditions and pipe behaviour at a field site

Abstract

Water main pipes buried in expansive soils are often subjected to severe distress subsequent to installation. Excessive stresses may be induced due to either differential movement of the soils or swelling pressures from the soils along the pipes, impairing their performance or even breaking them. Field monitoring is an important means for understanding soil behaviour and its interaction with water mains. For this purpose, field instrumentation was successfully installed to monitor the performance of a section of water main placed in a well-developed area of a city neighbourhood where more frequent pipe breakage had occurred in recent years. The instrumentation included sensors to measure pipe wall strains, pipe displacement, in situ soil water content, soil pressure, and temperature. The instruments were installed in both the soil backfill and native soil around the backfill. This paper presents the analyses of monitoring data collected during the first 3 years after instrument installation. It was observed that the soil and pipe behaviour was affected significantly by soil properties and seasonal changes and correlated closely with the change pattern of the local meteorological conditions.