The Installation of Inclinometers in Saturated Granular Soils

Level crossings at Bonbeach, Chelsea and Edithvale in Victoria were removed through grade separation of the existing road and rail. Construction at each site included sheet pile supported rail trenches within Quaternary dune sands and coastal lagoon deposits. Prior to the excavation of the rail trenches, inclinometers were installed behind the sheet pile retaining walls to measure the variation in lateral ground displacement with depth during the excavation of the rail trenches. The installation of the inclinometers was found to be challenging due to the saturated and granular nature of the surrounding soils. The boreholes drilled were vulnerable to collapse when removing the drilling casing, while a significant loss of grout was experienced through permeable soils when installing the inclinometer casing. These ground conditions made it difficult to achieve consistent contact between the permanent inclinometer casing and the surrounding soil. The drilling and inclinometer installation methodologies implemented were progressively reviewed and then modified to mitigate these construction difficulties and improve the reliability of the inclinometers installed. This paper discusses the staged installation methodology which was developed and reviews the extent to which the newly adopted methodology was able to mitigate the initial construction difficulties encountered.