Instrumentation for monitoring buried pipe behavior during backfilling

An extensive instrumentation plan was devised to monitor buried pipe behavior, soil behavior and pipe-soil, interaction during backfilling. The emphasis of the instrumentation plan was to monitor these parameters under different installation techniques without impeding construction operations. Different types and sizes of pipe were selected for installation in trenches excavated in undisturbed in situ soil conditions. Installation variables included in site soil conditions, trench widths, backfill material (including controlled low strength material), haunching effort, and compaction methods. A total of fourteen tests, each including reinforced concrete, corrugated steel, and corrugated HDPE, were conducted. Eleven of the installations were conducted with 900 mm inside diameter pipe and three with 1500 mm inside diameter pipe. The pipes were buried to a cover depth of 1.2 m. Measurements of pipe shape, pipe strains, pipe-soil interface pressures, soil density, soil stresses, and soil strains were collected. Pipe shape changes were measured by a custom built profilometer. Custom designed bending beam pressure transducers were used in the steel pipe to measure interface pressures. Most of the instrumentation performed well and measured results were within the range expected. Pipe-soil interaction effects were effectively measured with the instruments selected. Pipe shape changes were a very valuable parameter for investigating pipe-soil interaction.