Soil Pressure and Pipe Deformation Measurements for Characterizing Flexible Pipe-Soil Systems under Shallow Cover

A field test was performed to study the response of an 800 mm internal diameter, hybrid (plastic/metal) structured wall pipe during installation and varied traffic loading. Synchronized measurements were made of radial soil pressures adjacent to the pipe and pipe deflection, allowing representation of the pressure-deflection relationship of the soil-pipe system. Soil pressures were measured using null pressure measurement cells that avoid the effects of membrane deflection, soil stiffness, and stress history. It is concluded that the critical point in the lifetime of a flexible, shallow buried pipe is when the trench has been backfilled and compacted to the subgrade surface. At this point, the final pavement/asphalt layers have yet to be installed, yet very large loads may be traversing above the pipe section. Once the final pavement layers are constructed, the pressures reaching the pipe crown will become smaller, as will the respective deflections. As a result of the simultaneous and continuous measurement of soil pressure adjacent to the pipe and pipe deflections during the field test, a scheme has been suggested for approximate prediction of flexible pipe deflection in response to traffic loading. (C) 2017 American Society of Civil Engineers.