Performance of an Induced Trench Installation

Abstract

An induced trench installation was instrumented to measure earth pressures both within the embankment and on the pipe. Deformations of the pipe and settlements within the embankment also were monitored. At the full height of the embankment, the average vertical and horizontal stress on the culvert remained relatively constant at 0.32 and 0.48 times the overburden stress, respectively. The pressures measured directly on the pipe compare favorably with other case histories presented within the literature and are in good agreement with the observed vertical elongation of the culvert. Pressure cells positioned within the embankment measured stresses roughly equal to the overburden stresses and indicate no significant redistribution of stresses other than those observed immediately around the pipe. The relative settlements within the embankment, above the induced trench installation, correspond with the design assumption that the fill within the prism of soil over the pipe settles downward relative to the adjacent fill. However, the recommended settlement ratio parameter used in the analysis, on the basis of geometry alone, may be questionable. That higher-than-expected lateral stresses on the pipe need to be considered in design was confirmed. Marston's formula and lower-bound input parameters appear to give a conservative estimate of the vertical loads on buried pipes.