Load Reduction on Buried Rigid Culverts, Instrumented Case Histories and Numerical Modeling

Abstract

Three instrumented full-scale tests using geofoam (expanded polystyrene) for load reduction on buried rigid culverts are described. The culverts were built and instrumented during the period 1988–1992. The method involves installing a compressible inclusion (EPS Geofoam) above rigid culverts in order to reduce the vertical earth pressure. The first instrumented culvert is a concrete pipe with diameter 1.95 m beneath a 14 m high rock-fill embankment. The second full-scale test is a concrete pipe with diameter 1.71 m beneath a 15 m high rock-fill embankment. The third instrumented structure is a concrete box culvert with width 2.0 m beneath 11 m of silty clay. The long-term observations of earth pressure and deformation are presented, and compared with a simplified design method and finite element modelling using the finite element program, Plaxis 2D for the box culvert. The instrumentation consisted of hydraulic earth pressure cells, deformation and temperature measurements. The use of geofoam effectively reduces the vertical earth pressure, and long-term observations shows that the earth pressure is reduced to less than 30% of the calculated overburden in case of granular fill. Whereas the earth pressure is reduced to less than 50% of the calculated overburden in case of silty clay fill. The long term observations of earth pressure and deformation for more than 25 years show that the method using geofoam is stable over time. The last measurements were taken in 2015. The results from the numerical modelling are in agreement with the field measurements.