Investigation of soil-geosynthetic-structure interaction associated with induced trench installation

The design of subsurface structures associated with transportation and other underground facilities, such as buried pipes and culverts, requires an understanding of soil-structure interaction. Earth loads on these structures are known to be dependent on the installation conditions. To reduce earth pressures acting on buried structures installed under high embankments, the induced trench method has been recommended and applied in practice for several decades. It involves the installation of a compressible material (e.g. EPS geofoam blocks) immediately above the buried structure to mobilize shear strength in the backfill material. A first step towards understanding this complex soil-geosynthetic-structure interaction and accurately modeling the load transfer mechanism is choosing a suitable material model for the geofoam that is capable of simulating compressive testing results. In this study, an experimental investigation is conducted to measure the changes in contact pressure on the walls of a rigid structure buried in granular backfill with an overlying geofoam layer. Validated using the experimental results, finite element analysis is then performed and used to study the role of geofoam density, thickness and location on the load transferred to the buried structure. Conclusions are made regarding the effect of modeling EPS inclusion as a non-linear material and the role of EPS configuration on the earth pressure distribution around the buried structure.