Soil Pressure Reduction by Including Geofoam: A Numerical Study

Abstract

EPS geofoam has been increasingly used as a highly compressible geomaterial to reduce overburden stresses over various buried structures. Design guidelines are available to facilitate the applications of geofoams in a few countries. However, these existing design guidelines are primarily based on research and field results of shallowly buried, small-dimension structures, while completed studies on deeply buried, large-dimension culverts are still lacking. This study uses numerical simulation to assess and quantify effectiveness of geofoam that was used to protect deeply buried, large-span concrete culverts. The study was based on a real project, for which a concrete culvert of 5-m net span was buried underneath a filled roadway embankment. Geofoam of densities of 7.5 and 15 kg/m 3 were placed at different sections of the culvert to reduce overburden stresses. In this study, the soil and geofoam were simulated as non-linear plastic material and non-linear elastic material, respectively. The interface between soil and geofoam was simulated by Goodman contact elements that allowed in-plane slip but prevented penetration in normal direction. The construction was simulated by staged backfilling and executed in steps in the numerical model. The results disclosed that the geofoam was very effective to reduce the stress; however, the stress reduction varied significantly from different locations of the culvert. The highest stress reduction appeared at the culvert shoulder, which was approximately 90% and the average stress reduction was approximately 20%. Due to the crown shape of the culvert, a slight stress concentration was seen at the crown top of the culvert. In addition, according to this study the shoulder-to-shoulder coverage of geofoam seemed insufficient as there were significant increases of overburden stresses near the culvert shoulder. The numerical results further suggested that the geofoam shall not induce noticeable differential settlement if the backfill height exceeded the width of the geofoam. The numerical model suggested isoparametric elements be efficient in terms of computation time and Goodman contact elements, although can represent the interaction well, may cause excessive stress concentration.

Impact of Footing Shape on Dynamic Properties and Vibration Transmission Characteristics of Machine Foundations

“…Though the surface waves generally attenuate at a lesser rate than the body waves, their effect needs to be studied appropriately to mitigate the vibration-induced hazards [6]. The effect of such unwanted ground-borne vibration can be reduced by adopting various techniques such as modification of the attenuation characteristics of soil, application of wave barriers, or employment of damping devices in the form of base isolators [7][8][9]. Vibration mitigation using base isolators can be an efficient alternative for mitigating earthquake-induced vibration.…”

Guest Editorial for the Special Issue on “Sustainable Ground Improvement Technologies”

“…The third article by Wang and Huang [3] develops a numerical model and investigated the effect of geofoam on reducing overburden stresses for deeply buried culverts based on full-scale field monitoring data. The numerical model was developed under the framework of isoparametric element to improve the computation efficiency.…”