Engineered Ecoroof Systems: Geotechnical Considerations
Publication: Journal of Infrastructure Systems
Volume 22, Issue 3
Abstract
Ecoroof systems are proliferating to meet the need for reducing peak storm discharge and improving habitat in urban environments; however, no coherent set of standards exists for the engineering of these systems. Necessary questions that remain regarding engineering performance range from hydraulic to structural to geotechnical in nature, as exemplified in a series of recent ecoroof failures. As a first step, this paper describes a field exploration and laboratory characterization program conducted to develop a necessary geotechnical engineering baseline for ecoroof soils currently used with sustainable green-roof technologies. A series of low-stress (i.e., 10–30 kPa), static drained, simple shear tests were conducted on both reconstituted and relatively undisturbed specimens derived from three target gradations. The volumetric response of the undisturbed specimens exhibited contraction, and developed significantly larger magnitudes of volumetric strain than that of the reconstituted specimens, which exhibited a range in shear strain-dependent volumetric responses. The mobilized friction angle of the ecoroof materials ranged from approximately 37 degrees to 65 degrees, and varied as a function of organic content, normal stress, gradation, and relative density. The results show that the organic content has a significant effect on the stress-strain and volumetric responses of ecoroof soil in the field, which indicates that ecoroof design codes and standards are needed.
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Acknowledgments
This study was supported by the National Science Foundation under Grant CMMI No. 1162616; the authors are grateful for this support. The authors gratefully acknowledge the help of John Lambrinos, for his willingness to allow the investigators to sample ecoroof test plots at Oregon State University; Tom Liptan, for obtaining access to the sampled ecoroofs in Portland, Oregon; Zheng Li, for assisting throughout the field exploration; and Mary Ann Triska, for assisting at the beginning of the project.
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Published In
Journal of Infrastructure Systems
Volume 22 • Issue 3 • September 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Aug 7, 2014
Accepted: Jan 6, 2016
Published online: Mar 21, 2016
Discussion open until: Aug 21, 2016
Published in print: Sep 1, 2016
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