Reinforced Soil Structures with Poorly Draining Backfills. Part I: Reinforcement Interactions and Functions

Abstract

In this and a companion paper (Mitchell and Zornberg 1994), the use and performance of reinforced soil structures constructed with poorly draining and/or cohesive backfills is evaluated. This evaluation shows that proper design and construction can result in stable, durable, and economical earth structures. Permeable reinforcements may be especially useful for soil structures with poorly draining backfills because the drainage capabilities of the geosynthetic can dissipate excess pore water pressures, thus enhancing stability. Consequently, the design of a safe and economical structure should address two aspects specific to poorly draining backfills: the cohesive soil-reinforcement interaction and the reinforcement drainage characteristics. The present paper focuses on experimental and analytical studies undertaken to evaluate these issues. Tensile strength, durability, and creep response of geosynthetics embedded in marginal soils are also addressed. There is strong experimental evidence that permeable inclusions can effectively reinforce clay structures.

Experimental study of water infiltration on an unsaturated soil-geosynthetic system

“…Other investigations have focused their efforts on the behavior of geosynthetics as draining materials; however, in some cases these studies provide contradictory results. For instance, several authors have reported a satisfactory performance and effectiveness of the geosynthetics as a drainage layer [6][7][8][9][10]. Meanwhile, others have found that the geosynthetics do not always behave as a drainage material [11][12][13][14][15].…”

Geosynthetic capillary barriers: current state of knowledge

“…This is especially the case in earth retention systems involving poorly draining backfills, because of their higher susceptibility to develop positive pore water pressures (Zornberg and Mitchell 1994;Mitchell and Zornberg 1995). Geosynthetic drains have been proposed for use within these backfill soils to reduce the drainage paths.…”

Studies on the performance of geocomposite reinforced low-permeable slopes subjected to rainfall

“…Alternatively, it is possible to combine the drainage characteristics of a non-woven geotextile with the strength or stiffness of a stronger reinforcing geosynthetic like geogrid, thereby producing a hybrid geosynthetic, or geocomposite, as they are commonly referred to. Various researchers like Zornberg and Mitchell (1994), Christopher et al (1998), Koerner and Soong (2001) and Viswanadham (2010, 2011) have recommended the use of permeable inclusions as an effective alternative to relieve the pore pressure build-up due to marginal soil. Christopher et al (1998) and O'Kelly and Naughton (2008) also suggested the use of geocomposites in reinforced earth structures as a remedial measure, to provide both reinforcement and preferential drainage channels, thereby increasing the factor of safety for the slope.…”