Global Level of Safety and Performance of Geosynthetic Walls: An Historical Perspective

Abstract

A summary of 20 well-documented geosynthetic wall case histories representing a total of 35 analysis conditions is presented. These case histories cover a wide variety of wall heights, surcharge loading, foundation conditions, facing types and batter, reinforcement types and stiffness, and reinforcement spacing. All of the production walls, including some that have been in service for 25 years, have performed well with low reinforcement strains and minimal deflections. Some of the walls were research structures that, although purposely underdesigned, could not be taken to failure, demonstrating that the internal stability design of geosynthetic walls in North America is conservative. Each of the walls was characterized globally with respect to internal level of safety, or resistance to demand ratio. Even when using nonconservative estimates of soil property values and perfect matching of the reinforcement strength to demand, the Simplified Method resulted in approximately 1.5 to 4 times as much geosynthetic reinforcement as that needed to achieve acceptable performance based on actual long-term performance of many of the wall case histories. Based on the analyses presented here, there is a need to re-evaluate the current North American approach to design of geosynthetic walls against internal reinforcement instability.

Evaluation of K-Stiffness Method for Vertical Geosynthetic Reinforced Granular Soil Walls in Japan

“…The six case studies originally reported by Allen et al (2002) that included a vertical wall face are summarized in Table 1. The reader is directed to the papers by Allen et al (2002Allen et al ( , 2003 and Allen and Bathurst (2002a, b) for a summary of the important details of these structures.…”

“…The reader is directed to the papers by Allen et al (2002Allen et al ( , 2003 and Allen and Bathurst (2002a, b) for a summary of the important details of these structures. However, since a major variable between structures is the facing type, it is useful to note that the wall facings include full-height and incremental precast concrete and aluminium panels, and geotextile wrapped-face type.…”

“…However, since a major variable between structures is the facing type, it is useful to note that the wall facings include full-height and incremental precast concrete and aluminium panels, and geotextile wrapped-face type. A vertical face wall with polymer strap reinforcement is reported in the original database by Allen et al (2002). However this wall was not re-examined here since the six additional case studies described below were all reinforced with continuous sheet polyoleˆn-based geogrid products.…”

“…Theˆrst objective of this paper is to extend the number of case studies collected by Allen et al (2002) by documenting and gathering data forˆve additional walls constructed in Japan and one additional wall constructed in the USA. The Japanese walls were part of a long-term project on large-scale testing of reinforced soil walls carried out by the Public Works Research Institute (PWRI) of Japan (PWRI et al, 1988;Ochiai and Fukuda, 1996;Tajiri et al, 1996).…”

“…However, the walls varied widely with respect to facing type. This new data set together with data for vertical walls previously published by Allen and Bathurst (2002a,b) and Allen et al (2002) is now used to isolate the eŠect of the facing stiŠness factor on reinforcement loads and to adjust the original equation that was developed to calculate its value. The paper also shows that predicted reinforcement loads using the current AASHTO Simpliˆed Method in the USA and the current PWRC method in Japan give the same reinforcement load predictions, and both grossly over-estimate the values deduced from measured strains.…”