Post-Earthquake Investigation of Several Geosynthetic Reinforced Soil Retaining Walls and Slopes During Ji-Ji Earthquake of Taiwan - Reinforced Soil Engineering: Advances in Research and Practice - page 290

structures (Chou et al., 1996) is based on the reinforced soil technology
developed by the Japan Railway Technical Research Institute. A design and
construction manual is also issued by the Taipei Society of Civil Engineers
(Chou et al., 1998).
In this paper, the performance of several geosynthetic reinforced soil
structures during the 1999 Ji-Ji earthquake is reported. The causes of failure are
identified and suggestions leading to design improvement are made.

2 SEISMIC DESIGN

The seismic design of reinforced soil structures is typically done using a
pseudo-static approach. A seismic coefficient is used to express the earthquake
inertia force as a percentage of the dead weight of the potential failure soil
mass. There are a few design procedures proposed in recent years, as briefly
mentioned below.
Ling et al. (1996, 1997) and Ling and Leshchinsky (1998) proposed a
pseudo-static analysis considering the internal (tieback) and external
(compound failure and direct sliding) stabilities of the reinforced soil
structures. The procedure is an extension of the design procedure proposed by
Leshchinsky (e.g., Leshchinsky et al., 1995). The result of study is compiled in
the form of design charts and also available for computerized design
(Leshchinsky, 1997, 1999). The authors then extended the procedure for a
permanent displacement analysis.
From a series of parametric studies, the authors concluded that in the event
of a large earthquake, external stability, typically by direct sliding, may govern
the design. That is, a longer geosynthetic length is required for design in addition
to a stronger reinforcement in resisting the earthquake inertia force. The proposed
procedure was verified with 8 case histories for the 1994 Northridge earthquake
(M ¼ 6.7), the 1995 Kobe earthquake (M ¼ 7.3), the 1993 Kushiro-oki

earthquake (M ¼ 6.7).

Among all these cases, only the Tanata Wall of Kobe earthquake was relevant for
the verification of permanent displacement.
The effect of vertical acceleration on the performance of geosynthetic
reinforced soil structures was also studied by Ling and Leshchinsky (1998).
Vertical acceleration increases the required reinforcement length and force. It
was also concluded that the vertical acceleration may reduce the stability,
especially for direct sliding mode, if the corresponding horizontal component of
acceleration is very large.
A separate seismic design procedure was proposed by Bathurst and Cai
(1995) and Bathurst and Alfaro (1997). The procedure was based on an extension
of Mononobe-Okabe analysis. The procedure was subsequently adopted for

7.8) and the 1987 Chiba-ken Toho-oki earthquake (M ¼