Geosynthetics April/May 2024 - 16

Geosynthetics embankment with seismic resilience for highway
Although the highway extension inevitably
encountered the Chelungpu fault and
faced significant difficulties, it still needed
to be completed because of the government's
policy. However, by adjusting the
highway's topography, alignments, and
service functions, the difficulties were
finally minimized to a specific section
from Sta. 23k+242 to Sta. 23k+410.
FIGURE 2 Catastrophic damage caused by 921 Chi-Chi earthquake.
by these faults are almost countless, posing
a significant threat to people's lives
and property. For example, in 1999, the
Chelungpu fault in central Taiwan, one of
this island's most densely populated areas,
triggered the deadly 921 Chi-Chi earthquake,
which measured 7.3 on the Richter
scale. It caused approximately 14,000
fatalities and injuries, severely damaged
thousands of infrastructure facilities, and
toppled more than 100,000 houses. The
earthquake caused a seismic rupture zone
nearly 52 miles (85 km) long on the surface
from north to south along the foothills
of the hilly eastern area. The vertical
displacement was about 13.1 to 16.4 feet (4
to 5 m) in this area, as shown in Figure 2,
and the horizontal displacement was about
8.2 to 16.4 feet (2.5 to 5 m) in some areas.
Taichung, the largest city in western
FIGURE 3 Experimental and numerical results
of the unreinforced foundation (above) and
reinforced foundation (below).
16
Geosynthetics | April May 2024
Taiwan, has a highly concentrated population
and economy. Because of the increasing
traffic demand, the highway authority
had to quickly promote the extension
of National Highway No. 4 to provide
convenient transportation services to the
metropolitan area and surrounding cities.
Overview of geosynthetics
for fault mitigation
Yang et al. (2020) and Chiang et al. (2021)
conducted studies examining fault movements'
impact on GRS foundations. As
seen in Figure 3, they used sandbox
model tests and finite element numerical
simulations to analyze the results. The
study found that the reinforcement of the
foundations acted as a tension membrane,
creating vertical resistance to support the
overlying soil and minimizing the impact
of surface settlement. Other studies have
also verified that an adequately designed
GRS structure is effective in seismic resistance
and can significantly reduce damage
caused by fault movement (Bray 2001;
Ardah et al. 2018; Chiang et al. 2021).
Based on the numerical results presented
in Figure 3, when the fault movement
increases, it generates a significant
shear force at the bottom of the GRS
structure. However, reinforcement can
effectively impede the development of
the shear zone, thereby preventing the
shear plane from reaching the surface and
causing surface rupture. The reinforcement
reduces the angular distortion by
an average of 60% at the ground surface.
Such reinforced earth mechanism can be
identified as the shear rupture interception
effect. Because of this interception
effect, the intense shear strain develops
horizontally and extends along the bottom
reinforcement layer. The initiated
shear strain reduces with the increased
distance from the fault tip, indicating that
Geosynthetics April/May 2024

Table of Contents for the Digital Edition of Geosynthetics April/May 2024
