Geosynthetics April/May 2024 - 18

Geosynthetics embankment with seismic resilience for highway
Condition of analysis
Factor of
safety
Sliding
External
stability
Overturning
Bearing capacity
Overall stability
Internal
stability
Tensile strength
Pullout resistance
1.21
3.71
1.82
1.42
1.84 (min.)
59.8 (min.)
TABLE 1 The results of stability analyses for
GRS embankment under seismic condition.
for this project: narrow site proximity,
high embankment, significant differential
deformation due to fault movement,
the need for timely repair of possible
earthquake damage, and the government'
policy for sustainable responsibility.
The designer decided to adopt a geosynthetic
reinforced structure in this section
to build a 551.2-foot-long (168-m)
embankment. The slope near Wuniulan
Creek was shaped as a steep slope to
solve the problem of narrow proximity
at the site. In addition, the design of the
GRS embankment could reuse a large
amount of excavated material from the
adjacent No. 3 tunnel near the site. Doing
so dramatically benefited the project by
reducing the output transportation of
Geogrid
warp
Geogrid
weft
0.5m permeable
material
Crisscross pattern Placed
Crisscross pattern Placed
Crisscross pattern Placed
Crisscross pattern Placed
Excavation and Compaction
L, Depends on the roll length of geogrid
Geogrid laid in the warp direction (parall to the highway direction)
Geogrid laid in the weft direction (perpendicular to the highway direction)
FIGURE 7 Design configuration of the GRS foundation (Sinotech Engineering Consultants, Ltd., 2017)
Analysis and design
Stability analysis
The static stability analysis of the GRS
embankment should first consider the
safety of external stability under various
conditions such as normal, seismic and
storm, including sliding, overturning and
bearing capacity. For overall slope stability,
the SLIDE 6.0 program was used to
analyze the safety factor of slope stability.
It is a 2D limit equilibrium program for
evaluating the safety factor or probability
of soil or rock slope stability failure.
It analyzes the stability of slip surfaces
using vertical slice or non-vertical slice
limit equilibrium methods. The internal
stability analysis, including the safety of
geogrid pullout and tensile strength, was
also confirmed. Based on the analyses,
the design scheme and configuration
of the GRS embankment and the effective
embedded length and spacing of the
geogrid were determined.
The seismic coefficient of dynamic
Alternation
of S.S. & Sh
Backfill
Shale
Sandy
mudstone
Shale
GRS, H1=5m@0.5m
GRS, H2=5m@0.5m
GRS, H3=6.5m@0.3m
ø1.5m Pile@2m
Alternation
of S.S. & Sh
Shale
Alternation
of S.S. & Sh
FIGURE 8 The design scheme of the GRS embankment (Sinotech Engineering Consultants, Ltd., 2017)
18
Geosynthetics | April May 2024
analysis was based on the Code for
Seismic Design of Highway Bridges
issued by the Ministry of Transportation
and Communication (MOTC 2018). The
applied horizontal seismic coefficient (kh)
was 0.182, and the vertical seismic coefficient
(kv) was 0.091. The seismic analysis
results are shown in Table 1, indicating
that the designed GRS embankment was
stable under all conditions, and all safety
factor values met the code requirements.
In addition, the analysis also should consider
the emergency backfill to repair the
surface rupture in case of fault movement.
The weight of the additional backfill has
been included in the study to ensure the
safety of the GRS embankment. Detailed
unwanted earth materials and saving
shipping costs. It was also more in line
with the highest principle of energy conservation,
carbon reduction and sustainable
development of the project.
GRS
Soil replacement
Colluvium
Ground water level
Colluvium

Geosynthetics April/May 2024

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