Geoscience Reference
In-Depth Information
In North America, several shaking table tests have been conducted on
modular block walls at the Royal Military College (RMC) Canada (e.g., Bathurst
et al., 1997). The shaking table tests conducted at RMC were models of a modular
block wall. The models were 240 cm long, 140 cm wide, and 102 cm high.
Concrete blocks of dimensions 10 cm by 16 cm by 3.4 cm were used. The backfill
soil was a silica sand that has a relative density of 67%. The reinforcement was an
HDPE geogrid. The connection between the blocks was frictional or fixed, where
as the block-geogrid interface was mostly frictional. The input acceleration was
increased in several stages with a frequency of 5 Hz until it reached 0.35 g. The
outward displacement of the facing was compared for four different models that
had different combination of block-block and block-geogrid interfaces.
It has to be noted that because of the size of the shake table facilities,
reduced modular blocks and reinforcements were used. However, these tests
were possibly subject to scale and stress-level effects. Full-scale shaking table
test for a wall above 5m, for example, is almost impossible and not affordable
because of the high cost in addition to lack of availability of test facilities. Japan
has two shake tables that may accommodate a full-scale wall of 5 m and above.
The two shake tables are available at the National Research Institute for Earth
Science and Disaster Prevention (NIED) and the Building Research Institute
(BRI), respectively. This chapter reviews the test results conducted on these two
shake tables. A brief review for the Japan Railway shake table test is also
included. Some general conclusions pertaining to the performance of these walls
are made.
2 REINFORCED EARTH WALL
A full-scale reinforced soil wall, 6 m high, was conducted for the metallic
reinforcement by the Building Research Institute using the shaking table facilities
available at the National Research Institute for Earth Science and Disaster
Prevention (Futaki et al. (1996)). The resonance frequency and response were
determined at several different heights: 2.5m, 3.5 m, 4.5m, and 6.0m. The wall
was designed based on specifications to have a vertical spacing of 1.2m, but the
length of reinforcement was not reported. The wall was constructed inside a
laminar box (or shear box) 3.0 m wide, 9.5 m long, and 6.0m high. The box,
which has a series of frictionless stacked rings of H-frames, eliminates the
boundary effects at the end of the backfill. The grease was used to eliminate side
friction between the wall and backfill.
Standard metallic reinforcements, concrete facing panels, and connections
were used. The backfill soil is a silty sand that has 19% fines. The angle of friction
was 34.4
8
. The dynamic properties of the sand (Young's modulus at small strain
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