Geoscience Reference
In-Depth Information
•
Load Transfer Platform (LTP) used to transfer the load on to the pile.
•
Typically LTP thickness
=
500mm with at least 2 No. biaxial geogrids.
•
For geosynthetics used to cap the deep foundations, the allowable strain
<
3% in
long term creep.
•
For low embankments, there may be dynamic effects of loading on ground:
-
2-3m for highways.
-
4-5m for high speed trains.
21.25 Dynamic magnification of loads on piled rafts for
highways and high speed trains
•
The LTP acts as a geosynthetic soil cushion. This reduces the dynamic load on
piles for low embankments.
•
The table provides this dynamic magnification factor for the loads.
Table 21.25
Dynamic magnification factor for dynamic loads on top of piled railway embankment
(Brandl, 2001).
Height of fill
Dynamic magnification factor
Without geosynthetic cushion
With geosynthetic cushion on top of pile caps
H
o
≥
4.0 m
1.0
1.0
H
o
3.0 m
1.5
1.0
≥
H
o
2.0 m
2.5
1.5
≥
H
o
≥
1.5 m
3.0
2.0
H
o
1.0 m
Not applicable
2.5
≥
21.26 Allowable lateral pile loads
•
The allowable lateral pile loads depends on the pile type and deflection.
Table 21.26
Allowable lateral pile loads (USACE, 1993).
Pile type
Considerations
Deflection (mm)
Allowable lateral load (kN)
Timber
No deflection
-
45
Concrete
criteria
-
65
Steel
-
90
Timber
Some deflection
6
40
limitations
12
60
Concrete
6
50
12
75
Timber - 300 mm Free
Deflection
6
7
Timber - 300 mm Fixed
constrained
6
20
Concrete 400 mm - Medium sand
6
30
Concrete 400 mm - Fine sand
6
25
Concrete 400 mm - Clay
6
20
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