Retaining walls - Geotechnical Investigation and Design Tables - page 256

•

For wall lengths 100m, then 200mm and 150mm perforated pipes are typi-

cally required for walls

>

≥ 5m, and < 5m respectively. Refer Chapter 15 for added

details.

20.7 Minimum wall embedment depths for reinforced
soil structures

•

A minimum embedment of 0.5m should be provided to allow for shrinkage and
swelling potential of foundation soils, global stability and seismic activity.

•

Embedment deepening is required to allow for scour or future trenching. Typically
0.5m or 10% of H, whichever is greater. Reduced embedment may occur where
a high level competent rock is at the surface.

•

The table provides the minimum embedment depth at the front of the wall.

- For a slope in front of wall a horizontal distance of 1m minimum, shall be

provided to the front of the wall and deepen as required.

Table 20.7 Minimum embedment for reinforced soil structures (Holtz et al. 1995).

Slope in front of wall Minimum embedment (m)

Horizontal
- Walls H/20

- Abutments H/10

1V: 3H H/10

1V: 2H H/7

2V: 3H H/5

20.8 Reinforced soil wall design parameters
•

Reinforced soil walls (RSW) are constrained at the top resulting in an increased
earth pressure.

•

The earth pressure tends towards the at rest condition at the surface top, and
decreases linearly to the active condition at 6m depth.

•

The earth pressure at the top depends on the soil reinforcement. Rigid inclusions
move less, with a resulting higher earth pressure.

Table 20.8 Variation of earth pressure with depth of wall (TRB, 1995).

Earth pressure Type of reinforcement with friction angle

coefficient with
depth

Geotextile Geogrid Metal strip Wire mesh

2/3 ¾

φ φ φ φ

0 m (surface) K a 1.5 K a 2.0 K a 3.0 K a

6m K a K a K a 1.5 K a ≥