Movements - Geotechnical Investigation and Design Tables - page 302

23.19 Allowable rut depths
•

The allowable rut depth depends on the type of road.

•

The allowable rut depth is a serviceability criterion and does not correspond to
actual failure of a base course or subgrade material.

Table 23.19 Typical allowable rut depths (QMRD, 1981: AASHTO, 1993).

Type of road Paving Allowable rut depth

Haul type Unpaved 100 mm

Access Unpaved 75 mm

Low volume Unpaved 30 to 70 mm

Paved 20to50mm

Major roads Paved 10 to 30 mm

23.20 Levels of rutting for various road functions
•

The rutting criteria are based on the design speed of the road to ensure the safety
of road users.

Table 23.20 Indicative investigation levels of rutting (Austroads, 2004).

Road function Speed Percentage or road length with

rut depth exceeding 20 mm

Freeways and other high class facilities 10%

Highways and main roads 100 km/h 10%

Highways and main roads

≤ 80 km/h

20%

Other local roads (sealed) 60 km/h 30%

•

Rut measured with a 1.2 metre straight edge.

23.21 Free surface movements for light buildings
•

Australian Standards (AS2870) is based on a free surface movement (y s ) calculated
from the shrink - swell index test (I ss ), the depth of active and cracked zone and
the soil suction.

Table 23.21 Free surface movements for light buildings.

Class Site classification Surface movement (y s , mm)

A Competent rock

S Slight 20

<

M Moderate 20 to 40

H High 40 to 60

E Extreme 60

>

P Problem