Movements - Geotechnical Investigation and Design Tables - page 300

Table 23.13 Angular distortion criteria for bridges (Barker at al., 1992, Moulton et al., 1978).

Value of angular distortion Continuous span Single span

0.000 to 0.001 100% 100%

0.001 to 0.003 97% 100%

0.003 to 0.005 92% 100%

0.005 to 0.008 85% 95%

•

A ≤ 0.004 is acceptable for continuous span bridges.

•

A ≤ 0.008 is acceptable for single span bridges.

23.14 Tolerable displacement for slopes and walls
•

The literature is generally vague on tolerable movements.

Table 23.14 Movements just before a slide (data from Skempton
and Hutchinson, 1969).

Type of system Total movement (cm)

Small to large walls 20-40

Medium to large landslides 40-130

23.15 Observed settlements behind excavations
•

The settlements behind a wall depend on the type of soil, and distance from the
excavation face.

•

The table applies to soldier piles or braced sheet piles with cross bracing or tie
backs.

Table 23.15 Observed settlements behind excavations for various soils (Peck, 1969, O'Rouke et al.,
1976).

Type of soil Settlement/maximum Distance from excavation/

depth of excavation (%) maximum depth of excavation (%)

Medium To Dense sands with interbedded stiff clays with average to good workmanship
0.3 0

0.1 1.2

0.0 2.0

Sand and Soft to Hard Clay with average workmanship
1 0
0.5 0.7
0.0 2.5
Very Soft to Soft Clay to a limited depth with construction difficulties
2 0
1 1.2
0.5 2.3
0.0 4.0
Very Soft to Soft Clay to a significant depth below the bottom of excavation