Retaining walls - Geotechnical Investigation and Design Tables - page 263

Table 20.19 Typical details of nails and facings.

Design consideration Wall type

Soil nailed wall Tieback anchored walls

Prestressing load Nominal Significant

Nuts Torque to 20 kN load vertical Torque to 150 kN to 400 kN typically

system, reducing to 5 kN at 70 ◦
slope. In some cases a bent bar
may be used instead of plates

Bondage Along entire length Over free length

Typical length 0.5 to 1.5 slope height Long - to competent strata at depth

Typical inclination 10 to 15 ◦ to horizontal 20 to 30 ◦ to horizontal

Typical plates 150-250 mm square, 200 mm to 300 mm square,

15 mm to 20 mm thick 20 to 25 mm thick

Grade 43 Steel Grade 43 steel

Anchorage 24 to 36 mm diameter Strands or specialist bars with plate

Typical shotcrete face 150 mm to 250 mm 200 mm to 300 mm

•

Table below is for wall anchor inclined at 15 ◦ to horizontal and with a factor of

safety of 1.5.
- Groundwater condition is for a flat top
-

Table based on:

Soil cohesion of 10 kPa.

Soil Unit Weight of 18 kN/m 3 .

Table 20.20 Typical anchor loads (Taken from graphs in Ortiago and Sayao, 2004).

Height of Loading Typical anchor load (kN)

wall (m)

25 ◦ 35 ◦ φ = φ =

3 Horizontal top

+

20 kPa surcharge 50 40

Slope at 30 ◦ behind wall surcharge 120 100 +

Groundwater at 50% wall height surcharge 60 50 +

Groundwater at 100% wall height

+

surcharge 70 70

4 Horizontal top 20 kPa surcharge 80 70

+

Slope at 30 ◦ behind wall surcharge 180 150

+

Groundwater at 50% wall height

+

surcharge 110 90

Groundwater at 100% wall height surcharge 130 130 +

5 Horizontal top 20 kPa Surcharge 130 110

+

Slope at 30 ◦ behind wall surcharge 260 220 +

Groundwater at 50% wall height surcharge 170 150 +

Groundwater at 100% wall height

+

surcharge 200 200

6 Horizontal top 20 kPa surcharge 190 160 +

Slope at 30 ◦ behind wall surcharge 350 300 +

Groundwater at 50% wall height

+

surcharge 240 220

Groundwater at 100% wall height surcharge 280 280

+