Recommended Values of Bond Strength
The table is based on field and laboratory tests.
Bond strength: Classic drilled nails
qs,k [kPa]1) according to EA Pfähle | ||||||||
Cohesionless soils | Cohesive soils | Rocks | ||||||
qc 2) [MN/m2] | cu 3) [kN/m2] | qu,k 4) [MN/m2] | ||||||
7.5 | 15 | 25 | 60 | 150 | 250 | 0.5 | 5 | 20 |
55 -80 | 105 - 140 | 130 -170 | 30 - 40 | 50 -65 | 65 - 85 | 70 - 250 | 500 -1000 | 500 - 2000 |
Notes:
1) Determination of bond strength should be part of the geological survey
2) Cone resistance, CPT test (according to DIN EN ISO 22476-1)
3) Total cohesion of the soil
4) Uniaxial compression strength
Literature:
EA-Pfähle, ISBN: 978-3-433-03005-9
Values in the table based on soil and rock classification.
Estimated bond strength of soil nails in soil and rock (source: Elias a Juran, 1991)
Material | Construction method | Soil / rock type | Ultimate bond strength qs [kPa] |
Rock | Rotary drilled | Marl / limestone | 300 - 400 |
Phyllite | 100 - 300 | ||
Chalk | 500 - 600 | ||
Soft dolomite | 400 - 600 | ||
Fissured dolomite | 600 - 1000 | ||
Weathered sandstone | 200 - 300 | ||
Weathered shale | 100 - 150 | ||
Weathered schist | 100 - 175 | ||
Basalt | 500 - 600 | ||
Slate / hard shale | 300 - 400 | ||
Cohesionless soils | Rotary drilled | Sand / gravel | 100 - 180 |
Silty sand | 100 - 150 | ||
Silt | 40 - 120 | ||
Piedmont residual | 40 - 120 | ||
Fine colluvium | 75 - 150 | ||
Driven casing | Sand / gravel -low overburden -high overburden | 190 - 240 280 - 430 | |
Dense moraine | 380 - 480 | ||
Colluvium | 100 - 180 | ||
Augered | Silty sand fill | 20 - 40 | |
Silty fine sand | 55 - 90 | ||
Silty clayey sand | 60 - 140 | ||
Jet grouted | Sand | 380 | |
Sand gravel | 700 | ||
Fine - grained soils | Rotary drilled | Silty clay | 35 - 50 |
Driven casing | Clayey silt | 90 - 140 | |
Augered | Loess | 25 - 75 | |
Soft clay | 20 - 30 | ||
Stiff clay | 40 - 60 | ||
Stiff clayey silt | 40 - 100 | ||
Calcareous sandy clay | 90 - 140 |
Note: Convert values in kPa to psf by multiplying by 20.9. Convert values in kPa to psi by multiplying by 0.145.