Useful Relationships and Typical Values In Geotechnical Engineering

Articles > Useful Relationships and Typical Values In Geotechnical Engineering

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In Civil Engineering and more specifically Geotechnical Engineering there are many instances where the values of engineering parameters are cannot be obtained from the testings. Thus, typical values of these parameters will be used. In this article typical values and useful relationships of many important engineering parameters used in Civil Engineering and Geotechnical Engineering are given.

 

See the full table of typical values of cohesive intercept "C" of soils here

See the full table of typical values of friction angle "φ" of soils here

 

Temperature 

C / 100 = (F - 32) / 180 = (K - 273) / 100 = (R - 492) / 180

where
C = Celsius degree
F = Fahrenheit degree
K = Kelvin degree
R = Rankine scale

 

Water Pressure Gradient 

0.1 kgf/cm² / m   =   0.433 psi/ft   =   0.42 psi/m   =   9.81 kPa/m

 

Acceleration of Gravity at Sea Level

9.806 m/s² = 32.174 ft/s²

 

Typical Values of Mass Density of Water

1000 kg/m³  =  1.0 kg/dm³  =  1.0 g/cm³  =  62.4 pcf  =  8.34 lb/gal  =  350 lb/bbl

 

Atmospheric pressure

1 atmosphere = 2116.2166236739 pounds per square foot (psf) = 14.696 pounds per square inch (psi) = 101,325 N/m² (Pa)  (equivalent to 760 mmHg (torr))

 

Typical Values of Mass Density/Unit Weight of Soils

Sands: 115 ~ 135 pcf ( 18 ~ 21 kN/m³ up to 22 kN/m³ with some gravel content)

Clays: 90 ~ 120 pcf (14 ~ 19 kN/m³)

 

Typical Values of Void Ratios of Sands

e_min = 0.38 ~ 0.5

e_max = 0.75 ~ 1.0

 

Degree of Compaction versus Relative Density of Sands

DR (%)	Qualitative assessment of degree of compactness
0 - 15	Very Loose
15 - 35	Loose
35 - 65	Medium
65 - 85	Dense
85 - 100	Very Dense

 

Typical Values of Coefficient of Lateral Earth Pressure at Rest

K_0,NC = 0.38 ~ 0.5 in sands

K_0,NC = 0.5 ~ 0.75 in clays

 

Typical Values of Void Ratios of Clays 

From e = 2 (extremely soft, weak clays) to e = 0.7 (very stiff clays). There are extreme examples of softer clays (with e as high as 5) and stiffer clays.

 

Typical Values of Critical-State Friction Angle 

Silica sands: 28 ~ 36

Clays: 15 ~ 30

 

Typical Values of Residual Friction-Angle in Clays

As low as 5-7 degrees for smectites. For low confining stress levels and/or large sand content it can be as high as critical-state friction angle.

 

Typical Values of Poisson's Ratio

Drained: v = 0.1 ~ 0.3 

Undrained: v = 0.5

 

Typical ranges of specific gravity (Gs) for various soils

Soil Type	Range of Gs
Sand	2.63 - 2.67
Silts	2.65 - 2.70
Clay and silty clay	2.67 - 2.9
Organic soil	less than 2

 

Typical Values of Atterberg Indices

LL = Liquid Limit = 30% ~ 160% for clays

PL = Plastic Limit = 20% ~ 50% 

 

Typical Values of Recompression Index/Compression Index Ratio of Clays

C_s/C_c = 0.1 ~ 0.2 

 

Typical Values of Coefficient of Consolidation for Clays

c_v = 10^-8 to 5 x 10^-7 m²/s

 

Typical Values of Coefficient of Secondary Compression for Shale, Mudstone, Clay, and Peat

C_a/C_c = 0.02 ~ 0.07 (lower values for shale and mudstone; higher values for peat)

 

Typical Values of Hydraulic Conductivity of Soils

Soil	K
Gravel	10-3 to 1 m/s
Sand	10-7 to 10-2 m/s
Silt	10-9 to 10-5 m/s
Clay	10-13 to 10-9 ms

 

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Read also:

• Cohesion Intercept of Soils + Typical Values
• Specific Gravity of Soils
• Solution of Soil Compaction Check Via The Voids Ratio
• Solution of Unit Weight and Its Conversion from Metric Units to SI and US Units.
• Typical truck dimensions for pavement design

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