# Useful Relationships and Typical Values In Geotechnical Engineering

Articles > Useful Relationships and Typical Values In Geotechnical Engineering

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

emin = 0.38 ~ 0.5

emax = 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

K0,NC = 0.38 ~ 0.5 in sands

K0,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

Cs/Cc = 0.1 ~ 0.2

### Typical Values of Coefficient of Consolidation for Clays

cv = 10-8 to 5 x 10-7 m2/s

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

Ca/Cc = 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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