Hydraulic Structures: Fourth Edition

Table 2.3 Illustrative engineering properties for selected soil types (compare with Table 2.6)Descriptive

Saturated

Shear strength

Coefficient of

Coefficient of

unit weight,

(effective stress)

compressibility, m

v

horizontal

(kN m

3

)

Cohesion

Friction,

(

10

4

m

2 kN

1

)

permeability

c

(kN m

2

)



(degrees)

kh

(m s

1

)

Gravels



0



30–45

10

1

–10

2

Sands

17–22



0



30–45

(0.1–1.0)

10

2

–10

5

Silts

}



5



20–35

}

10

4

–10

6

Clays



0



20–30

Intact clay,

(soft–medium)



10

8

If weathered,

Clays

15–21



10



30

(1.0–10.0)

fissured, or

(sensitive, silty)

with silt lenses

{

10

3

–10

8

Clays



50



20

(medium–stiff )

}}

1. Values of

m

andv

kh

are subject to wide variation; the figures quoted are a guide to the order of magnitude only.

2.

kh



10

4

ms

1

is necessary for good drainage, i.e. for dissipation of excess porewater pressures;

kh



10

8

ms

1

corresponds to being virtually impervious.

3. The properties of coarse-grained soils are controlled by relative density and particle shape; those of clay-type soils are influenced by their nature and

stress history etc.