intro to introduction to geotechnical engineering

down to midway through ch 5 slides; should also review old exam

physical/descriptive/non-design/index properties

color

density

size

stiffness

aka compactibility, workability

compressibility

aka deformation properties

atterberg limits

aka consistency limits, defines plasticity. plasticity can affect strength, hydraulic conductivity, etc. (important characteristics)

granular/cohesionless soils

silt, sand, gravel

#4 sieve

4.75 mm, sand divider

#200 sieve

0.075 mm, silt & clay divider. this is where naming convention changes as well

plasticity index

I_p = w_l - w_p

Plasticity Index = Liquid Limit – Plastic Limit

liquidity index

I_l = (w - w_p)/I_p

activity

A = %Clay / %PI

Measure of how much the clay will swell; differentiates types of clay minerology

double layer thickness

K

hydraulic conductivity/water permeability

dielectric constant

stoke’s law

for hydrometer analysis

bank soil

soil before it is excavated from the ground

gamma_d_f

average dry unit weight of fill

gamma_d_c

average dry unit weight of cut (i.e., the bank soil)

S

degree of saturation

Vwater/Vvoids

n

porosity

e/(1+e) = Vv/V

e

void ratio

Vv/Vs

Se =

wG

other useful relations

other useful relations - for S=100%

G

specific gravity

density of material/density of water

w

water content

Ww/Ws * 100%

bulk density

mass of soil divided by its volume; does not default.

dry: M_s / V

moist: M/V

unit weight

a type of specific weight (which are always represented by gamma)

total W of soil / total V of soil (also = rho*g)

defaults to moist

lb/ft³

kN/m³

dry unit weight

weight of solids / total volume = total unit weight/(1+w)

solids unit weight

weight of solids / volume of solids

mass

lbm or kg

weight

lbf or N

unit weight of water

9.81 kN/m³ = 62.4 pcf = Ww/Vw

relative density

relative compaction

“below groundwater level”

always means it’s saturated 100%

“completely dry”

0% saturated

#40 sieve

0.425 mm

ZAV

zero air voids curve

density of water

1 g/cm³