Shear Strength of Soil
A shear force in a soil tends to cause adjacent particles to slide rela-
tive to each other. The shear strength of a soil is a measure of
its resistance to internal sliding.
There are several factors contributing to shear strength. One is
effective stress, the pressure of contact between soil particles.
Another is cohesion, the electro-chemical attraction between the
particles. A third is the angle of friction between the particles.
Shear strength can be described symbolically as:
t
s
f
c
='+ ' f
tan
)
( After Coulomb
Where:
t
f
is the shear stress at failure,
c
'
is the cohesive strength of the soil,
s'
is the effective stress at the shear surface,
f
is the angle of internal friction.
Values for the cohesive strength and angle of internal friction are
found by laboratory analysis. Total stress can be calculated when the
density of the soil and the elevation of the water table are known. It
can also be measured with a total pressure cell.
Note that pore-water pressure has a negative effect on shear strength.
As pore-water pressure increases, effective stress and shear strength are
reduced.
ss
'=
– u
Where:
s'
is effective stress,
s
is total stress, and
u is pore-water pressure.
When
s
and u are known,
t
f
can be calculated. When
t
f
is known,
s
and u become predictors of foundation stability.
Basic Soil Mechanics
Rembco Geotechnical Contractors specializes in
slope stabilization,
soil nail wall,
foundation repair
and support,
grouting,
shoring,
micropile
construction,
rock drilling, and we remediate
sinkholes. We use a
problem-solving approach in the geotechnical portions of buildings, bridges, water plants, sewage plants, tunnels,
installing caisson bottom, and roads. We are experienced in these applications:
micro piles,
sinkhole repair,
permeation and
pressure
grouting,
soil nails,
cement grouting,
chemical grouting,
micropiles,
compaction grouting, and
rock anchors.
Rembco techniques apply when adding new structures: especially
rock anchor,
microfine cement,
soil nailing, and
micropile
installations for foundation support. Our specialties are
soil nails,
rock anchor,
chemical and
compaction grouting,
mini piles,
sinkhole repair,
micropiles, and
soil nailing.
