compressibility and settlement Flashcards
__________ is one of the aspects that control the design of structures.
Settlement
*A steel rod ____________ when it is subjected to tensile stress, and
a concrete column __________when a compressive load is applied.
lengthens
shortens
_______________ are responsible for
settlement of the structure.
Compressive strains
*What distinguish soils from other civil engineering materials is
the fact that the deformation of soils is _________________
(i.e. permanent)
largely unrecoverable
soils are often referred to as a ___________
material or system
In the case the applied load caused shearing stresses to develop
within the soil mass which are greater than the shear strength of
the material, then the soil fails by sliding downward and
laterally, and the structure settle and may tip of vertical
alignment. This is what we referred to as ______________
BEARING
CAPACITY.
settlements of a structure resting on soil may be caused by two distinct kinds of action within the foundation soils namely,
settlement due to shear stress ( distortion settlement)
settlement due to compressive stress (volumetric settlement)
Takes place during or
immediately after the construction of the structure. It is also
known as the distortion settlement as it is due to distortions
within foundation soil.
1.Immediate settlement (Si):
Occurs due to
gradual expulsion of water from the voids at the soil. It is
determined using Terzaghi’s theory of consolidation.
2.Primary Consolidation settlement (Sc):
Occurs after
completion of the primary consolidation. The secondary
consolidation is non-significant for inorganic soils.
3.Secondary consolidation settlement (Ss):
Due to the nonhomogeneous nature
of soil deposits, the magnitude of E
may vary with depth.For that reason,
Bowles (1987) recommended using a
________________ of E
s
nonhomogeneous
weighted average value
_______________ soil
Whose present effective
overburden pressure is the
maximum pressure that the
soil was subjected to in the
past condition.
The current effective stress σ’
is equal σ’p
Normally consolidated soil
Whose present effective overburden
pressure is less than that which the soil
experienced in the past.
over consolidated soil
A soil is said to be _____________if it
had been subjected in the past to a
pressure in excess of the present
pressure.
over consolidated
It is the maximum effective stress
experienced by a soil in its stress
history (past existence)
Pre-consolidation Pressure
there are few methods available in determining the pre-consolidation pressure but most engineers use the ___________________________
casagrande graphical procedure
It is the defined as the ratio of pre-consolidation pressure to the
present vertical effective stress
Overconsolidation Ratio
It is the slope of the normal consolidation line in a plot of void ratio-
logarithm of effective stress
Coefficient of compression/compression index
It is the average slope of the unloading/reloading curves in e –
log ́ plot
Swelling index (Cs)
It is the slope of the void ratio versus effective stress for a
given stress increase Δσ ́ in void ratio versus effective stress p
Coefficient of Compressibility (av)
It is the ratio of change in volume of a soil per unit initial volume
due to unit increase in effective stress
Coefficient ofVolume Compressibility (mv)
