465 October-2019 Time-Three hours (Maximum marks: 75) Part-A 1. DEFINE VOID RATIO AND POROSITY. Void ratio: The void ratio of a mixture is the ratio of the volume of voids to volume of solids. Porosity: The porosity is the ratio of V S is the volume of solids to V T is the total or bulk volume. 2. DEFINE DARCYS LAW Darcy's law states that the rate of fluid flow through porous medium is proportional to the potential energy gradient within that fluid. The constant of proportionality is the Darcy's permeability of soil. Darcy's permeability is a property of both porous medium and the fluid moving through the porous medium. 3. WHAT IS O.M.C Optimum moisture content (OMC) is the percentage of water present in soil mass at which a specific compaction force can dry
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465 October-2019 Time-Three hours Part-A 1. DEFINE VOID ...6. DIFFERENT TYPES OF SHALLOW FOUNDATION Strip footing Spread or isolated footing Combined footing Strap or cantilever footing
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465
October-2019
Time-Three hours
(Maximum marks: 75)
Part-A
1. DEFINE VOID RATIO AND POROSITY.
Void ratio:
The void ratio of a mixture is the ratio of the volume of voids to
volume of solids.
Porosity:
The porosity is the ratio of VS is the volume of solids to VT is the total
or bulk volume.
2. DEFINE DARCYS LAW
Darcy's law states that the rate of fluid flow through porous medium is
proportional to the potential energy gradient within that fluid.
The constant of proportionality is the Darcy's permeability of soil.
Darcy's permeability is a property of both porous medium and the
fluid moving through the porous medium.
3. WHAT IS O.M.C
Optimum moisture content (OMC) is the percentage of water present
in soil mass at which a specific compaction force can dry
the soil mass to its maximum dry weight. ... For different types
of soils, OMC and maximum dry density curves are different.
4. WHAT IS EFFECTIVE STRESS
Effective stress is the force at contact particles of soil but divided by
total area. The contact area is very less between the particles here.
It cannot be obtained practically but we can calculate the effective
stress by measuring total stress and pore water pressure.
5. DEFINE SAFE BEARING CAPACITY OF SOIL
Bearing capacity is the capacity of soil to support the loads applied to
the ground.
Ultimate bearing capacity is the theoretical maximum pressure which
can be supported without failure; allowable bearing capacity is
the ultimate bearing capacity divided by a factor of safety is known as
safe bearing capacity of soil.
6. DIFFERENT TYPES OF SHALLOW FOUNDATION
Strip footing
Spread or isolated footing
Combined footing
Strap or cantilever footing Mat or raft Foundation
7. WHAT ARE THE FORCES ACTING ON THE TRANSMISSION
LINE TOWER
Shearing force
Bering force
Uplift pressure
Seapage pressure
8. WHAT IS SOIL EXPLORATION
Soil exploration consists of determining the profile of the
natural soil deposits at the site, taking the soil samples and
determining the engineering properties of soils using laboratory tests
as well as in-situ testing methods.
PART-B
9. Define plasticity index and liquidity index.
Plasticity Index
It is the difference between the liquid limit and plastic limit of the soil.
It shows volume of range of moisture content at which the soil
remains in plastic condition.
PI=LL - PL
Here,
PI - plasticity index,
LL - liquid limit
PL - plastic limit
LiquidityIndex
The relative consistency of a fine grained soil in the original state can
be defined by a proportion called as liquidity index.
LI=(W-PL)/(LL-PL)
Here,
LI - liquidity index,
w -sample water content,
PL -plastic limit
LL- liquid limit.
10. Explain the Mohr-coulomb failure theory
Material fails essentially by shear.
The critical shear stress causing failure depends upon the properties
of the material as well as on normal stress on the failure plane.
The ultimate strength of the material is determined by the stresses on
the potential failure plane (or plane of shear)
When the material is subjected to three dimensional principal stress
(i.e.1, 2, 3) the intermediate principal stress does not have any
influence on the strength of material.
In other words, the failure criterion is independent of the intermediate
principal stress.
The theory can be expressed algebraically by the equation.
f s F()
Where
f =s= shear stress on failure plane,
F () = function of normal stress
11. Brief notes on Quick sand condition.
Quick sand condition or boiling Quick sand condition is a condition of
flow, not a type of soil, in which a vertical upward seepage flow causes
floating condition of a particle in cohesion less soil such as Sand and fine
grave.
Where the effective pressure becomes zero.
12. What are the factors affecting the bearing capacity of the soil?
soil strength
foundation width
foundation depth,
soil weight and surcharge,
spacing between foundations.
These factors are related to the loads exerted on the soil and considerably
affect the bearing capacity
13. Mention any six uses of pile.
If a high groundwater table exists beneath the structure.
If the superstructure load is high and non-uniform.
If highly compressible soil is present at shallow depth.
If the structure is located near the river bed or sea shore etc, pile
foundation is suggested to secure the structure form the possible
scouring.
If a canal or deep drainage systems pass near the structure, pile
foundation is suggested.
If soil condition is very poor and it is not possible to excavate the soil up
to the desired depth.
If it becomes impossible to keep the foundation trenches dry by any
measure due to heavy inflow of seepage
14. Define swelling potentials, swelling pressure and free swell.
swelling potentials
Soil swelling is a term generally applied to the ability of a soil to undergo
large changes in volume due to increased moisture content