Vertical stresses 1

Question 1

_________ along a given cross section
of the soil profile is key to analyzing the
compressibility of soils, bearing capacity of
foundations, stability of embankments and
lateral earth pressure on earth retaining
structures.

Answer 1

Nature of stresses

Question 2

______ is a multi phase system

Answer 2

Soil

Question 3

To perform any kind of analysis - we must understand
_________

Answer 3

stress distribution

Question 4

Due to the self
weight of the soil mass.

Answer 4

Geostatic Stresses

Question 5

From structures

Answer 5

Excess Stresses

Question 6

___________- stresses increase with
depth

Answer 6

Vertical geostatic

Question 7

3 types of
geostatic stresses

Answer 7

a Total Stress,
b. Effective Stress,
c Pore Water Pressure, u

Question 8

The rate of drainage depends on the _________ of the soil.

Answer 8

permeability

Question 9

The strength and compressibility of the soil depend on the _________ within the solid
granular fabric. These are called _______.

Answer 9

stresses, effective stresses

Question 10

is the stress applied to the soil by its own
weight

Answer 10

Effective Stress

Question 11

soil carries the stress in 2 ways

Answer 11

• A portion is carried by the water (acts equally in all directions)
• A portion is carried by the soil solids at their point of contact.

Question 12

The sum of the vert. components of the forces at their
points of contact per unit of X- sectional area is the
________

Answer 12

effective stress

Question 13

_________ controls the deformation of the soil

Answer 13

Effective stress

Question 14

The interaction between soils and percolating water has an
important influence on:

Answer 14

The design of foundations and earth slopes,

The quantity of water that will be lost by percolation through a
dam or its subsoil.

Question 15

As water flows through soil it exerts a frictional drag on the soil
particles resulting in head losses. The frictional drag is called
_________ in soil mechanics

Answer 15

seepage force

Question 16

It is often convenient to define seepage as the________

Answer 16

seepage force per
unit volume

Question 17

If the seepage direction is downwards, then the resultant seepage
stresses are in the same direction as the gravitational effective
stresses. T or F

Answer 17

T

Question 18

Foundation failures due to ‘__________’ are
quite common.

Answer 18

piping

Question 19

_______ is a phenomenon by which the
soil on the downstream sides of some
hydraulic structures get lifted up due
to excess pressure of water.

Answer 19

Piping

Question 20

The pressure that is exerted on the soil due to the seepage of water is called the ____________.

Answer 20

seepage force or pressure

Question 21

_______ of soils are reduced due
to the development of neutral stress or pore pressures.

Answer 21

Shear strengths

Question 22

In the stability of slopes, the _______ is a very
important factor.

Answer 22

seepage force

Question 23

A detailed understanding of the _________ is
therefore essential for a satisfactory design of structures.

Answer 23

hydraulic conditions

Question 24

The computation of seepage loss under or through a dam,
the uplift pressures caused by the water on the base of a
concrete dam and the effect of seepage on the stability of
earth slopes can be studied by _________.

Answer 24

constructing flow nets

Question 25

At any depth z, zy_b is the pressure of the submerged soil acting downward and izy_b is the seepage pressure acting upward. T or F

Answer 25

T

Question 26

equal to the ratio of the submerged unit weight of soil and the unit weight of water.

Answer 26

Maximum value of hydraulic gradient

Question 27

________ soils lose all of their shear strength and bearing capacity and a visible agitation of soil grains is observed. This phenomenon is known as __________

Answer 27

cohesion less, boiling or a quick sand condition

Question 28

For all practical purposes the specific gravity of granular materials can be assumed as equal to ______

Answer 28

2.65

Question 29

__________ are common in excavations below the ground water table. This can be prevented by lowering the ground water elevation by _______ before excavation.

Answer 29

Quick conditions, pumping

Question 30

Quick conditions occur most often in__________ and cannot occur in coarse soils.

Answer 30

fine sands or silts

Question 31

The larger the particle size, the lesser is the porosity. T or F

Answer 31

F, greater

Question 32

§ Zone between the land surface and water table § Pore contains water and air § Also called as __________

Answer 32

Unsaturated zone, vadose zone or the zone of aeration

Question 33

§ pores are completely filled with water § Contains water at greater than atmospheric pressure § Also called ________-

Answer 33

Saturated zone, phreatic zone

Question 34

§ Surface where the pore water pressure is atmospheric § Divide between saturated and unsaturated zone

Answer 34

Water table

Question 35

Zone immediately above the water table that gets saturated by capillary forces

Answer 35

Zone Capillary Rise/Fringe

Question 36

Soil Water Three categories

Answer 36

1. Hygroscopic water 2. Capillary water 3. Gravity water

Question 37

· Microscopic film of water surrounding soil particles · Strong molecular attraction; water cannot be removed by natural forces · Adhesive forces (>31 bars and up to 10,000 bars!)

Answer 37

Hygroscopic water

Question 38

· Water held by cohesive forces between films of hygroscopic water · Can be removed by air drying or plant absorption · Plants extract capillary water until the soil capillary force is equal to the extractive force – Wilting point: soil capillary force > plant extractive force

Answer 38

Capillary water

Question 39

· Water that moves through the soil by the force of gravity

Answer 39

Gravity water

Question 40

Amount of water held in the soil after excess water has drained is called the field capacity of the soil.

Answer 40

Field capacity

Question 41

Below the water table, pore pressures are ______. In dry soil, the pore pressure is _____. Above the water table, when the soil is saturated, pore pressure will be _______

Answer 41

positive, zero, negative

Question 42

The height above the water table to which the soil is saturated is called the __________

Answer 42

capillary rise

Question 43

Capillary rise · in coarse soils capillary rise is very small · in silts it may be up to _____ · in clays it can be over ______

Answer 43

2m, 20m