Question

SITUATION 2: EFFECTIVE STRESS

An engineer investigates a granular soil deposit, 4 meters
thick, overlaying a 5 meter thick clay. The

water table is present between the interface of the granular soil
and the clay. The moist unit weight

of the sand is 15.6 kN/m3

, while the clay has a saturated unit weight of 17.8 kN/m3

a.) What is the vertical effective stress at the bottom of the clay?

b.) If the water table rises to the level of the soil surface,
what is the effective stress at the bottom

of the clay layer.

c.) If the same soil structure is below a river that is known to
be 3 meters deep, what is the

effective at the bottom of the clay layer?

Answer #1

Calculate the total overburden stress, pore water pressure, and
effective overburden stress at a depth of 12 feet for the given
soil profile. A 2 ft sand layer with total unit weight of 107 pcf
that is overlaying a 14 ft deep saturated clay layer with a total
unit weight of 118 pcf, sitting on the bedrock. The groundwater
table is 2 ft below the ground surface.

At a reclamation site, a 6-m thick sand layer overlies a 5.8-m
thick clay layer, which is underlain by impermeable rock stratum.
The water level is initially 2.5 m above the ground surface. The
saturated unit weights of sand and clay are 19 kN/m3 and 17 kN/m3,
respectively. A 5-m thick layer of fill will be placed on the
original ground surface, and the unit weights of fill are 19 kN/m3
and 20 kN/m3 above and below water table, respectively....

A layer of sand extends from ground level to a depth of 9 m and
overlies a layer of clay, of very low permeability, 6 m thick. The
water table is 6 m below the surface of the sand. The saturated
unit weight of the sand is 19 kN/m3 and that of the clay 20 kN/m3;
the unit weight of the sand above the water table is 16 kN/m3. Over
a short period of time the water table rises by...

A layer of soil consists of 3m thick of moderately dense sand
having water content of 40% and specific gravity of 2.81 which in
turn underlain by dense clay with water content of 56% and a
specific gravity of 1.65. The groundwater table is at the ground
surface.
Sketch this scenario
Obtain an expressive for determining the in-situ vertical stress
at a point 5m
below the ground surface.
Determine the effective unit weight of each soil strata (NB:
refer from...

b)
A sample of moist soil has a mass of 18.18kg and occupies a
total volume of 0.009 m3. When dried in an oven, the dry
mass is 16.13kg. The specific gravity of the soil solids is 2.70.
(Acceleration of gravity, g = 9.81 m/sec2.)
Determine:
Wet density
Dry unit weight
Void ratio
Water content
Degree of saturation
c)
A 4.5 m deep deposit of silty sand lies above a 6 m deep deposit
of gravel. The gravel is underlain...

The soil profile at the bottom of a 10-ft deep lake consists of
3 feet of high plasticity clay (γsat= 118 pcf) above 12 feet of
silty sand (γsat= 124 pcf). Below the silty sand is a 20-ft-thick
layer of poorly graded sand(γsat= 123 pcf). During a drought, the
lake depth reduces to only 5 feet. Calculate the change in total
stress, effective stress, and pore water pressure at the center of
the SP layer due to drought conditions.

Determine the effective stress increase in the soil at a depth
of 4 m below the footing of area 3 x 5 m2 under an axial load of
4500 kN. Also determine the increase in the stress due to a drop of
the water table from originally 1 m below the footing to 5 m below
the footing bottom.
Please help me with this question with graph and calculation
details, thanks.

Q1. Complete the following table, provided for
a sandy soil (Gs =2.65). Accordingly, find the dry unit
weigh of this soil.
Mass (t)
Vol. (m3)
Air
13.46
Water
13.25
Solids
50.00
Total
Q2. A soil specimen has a moisture content of
21%, a void ratio of 0.6, and a specific gravity of 2.7. Determine
the bulk unit weight of this soil.
Q3. If we are dealing with a very soft clay
soil in the site, which field test equipment will...

2: Two meters of fill (=2.04 Mg/m3)
are compacted over a large area of soil (thus 100% of its influence
is felt throughout the depth). Above the compacted fill, a 3*3m
spread footing loaded with 3000 kN is placed. Assume that the
average density of the soil is 1.68 Mg/m3, and the water table is
very deep. Then it is required to (a) compute and plot the profile
of effective vertical stresses at the middles of ten 2m intervals
or...

Using the data in Textbook Problem 8.8:
a. Plot the vertical effective consolidation stress versus void
ratio on both arithmetic and semi-log graphs. For the arithmetic
graph, constrain the vertical axes to 0.55 and 0.95; and the
horizontal to 0 to 1,500 kPa; for the semi-log graph, use the same
vertical axis constraints, but use 10 kPa and 10,000 kPa to ease
interpretation. Plot the data points only, and draw in a smooth
curve by hand. Plot each graph on...

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