Question

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 3 m and is expected to remain permanently at this new level. Determine the effective vertical stress at depths of 8 and 12 m below ground level:

a) immediately after the rise of the water table

b) several years after the rise of the water table.

Answer #1

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....

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...

A pipe is driven down through a 5m layer of clay (γ = 17 kN/m3)
to an underlying permeable layer. After removing the soil from the
pipe, the water level in the pipe eventually rises to 2m above
ground level. Calculate the pore water pressure in the clay layer
at a depth of 3m below ground level. If the area now becomes
flooded to a depth of 1m, what is the pore water pressure in the
clay layer at a...

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.

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...

A very wide embankment 5 m high is constructed from a fill with
a unit weight of 16 kN/m3 over a saturated sand deposit with the
presence of water table coinciding with its top surface. At a depth
of 3 m below the top surface of the sand deposit, determine the
following: (a) total and effective vertical stresses before
construction of the embankment, (b) increase in vertical stress
induced by the construction of the embankment, and (c) total and
effective...

A 70 m diameter tank will be filled with 9 m of water. The site
consists of 20 m of sand overlying 20 m of clay, overlying another
layer of sand. The water table is located at a depth of 10 m. The
unit weights of the sand layers are 18 kN/m3 and the unit weight of
the clay is 16 kN/m3. Other clay properties are given in Table 1.
Please divide the clay layer into 4 or more sublayers...

3
A wide embankment 5m high is built on the ground described in
the previous example. The material of this bank has a moisture
content of 13% and a dry density of 1860kgm-3. Find the
vertical effective stress in the clay at a depth of 7.33m below the
original ground level.
4
A piezometer tip is set at 10m above datum into the top of a
confined layer of sand. The water level in the piezometer is 40m
above datum;...

A 1.5 m square 0.4 thick footing supports a column load of 350
kN. The underlying soil has a unit weight of 18 kN/m3 and the
ground water table is 2 m below the ground surface. Compute the
change is vertical stress and final vertical stress beneath the
corner of this footing at a depth of 5 m using the 2:1 and
Boussinesq methods. The footing is placed on the ground surface.
Include selfweight of the footing. Discuss the differences...

A group of concrete piles (3×3) is driven into a uniform layer
of medium dense sand, which has a unit weight of gt = A
kN/m3 and a friction angle of f = Bo. The
water table is C m below the ground level. Each pile has a diameter
of 400mm, a length of 10m. The centre-to-centre spacing of the
piles is s = D m.
Assume proper values for A, B, C and D.
Calculate the ultimate vertical capacity...

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