Question

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. Determine the water pressures and effective vertical stresses at the middle of clay layer (i) immediately after the fill is placed, and (ii) many years after the fill is placed

Answer #1

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...

Consider a 20 foot thick saturated clay that has a sand layer
above it and an impermeable rock layer below it. The clay layer has
an initial effective stress at its midpoint of 3145
lbs/ft2. Due to the presence of a
large water tank on the surface, the stress is increased by 710
lbs/ft2 at the midpoint of the clay layer. How much
total settlement from primary consolidation is expected? Provide
your answer in inches.
Soil properties: Compression index = .324,...

A 10 m layer of sand overlies a 6 m layer of saturated clay,
below which there is impermeable rock. For the clay, cv = 4.4
m2/yr. The ultimate consolidation settlement for a given surface
loading was determined to be sc = 18 cm.
a) How long will it take for 95% of the consolidation settlement
to be completed?
b) What will be the magnitude of settlement 1 year after the
load is applied?
c) How long will it take...

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...

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...

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...

A raft foundation 60 m x 40 m carrying a net pressure of 145
KN/m2 is located at a depth of 4.5 m below the surface
in a deposit of dense sandy gravel 22 m deep: the water table is at
a depth of 7 m. Below the sandy gravel is a layer of clay 5 m thick
which, in turn, is underlain by dense sand. The value of
mv for the clay is 0.22 m2/MN. Determine the
settlement below...

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 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...

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