DHARM696 GEOTECHNICAL ENGINEERING16.2 Write brief critical notes on the bearing capacity of piles.
(S.V.U.—B.E., (R.R.)—Nov. 1974 and May, 1975)
16.3 Explain the function of pile foundation and show how the bearing capacity of the foundation can
be estimated. (S.V.U.—B.E., (R.R.)—Dec. 1970)
16.4 Explain the basic difference in the bearing capacity computation of shallow and deep founda-
tions. How are skin friction and point resistance of a pile computed?
(S.V.U.—B.E., (R.R.)—Nov. 1973)
16.5 Outline the procedure to determine the bearing capacity of a single driven pile and that of a
group of piles in a thick layer of soft clay. (S.V.U.—B.E., (R.R.)—May, 1971)
16.6 Distinguish between driven and bored piles. Explain why the settlement of a pile foundation
(pile group) will be many times that of a single pile even though the load per pile on both cases is
maintained the same. (S.V.U.—B.Tech., (Part-time)—Sep., 1982)
16.7 Give a method to determine the bearing capacity of a pile in clay soil. What is group effect and
how will you estimate the capacity of a pile group in clay? (S.V.U.—B.E., (R.R.)—May, 1970)
16.8 What are the various methods used for determining the capacity of (i) a driven pile and (ii) a
cast-in-situ pile?
16.9 What is the basis on which the dynamic formulae are derived? Mention two well known dynamic
formulae and explain the symbols involved (S.V.U.—B.E., (N.R.)—Mar., 1966)
16.10 A wood pile of 10 m length is driven by a 1500 kg drop hammer falling through 3 m to a final set
equal to 1.25 cm per blow. Calculate the safe load on the pile using the Engineering News Formula.
(S.V.U.—B.E., (N.R.)—Mar. 1966)
16.11 A precast concrete pile is driven with a 30 kN drop hammer with a free fall of 1.5 m. The average
penetration recorded in the last few blows is 5 mm per blow. Estimate the allowable load on the
pile using the Engineering News Formula.
16.12 What will be the penetration per blow of a pile which must be obtained in driving with a 3 t
steam hammer falling through 1 m allowable load is 25 tonnes?
16.13 A 30 cm diameter pile penetrates a deposit of soft clay 9 m deep and rests on sand. Compute the
skin friction resistance. The clay has a unit cohesion of 0.6 kg/cm^2. Assume an adhesion factor of
0.6 for the clay.
16.14 A square pile 25 cm size penetrates a soft clay with unit cohesion of 75 kN/m^2 for a depth of 18 m
and rests on stiff soil. Determine the capacity of the pile by skin friction. Assume an adhesion
factor of 0.75.
16.15 A 30 cm square pile, 15 m long, is driven in a deposit of medium dense sand (φ = 36°, Nγ = 40 and
Nq = 42). The unit wt. of sand is 15 kN/m^3. What is the allowable load with a factor of safety of 3?
Assume lateral earth pressure coefficient = 0.6.
16.16 A square pile group of 9 piles of 25 cm diameter is arranged with a pile spacing of 1 m. The length
of the piles is 9 m. Unit cohesion of the clay is 75 kN/m^2. Neglecting bearing at the tip of the piles
determine the group capacity. Assume adhesion factor of 0.75.
16.17 Determine the group efficiency of a rectangular group of piles with 4 rows, 3 piles per row, the
uniform pile spacing being 3 times the pile diameter. If the individual pile capacity is 100 kN,
what is the group capacity according to this concept?
16.18 A square pile group of 16 piles passes through a filled up soil of 3 m depth. The pile diameter is
25 cm and pile spacing is 75 cm. If the unit cohesion of the material is 18 kN/m^2 and unit weight
is 15 kN/m^3 , compute the negative skin friction on the group.