This set of Design of RC Structures Multiple Choice Questions & Answers (MCQs) focuses on “Pile Foundation”.
1. Which of the following is not a type of pile based on foundation or the use?
a) End bearing piles
b) Timber piles
c) Compaction piles
d) Anchor piles
View Answer
Explanation: Based on foundation or the use, piles are classified as: End bearing pile, friction pile, compaction pile, tension pile or uplift pile, anchor pile, fender pile and dolphins, batter pile, and sheet pile. The timber pile is classified under type of pile based on material and composition.
2. Which type of pile is used to transfer load through water or soft soil to a suitable bearing stratum?
a) Friction pile
b) Tension pile
c) Sheet pile
d) End bearing pile
View Answer
Explanation: According to the use of pile foundation, end bearing pile foundation is used to transfer load through water or soft soil to a suitable bearing stratum. These piles develop most of the load – bearing capacity at the toe of the pile. This type of pile acts in the same way as column.
3. Which of the following is a type of bored cast – in – situ piles?
a) H – pile
b) Sheet pile
c) Pipe pile
d) Pressure piles
View Answer
Explanation: Piles are classified on the basis of materials and composition. First is concrete piles Which can be both precast and cast – in – situ. Further cast – in – situ are both driven and bored. Bored piles are pressure piles and under – reamed pile.
4. Under – reamed pile is a special type of bored pile.
a) False
b) True
View Answer
Explanation: Under – reamed pile is a special type of bored pile having an increased diameter or bulb at some point in its length. This is done to anchor the foundation in expansive soil subjected to alternative expansion and contraction.
5. Which of the following is the maximum design load for Which precast concrete piles are used?
a) 800 kN
b) 750 kN
c) 850 kN
d) 700 kN
View Answer
Explanation: The precast concrete piles are generally used for a maximum design load of about 800 kN except for large prestressed piles. These must be reinforced to withstand handling stresses. They require space for casting and storage. More time is required to set and cure before the installation. They also require heavy equipment for handling.
6. In Which condition composite piles are used?
a) When the soil is subjected to alternate expansion and contraction
b) When large inclined forces are to be resisted
c) When there is an impact of ship or other floating objects
d) When the upper part of the pile is to project above the water table
View Answer
Explanation: The composite piles are suitable where the upper part of the pile is to project above the water table. Such a pile consists of a lower portion of untreated timber and an upper portion of concrete. These can be made from concrete and timber or concrete and steel.
7. Piles are driven by means of a hammer supported by crane or by pile driver.
a) True
b) False
View Answer
Explanation: The piles are commonly driven by means of a hammer supported by crane or by a special device known as a pile driver. The hammer is guided between two parallel steel members known as leads. The leads are carried such that they can be supported in both vertical and inclined positions.
8. Which of the following cannot be used to determine the load carrying capacity of a pile?
a) Dynamic formulae
b) Penetration tests
c) Double acting hammer
d) Pile load tests
View Answer
Explanation: The load carrying capacity of a pile can be determined by using the methods: Dynamic formulae, static formulae, pile load tests and penetration tests. This depends on the permissible settlement and overall stability of the pile foundation.
9. What is the equation of Engineering News formula for allowable load in case of drop hammers?
a) Qa = WH / [6(S + 2.05)]
b) Qa = WH / [6(S + 2.5)]
c) Qa = WH / [6(S + 0.25)]
d) Qa = WH / [6(S + 0.5)]
View Answer
Explanation: The equation of Engineering News formula for allowable load in case of drop hammers is given by:
Qa = WH / [6(S + 2.5)]
Here (Qa) is allowable load,
(W) is weight of hammer and
(H) is height of fall.
Also (F) is factor of safety Which is equal to: 6,
(C) is empirical constant given by: 2.5 in case of drop hammer.
The final set penetration is denoted by (S). This is usually taken as average penetration, cm per blow for the last 5 blows of drop hammer.
10. Which of the following is used by IS: 2911 (Part II) 1964 based on the expression by Hiley as dynamic formula?
a) Qf = ηh.W.H.ηb / [S + (C / 4)]
b) Qf = ηh.W.H.ηb / [S + (C / 6)]
c) Qf = ηh.W.H.ηb / [S + (C / 2)]
d) Qf = ηh.W.H.ηb / [S + (C / 8)]
View Answer
Explanation: IS: 2911 (Part II) 1964 gives the formula based on an original expression by Hiley as:
Qf = ηh.W.H.ηb / [S + (C / 2)]
Here Qf = ultimate load on pile,
W = weight of hammer (in kg).
Also, H = height of drop of hammer (in cm),
S = penetration or set per blow (in cm) and
C = total elastic compression (C1 + C2 + C3).
The efficiencies are ηh = efficiency of hammer and
ηb = efficiency of hammer blow.
11. The static formulae are based on the assumption that the ultimate bearing capacity Qf of a pile is the sum of the total ultimate skin friction Rf and total ultimate point or ultimate end bearing Rp.
a) False
b) True
View Answer
Explanation: The static formulae are based on the assumption that the ultimate bearing capacity Qf of a pile is the sum of the total ultimate skin friction Rf and total ultimate end bearing Rp. This is given by:
Qf = Rf + Rp or Qf = As rf + Aprp
Here rf is average skin friction and
rp is unit point or the resistance.
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