Group Pile in Clay

Q. Efficiency of a pile group is defined as

1. $\frac{Loadcarriedbythelargestpileinthegroup}{Loadcarriedbythesmallestpileinthegroup}$
2. $\frac{Maximumloadcarriedbyapileinthegroup}{Minimumloadcarriedbyapileinthegroup}$
3. $\frac{Minimumloadcarriedbyapileinthegroup}{Maximumloadcarriedbyapileinthegroup}$
4. $\frac{Averageloadcarriedbyapileinthegroup}{Loadcarriedbyasinglepile}$

Q. The group efficiency of pile group

1. Will be always less than $100\%$
2. Will be always greater than $100\%$
3. May be less than $100\%$ or more than $100\%$
4. Will be more than $100\%$ for pile group in cohesion less soils and less than $100\%$ for those in cohesive soils

Q. A group of 16 piles of $10\text{m}$ length and $0.5\text{m}$ diameter is installed in a $10\text{m}$ thick stiff clay layer underlain by rock. The pile-soil adhesion factor is 0.4; average shear strength of soil on the sides is $100\text{kPa}$; undrained shear strength of the soil at the base is also $100\text{kPa}$

Assuming $100\%$ efficiency, the group side resistance is

1. $5026.5\text{kN}$
2. $10000.0\text{kN}$
3. $10053.1\text{kN}$
4. $20106.0\text{kN}$

Q. A group of 24 piles each of diameter 300 mm and 8 m long are arranged in 4 rows at a spacing of 1.0 m c/c. The capacity of each pile is 300kN. The group capacity of the piles is (in kN).

1. 3100
2. 4100
3. 5100
4. 6100

Q. A group of a 16 piles (4 in each row) was installed in a clay deposit shown below. The diameter of each pile is 0.5m and clear spacing between the pile is 0.5 m. The depth of the pile group is 18m.

Group efficiency of pile group will be

1. 60%
2. 75%
3. 90%
4. 92.8%

Q. What is the value of negative skin friction for a group of piles of 30 cm diameter, 5 m long and spaced at 80 cm c/c and having cohesive strength of soil as 25 kN/m${}^2$? (Neglect bottom contribution in bearing capacity)

1. 925 kN
2. 950 kN
3. 975 kN
4. 1000 kN

Q. For the soil profile shown in figure below, the minimum number of precast concrete piles of $300\text{mm}$ diameter required to safely carry the load fo a given factor of safety of 2.5 (assuming $100\%$ efficiency for the pile group) is equal to

1. 10
2. 15
3. 20
4. 25

Q. The load carrying capacity of an individual friction pile is 200 kN. What is the total load carrying capacity of a group of 9 such piles with group efficiency factor of 0.8?

1. 1800 kN
2. 1640 kN
3. 1440 kN
4. 900 kN

Q. What is the ultimate capacity in $\text{kN}$ of the pile group shown in the figure assuming the group to fail as a single block?

1. 921.6
2. 1177.6
3. 2438.6
4. 3481.6

Q. For the $(3\times 3)$ pile group shown in the figure, the settlement of pile group in a normally consolidated clay stratum having properties as shown in the figure, will be

1. $13.20\text{mm}$
2. $12.775\text{mm}$
3. $7.345\text{mm}$
4. None of these

Q. A group of nine piles in a $3\times 3$ square pattern in embedded in a soil strata comprising dense sand underlying recently filled clay layer, as shown in the figure. The perimeter of an individual pile is $126\text{cm}$. The size of pile group is $240\text{cm}\times 240\text{cm}$. The recently filled clay has undrained shear strength of $15\text{kPa}$ and unit weight of $16{\text{kN/m}}^3$.


The negative frictional load in (in kN, up to two decimal places) acting on the pile group is

1. 472.32

Q. For four free standing pile group having arc tan value of 18.3, the efficiency as per Converse Labarre formula, would be

1. 76%
2. 78%
3. 80%
4. 82%

Q. A group of 16 piles of $10\text{m}$ length and $0.5\text{m}$ diameter is installed in a $10\text{m}$ thick stiff clay layer underlain by rock. The pile-soil adhesion factor is 0.4; average shear strength of soil on the sides is $100\text{kPa}$; undrained shear strength of the soil at the base is also $100\text{kPa}$

The base resistance of a single pile is

1. $40.00\text{kN}$
2. $88.35\text{kN}$
3. $100.00\text{kN}$
4. $176.71\text{kN}$

Q. Consider the following statements:

1. Friction piles are also called floating piles
2. Minimum number of piles to qualify as a pile group is three
3. The group efficiency of a pile group may be either less than 100% or more than 100%.

Which of these statements are correct?

1. 1, 2 and 3
2. 1 and 2 only
3. 2 and 3 only
4. 1 and 3 only

Q. Consider the following statements:

1. Piles are provided in groups, which are connected together by a pile cap. The structure rests on top of the pile cap. The pile cap is situated below the ground level.
2. For situations where pile is subjected to upward pull, pedestal piles or under-reamed piles are more suitable type of foundations.

Which of these statements is/are correct?

1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2

Q. Consider the following statements:

1. In case of pile groups in cohesive soil, block failure occurs for smaller spacing between the piles.
2. According to Feld's rule for determining pile group efficiency, the load carrying capacity of each pile is increased by 1/16 owing to the effect of the nearest pile.
3. In medium dense sand, settlement of a pile group is more than settlement of single pile

Which of these statements is/are correct?

1. 1 and 2
2. 1 and 3
3. 2 and 3
4. 1, 2 and 3