Negative Skin Friction

Q. The action of negative skin friction on the pile is to

1. Increase the ultimate load on the pile
2. Reduce the allowable load on the pile
3. Maintain the working load on the pile
4. Reduce the settlement of the pile

Q. Negative skin friction in a soil is considered when the pile is constructed through a

1. Filled material
2. Dense coarse sand
3. Over consolidated stiff clay
4. Dense fine sand

Q. Negative skin friction occurs when

1. An upward drag exists in the pile
2. The surrounding soil settles more than the pile
3. The pile passes continuously through a firm soil
4. The driving operation begins

Q. The negative skin friction on a pile develops when:

1. The ground water table rises
2. The soil near the tip is clay
3. The soil in which it is driven is sandy
4. The soil surrounding it settles more than the pile

Q. In the case of a pile foundation, negative skin friction may occur at a load which is

1. lower than the designed load
2. higher than the designed load
3. equal to the designed load
4. of any magnitude

Q. Skin friction capacities of a 40 cm diameter driven concrete pile for the portions A, B and C are 17 kN, 63 kN and 503 kN respectively, and point load capacity is $11000kN/m^2$. Total pile load capacity will be

1. 3743 kN
2. 2864 kN
3. 1965 kN
4. 1529 kN

Q. A pile of $0.50\text{m}$ diameter and of length $10\text{m}$ is embedded in a deposit of clay. The undrained strength parameters of the clay are cohesion $=60{\text{kN/m}}^2$ and the angle of internal friction $=0$. The skin friction capacity (kN) of the pile for an adhesion factor is 0.6, is

1. 671
2. 565
3. 283
4. 106

Q. A single pile, 50 cm in diameter and 15 m long is driven in clay having an average un-confined compressive strength of $100kN/m^2$. The ultimate bearing capacity of the pile, neglecting end bearing, if any, and assuming shear mobilization factor of 0.8 around the pile is

1. 942 kN
2. 1884 kN
3. 1177.5 kN
4. 1334.5 kN

Q. Four columns of a building are to be located within a plot size of $10\text{m}\times 10\text{m}$. The expected load on each column is $4000\text{kN}$. Allowable bearing capacity of soil deposit is $100{\text{kN/m}}^2$. The type of foundation best suited is

1. Isolated footing
2. Raft foundation
3. Pile foundation
4. Combined footing

Q. Identify the two TRUE statements from the following four statements.
I. Negative skin friction is higher on floating piles than on end bearing piles.
II. All other things being the same in footings on sand, the footing with smaller width will have lower settlement at the same net pressure.
Ill. The void ratio of soils is always less than 1.0.
IV. For determining the depth of embedment of anchored sheet piles, net moment at the anchor elevation is set to zero.

1. I & IV
2. I & III
3. I & IV
4. II & III

Q. Consider the following statements regarding negative skin friction in piles:

1. It is developed when the pile is driven through a recently deposited clay layer.
2. It is developed when the pile is driven through a layer of dense sand.
3. It is developed due to sudden drawdown of the water table.

Which of these statements is/are correct?

1. 1 alone
2. 2 alone
3. 2 and 3
4. 1 and 3

Q. Which of the following statements are true for the pile shown in the figure?

1. Frictional resistance acts upwards throughout the length of the pile.
2. Negative skin friction acts over the length AB.
3. Frictional resistance acts upwards over the length BC.
4. There is point resistance at level C.

Select the correct answer using the codes given below:

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

Q. Statement (I) : Negative skin friction will act on the piles of a group in filled-up reclaimed soils or peat soil.

Statement (II) : The filled-up or peat soils are not fully consolidated but start consolildation under their own overburden pressure, developing a drag on the surface of the piles.

1. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
2. Both Statement (I) and Statement (II) are individually true but Statement (I) is not the correct explanation of Statement(I)
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true.

Q. Directions : The following items consists of two statements; one labelled as 'Assertion (A)' and the other as 'Reason (R)'. You are to examine these two statements carefully and select the answers to these items using the codes given below :

Codes:

Assertion (A) : Negative skin friction will act on piles in filled up soil, which should be considered in design of pile foundations.
Reason(R) : The filled up soils start consolidating and develop a drag force on the pile.

1. both A are R are true and R is the correct explanation of A
2. both A and R true but R is not a correct explanation of A
3. A is true but R is false
4. A is false but R is true