Pick up the incorrect statement:a)Negative skin friction occurs when ...
Negative skin friction develops when a soft or loose soil surrounding the pile settles after the pile has been installed.
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Pick up the incorrect statement:a)Negative skin friction occurs when ...
Negative skin friction
Negative skin friction is a phenomenon that occurs in deep foundation systems, such as piles, when the surrounding soil settles. It refers to the downward load imposed on the pile due to the movement of the soil relative to the pile. While the other statements provided are correct, the incorrect statement is option 'B' which states that negative skin friction develops when a dense soil surrounding the pile settles after the pile has been installed.
Explanation
Negative skin friction occurs when there is a relative downward movement between the pile and the surrounding soil. This can happen due to various factors, such as settlement of the soil, consolidation of soft clay, or lateral movement of the soil due to excavation or adjacent construction activities. The settlement of the soil causes the pile to experience an additional downward load, which is known as negative skin friction.
Correct statements:
a) Negative skin friction occurs when the soil layer surrounding a portion of the pile shaft settles more than the pile.
c) Negative skin friction occurs in the soil zone which moves downward relative to the pile.
d) Negative skin friction imposes an extra downward load on the pile.
Incorrect statement:
b) Negative skin friction develops when a dense soil surrounding the pile settles after the pile has been installed.
Explanation of incorrect statement:
The incorrect statement states that negative skin friction develops when a dense soil surrounding the pile settles after the pile has been installed. This is not accurate because negative skin friction occurs when the soil settles more than the pile, regardless of its density. It is not dependent on the density of the soil but rather on the relative movement between the pile and the surrounding soil. Therefore, it is incorrect to state that negative skin friction develops only in dense soils after the pile installation. Negative skin friction can occur in any type of soil as long as there is settlement of the soil relative to the pile.
In conclusion, negative skin friction is a phenomenon that occurs when the soil surrounding the pile settles more than the pile itself. It imposes an additional downward load on the pile and can occur in any type of soil, not just dense soils.