Which type of pile foundation can support a structure primarily through the soil surrounding it?

Friction piles are designed to transfer the load of a structure to the surrounding soil primarily through the friction that develops along the sides of the pile. This type of foundation does not rely on reaching a solid layer at the bottom of the pile, as end-bearing piles do. Instead, the load is supported by the resistance generated from the soil’s friction against the pile’s surface area, making it effective in situations where the load-bearing capacity of the soil is sufficient but the underlying strata may not provide a firm base.

In contrast, end-bearing piles transmit the load directly to a strong layer of soil or rock at the bottom of the pile. Sheet piles are typically used for retaining walls and do not function as load-bearing elements for structures in the same way. Bored piles can provide support through both end bearing and friction, but their primary function can depend on the design and conditions of the surrounding soil. In this context, friction piles are the correct answer due to their ability to rely on the soil surrounding them for support.