What type of concrete pile uses a mandrel to prevent collapse during installation?

Cased piles are indeed the correct answer, as they utilize a mandrel during the installation process to maintain the integrity of the pile and prevent collapse. The mandrel is a temporary casing that provides structural support while the concrete is placed and cured within it. This method is particularly useful in unstable soil conditions, where there is a risk of the pile collapsing or the soil migrating into the pile during installation. By using a mandrel, the installation process can ensure that the dimensions and shape of the pile remain consistent and that the structural integrity is maintained.

Friction piles, end-bearing piles, and precast piles do not require the use of a mandrel in the same way. Friction piles rely on the frictional resistance between the surface of the pile and the surrounding soil to support loads, making the use of a mandrel unnecessary in their installation. End-bearing piles transfer loads directly to a solid strata beneath the soil, and while they may require care in installation, they do not rely on a mandrel for structural support. Precast piles are manufactured off-site and driven into the ground, but their installation does not involve a mandrel to prevent collapse. Each of these alternative types of piles operates under different principles, thus distinguishing cased piles as the