What is the typical application for an expansion anchor?

An expansion anchor is primarily designed to securely attach to substrate materials in various soil types, making it a versatile choice in construction and installation. The correct answer identifies its typical application as suitable for most soils, with the exception of very dense or non-pliable materials like solid rock or hardpan, where an expansion anchor might not perform optimally due to insufficient space for the anchor to expand and lock into place.

Expansion anchors work by expanding against the sides of the drilled hole when they are tightened. This mechanism requires a certain amount of space and yielding material, which is available in common soils like clay, silt, loam, or even some softer rocky substrates. However, in solid rock or hardpan, the density and hardness limit the effectiveness and usability of these anchors, as there wouldn’t be the necessary expansion capability.

In contrast, while anchors might seem suitable for sandy or muddy soils, those conditions introduce other challenges like instability or displacement rather than reflecting the anchor's typical application range effectively. Thus, the correct answer reflects the optimal use of expansion anchors in various soil types, barring the exceptions where hard substrates would hinder their function.