Which soil property allows it to be molded into shape and can be a problem if not controlled?

The property that allows soil to be molded into shape is plasticity. Plasticity refers to the ability of soil to deform without breaking when subjected to stress, which is especially evident in clays. This characteristic is crucial in various construction and engineering applications because it allows for flexibility in shaping and compacting soil during earthwork operations.

However, plasticity can present challenges if not controlled appropriately. For instance, soils with high plasticity can lead to issues such as shrink-swell behavior, which can cause instability in structures or foundations. When moisture content changes, highly plastic soils may expand or contract significantly, affecting the integrity and performance of engineered structures. Therefore, understanding and managing plasticity is vital to ensure that soil behaves as expected under load and environmental changes.

This aspect sets plasticity apart from cohesion, which relates to the attractive forces between soil particles; retention, which deals with water-holding capacity; and permeability, which concerns the movement of water through soil. Each of these other properties has its significance in soil mechanics and engineering, but plasticity takes precedence when discussing moldability and related issues.