What effect do freeze-thaw cycles have on earthworks?

Freeze-thaw cycles have a significant impact on soil behavior, primarily causing soil expansion and contraction. When temperatures drop, moisture within the soil can freeze, leading to expansion. Upon thawing, the moisture melts, and the soil contracts. This repeated cycle of freezing and thawing can generate stress within the soil structure, impacting its integrity and performance. Over time, these cycles may contribute to the development of frost heave, which can disrupt the surface of the earthwork and lead to various issues such as cracking and instability.

The other choices do not accurately reflect the effects of freeze-thaw cycles. For instance, rather than enhancing soil stability and strength, these cycles typically create challenges for maintaining stability. They do not inherently increase moisture retention, as freezing and thawing can lead to the loss of moisture due to thawing and drainage. Lastly, while freeze-thaw cycles may affect the soil composition and structure, they generally do not decrease the risk of landslides; in fact, they can often lead to increased susceptibility to such events as soil stability is compromised.