What factor can lead to crumbling of excavation walls?

The correct choice emphasizes the impact of drying wind on excavation walls. When strong winds occur, they can rapidly evaporate moisture from the soil, which may lead to a decrease in soil cohesion and stability. This loss of moisture can weaken the structural integrity of the excavation walls, making them more susceptible to crumbling or collapse. This is particularly critical in excavated areas where the soil is already disturbed and may not have the same natural support structure as it did before excavation.

In contrast, factors like vibration from traffic or heavy rain typically introduce other dynamics affecting wall stability but do not directly result in crumbling due to moisture loss. Improper drainage can also contribute to water accumulation but does not specifically link to drying effects as a leading cause of structural degradation. Understanding these environmental factors is essential for ensuring the integrity of excavation sites.