Spiritual meaning

Spiritually, sand represents the impermanence of the physical life and can
suggest having to approach death or change in some way. The sands of time
is an image much used in poetry and lyricism.

Psychological meanings

Sand in a dream suggests a degree of instability and lack of security.
When sand and sea are seen together we are not feeling particularly
emotionally secure. When the sands are shifting we are probably unable to
decide what we require from life. If we are conscious of the sand in an
hourglass we are aware of time running out; we perhaps need to be certain
we are making best use of our resources.

Common meanings

Sand can represent impermanence. Because they will inevitably be
washed away by the tide, building sand castles in dreams suggests that there
is some doubt about the validity of a project in which we are involved. They
also indicate that the structure we are trying to give to our lives does not
necessarily have permanence and may be an illusion.

You might also like to consult the entries for Beach, Digging / Excavation,
Hourglass and Time.