The soil in central and southern Texas swells and contracts when exposed to water. This repeated cycle causes the ground to shift and creates voids beneath your slabs. The heavy slab easily settles into this void, causing cracks and uneven slabs.
Depending on the slab location, the soil beneath the slab could also wash out. Without the support needed, the slab sinks. The process may happen slowly or all at once, but regardless, it’s important to remember it’s the soil beneath the slab that caused the problem, so replacing the slab without addressing the soil is a temporary fix.