Failure Reason 3: Poor Drainage and Compaction

What happens here

The third critical oversight leading to retaining wall failure is the lack of sufficient drainage aggregate behind the wall and improper compaction. When the ground behind the wall settles (due to improper compaction), water can become trapped, creating hydrostatic pressure against the wall. Instead of weeping evenly through the wall's face, the trapped water builds pressure, causing the wall to 'belly out' and eventually blow out. The presenter points out the settled grade behind a failed wall, illustrating the problem.

Goal: Explain how lack of drainage aggregate and improper compaction lead to hydrostatic pressure and wall blowouts.