Which of the following techniques is NOT mentioned in rubble stabilization methods?

The technique referred to as "Filling with sand" is not typically included among the rubble stabilization methods. The primary focus of rubble stabilization involves methods that aim to secure and stabilize the structural integrity of the marine environment, particularly around coral reefs, as they face numerous threats from natural and anthropogenic disturbances.

Frames, cementation, and settlement devices are all methods used to stabilize rubble. Frames can provide physical support to maintain the structure of the reef while allowing for natural sediment buildup. Cementation is a technique that involves using materials like epoxy to bind rubble together, thus reinforcing its stability against currents and waves. Settlement devices may include tools to ensure that newly placed rubble or coral fragments settle correctly within the ecosystem.

Filling with sand, while it could temporarily provide a substrate, does not actively stabilize rubble in a way that supports the long-term health and recovery of coral reef ecosystems, reinforcing why it does not belong in the list of recognized rubble stabilization techniques.