A holding device with a chain net was used to automate the removal of wave-dissipating blocks, thereby reducing labor. The device has a simple structure composed of a chain net, which hangs from the support frame and forms four meshes. It is lightweight and without a power unit and has been applied to remove wave-dissipating blocks six times.
Shape of wave-dissipating blocks are more than 40. The most difficult block to be removed was shaped like a combination of two anchors. This block tangled strongly with the surrounding blocks as their legs were long.
The author tried to remove a pile of blocks in the model experiment using the holding device with a chain net. It was possible to remove blocks successively through adequate observation of the situation, taking into account the posture change of each block during lifting to eliminate entanglement with the surrounding blocks．
The time required for lifting was 1 min 27 s/block.