There have been reports of the use of drones (flying and ground), sponge bombs, explosives, dogs and bulldozers being used to counter the lengthy Hamas tunnels. There have been videos of Israeli bulldozers digging into the entrances or digging into shallow tunnels.

Whatever is actually being done by the IDF is working fairly well as Israel has lost about 50 soldiers in Gaza operations while eliminating thousands of Hamas.

Here is a review of the different drones and other counter-tunnel technology.

The feasibility of sponge bomb feasibility is supported by known substances like elephant toothpaste. Elephant toothpaste is a foamy substance created by the rapid decomposition of hydrogen peroxide using potassium iodide or yeast and warm water as a catalyst. The reaction proceeds rapidly depending on the concentration of hydrogen peroxide. Youtuber Mark Rober has made large scale elephant and Devil's toothpaste demonstrations. The expanded volume seems to be hundreds of times the original volume of liquid.