Why not?

So far the Israeli security fence seems to be working fairly well. It's unsurprising, therefore, that they're looking for other ideas along the same lines:

The Israeli military is seeking bids for building an 80-foot-deep trench along part of Gaza's border with Egypt that would be intended to block the digging of tunnels used for smuggling arms to Palestinian militants.

Military officials who disclosed the plan on Thursday, after the request for bids was published in newspapers, cautioned that the decision to build the trench was not final and would depend on the financial and engineering details proposed by contractors. But the tentative design suggests that it could be a major undertaking costing millions of dollars.

Sounds like a good idea to me.