One of the things that I am currently not happy about is the fact that outside forces can draw me into opinions about war. Engineering was initially used for war machines but along the lines of beating swords into plowshares, there have been non aggressive use of the technologies developed. But usually only after it has been dipped in blood. So I try very hard not to get involved in the development of any technology that can be used to inflict pain or worse on another. That is not the reason why I learned engineering.
That being said, I am submersed in the reality of daily overhead rockets and the threat that armed militants will crawl through tunnels and wreak havoc on the civilian population. Judging from what I hear and see around me, the threat is very real.
So while I am not interested in joining an attack I am interested in stopping one. Specifically in finding all the tunnels that they have been digging and risking less in the process. I am certain that probably has done this calculation, but if they have, I can’t understand why they haven’t acted on it.
There are about 60 km of border between us and Gaza. If we drill holes spaced evenly say every 6 m, then the following is about right:
| total linear distance m | 60000 |
| distance between holes m | 6 |
| total number | 10000 |
| hole depth m | 100 |
| total drilling m | 1000000 |
| total cost $ | 10000000 |
| in millions $ | 10 |
| speed m/hr | 40 |
| machine hours | 25000 |
| time to completion weeks | 26 |
| hours to completion | 2600 |
| machines needed | 9.615385 |
So 10 machines, 6 months and 10 million $ should reveal all the tunnels that are within 100 m of the surface. Seems reasonable, since I am quite certain that it is a negligible amount compared to the daily cost of the war in money and lives.
Obviously there are specific areas that are direct lines to inhabited areas that would be logical starting points, and we could go deeper and denser there.
It is likely that contact with a tunnel would be noticed in the drilling phase, but if not, sound sensors hung in the holes and then insulated from sound above would be an effective detection of underground activity.
Once detected, seawater can be pumped into the hole. I’ve heard that they stretch for several kilometers. If the section area of the hole is 1m by 3m (a conservative estimate) then the amount of water needed would be 3000 m^3 / km. At 2000 l/s that’s 7200 m^3 per hour. So if you have more than half an hour, you could probably go for a cheaper pump. Although looking for water spewing out of houses could be easily detected. And perhaps a sufficient solution, alternative to explosives.
Order or Chaos 