Hi ! So recently I came across this interesting phenomenon that you can break through a strong concrete wall pretty easily by weakening it with certain holes drilled through it, following Hooke's law. I had heard about it before, but have never really thought about it. But now that I am, I became interested in what kind of forces make the wall strong, and how do the holes weaken it? I drew a picture to help understand a tad better: [PLAIN]http://img411.imageshack.us/img411/5872/hookewall.jpg [Broken] I have a small theory, but Im not sure its correct, thus is why Im asking. I figured that above and below the holes, the the stress on the wall is smaller than elsewhere, because below and above the hole the wall isnt "compressed". Making the wall easier to break in those points. Pic: [PLAIN]http://img827.imageshack.us/img827/2638/hookewall2.jpg [Broken] (The red lines indicate a lower stress level, and the green lines are just for illustration that the whole thing forms a certain "X" in a way.) It is also said that drilling these holes compromises the walls load carrying capacity. So Im interested in how certain forces work together there to make this possible. Feel free to annihilate my idea and bring out your own. Im not so much after the math which tells where to drill the holes, but if you can include it, I'd really appreaciate it. Thanks in advance !