Have you ever put a fence post in the ground or watched it done? The method is universal, global and international. Everywhere that I have been, a hole is dug in the ground, the wooden or steel or other post is placed in the hole and a bunch of concrete is poured in.
I have asked dozens of people why concrete is used. They all say that the weight is needed to hold down the post. I don’t know about you, but I have never seen a post or a piece of steel pipe suddenly rise up off the ground as though an anti-gravity machine was pointed at it. So I don’t know why everyone thinks the weight of the concrete is its important attribute.
Actually, the weight of the concrete is of virtually no importance (except where freeze/thaw cycles are frequent). The function of the concrete is to expand the effective diameter of the post so that if it tries to fall over, it pushes against enough dirt to prevent that. The thing holding the post in place is not concrete; it is the dirt that embraces the concrete. A skinny, bare post will be able to move dirt aside if it is pushed over.
What connection does this have to do with ZW? Just this – ZW principles forbid laminating two dissimilar materials together in a manner preventing them from coming apart after use. Concrete and (wood or steel or plastic) are very dissimilar materials. After the wooden post rots or the steel post rusts or when the fence needs to be removed, getting the heavy concrete out of the ground is a major hassle so it may just be abandoned in place. If it is extracted, you are left with a concrete lollypop around a piece of wood or steel. There is no simple way to remove the concrete so the lollypop is either left on the ground for years or put into a dump.
To begin a ZW analysis, we need to go back to the ZW Principles. We ask ourselves if there is a better design for having the post push against a large quantity of dirt without using dissimilar materials? If other materials are used, can they be separated from the post after use and reused many times? As usual, once the ZW Principles are consulted, the answer could hardly be more obvious. Let us make a steel ‘cage’ for the post base that can be attached to the post by some screws but that has flat ears which are securely attached to the cage but are spaced out away from the post to where they can push against a lot of dirt, thus immobilizing the post.These ears would consist of vertical flat plates, buried in the dirt around the post but attached to the central cage by struts or attachments. Some of the ears would be level with the end of the post and the others would be about a half meter higher on the post.
Now, when we install a post, concrete plays no role. We just attach the cage and ears to the bottom of the post, dig a hole wide enough for it all to fit into, place the cage and post assembly in the hole and fill the dirt back in. Naturally we must do some tamping so the dirt goes back in the hole solidly and we can also add water as we fill the dirt back to make sure the dirt compacts well around the ears. One set of ears will be near the bottom of the post and the second set will be closer to ground level, so they form a couple which prevents the post from being pushed over. Likewise, when we want to remove the post, we just dig out the cage and ears, detach the cage from the post by removing the screws, save the cage for another post and save the post if it is still in good condition. Total needless waste? – zero!
I have used this method for a chain link fence and the posts have not budged for years. There is one corner post that is being pulled hard by fencing in two directions ninety degrees apart, yet it stays firmly immobile. I have two posts used for a hammock that make use of the above principle. They are completely immobile also.
Think about it – when a buried flat surface is pushed against dirt, the dirt cannot flow around it and so it resists all movement. But when a round surface pushes against dirt (such as a round concrete plug) the dirt can flow around it. So the new design is not only conservative of materials and a zero waste design par excellence but it should also WORK BETTER! I ask myself why this new design was not universally used, even before the ZW analysis. The answer is clear. Because the FIRST design used was the concrete and first designs are never replaced until there is a crisis. See a discussion of first ideas.
Your homework, class, should you choose to accept it, is to explain how FUNCTION is being reused in this example.
Because I am describing the proper way to prop up a post, I like to call this a PROPER POST PROPPER.