Infrastructure Projects - Construction Technology
A Practical Guide to Construction Techniques and Practice
Cranes are probably the most graceful and dramatic pieces of construction equipment. People love to stop and watch them lift a piece of steel way up into the air and join it into a building. They are fascinating to watch, but there are many other devices. There's a whole fleet of tools that are commonly used and are necessary on any construction site.
The machine shown here is often called a shovel. It is not a shovel. It is a backhoe. The way a backhoe works, the operator moves the bucket away from him, digs it into the ground and then pulls it towards him. That direction of work defines a backhoe. A shovel works in the opposite direction. The bucket is oriented.180 degrees opposite what is shown and it digs by moving away from the operator. That's a shovel. Chances are you've never seen a shovel on a construction site because it is not typically used. There are applications that make a shovel just the right tool, but more often than not, you're going to see a backhoe.
This particular backhoe is mounted on rubber tires. It's on a highway construction site, which makes it a kind of a linear site. So the equipment really needs to get around and cover a lot of distance. The rubber tires are ideal for that. Because it's on rubber ties, it also has outriggers. For stability, you would put down the outriggers. That would also increase your capacity, if you're digging against some really tough resisting material, the outriggers will help stabilize the machine.
It's another view of the backhoe. Clearly, it pulls the material towards the machine. I included this one because, if you can imagine, a shovel could be working down at that lower elevation where the two laborers are, and it could dig into this stockpile of material. That motion would define it as a shovel. Again, I think they're rarely found on construction sites. They're more associated with mining, where you're digging up against the face of material.
This is a front end loader. A very, very common device. Typically, it will dig into a stockpile of material and then place it into a truck. It's not really an excavating tool. Some other tool will do the excavating. This machine will pick up the loosely stockpiled material and load it into a truck. Many times the bucket is a tilting bucket, which allows the machine to come alongside of a truck and load it from the side. That's very helpful when you're doing this kind of a linear job and you have a confined width. This machine is also on rubber tires. Both this machine and the backhoe before it can also be had mounted on caterpillar tracks.
It didn't take long before some enterprising person combined these features into one device and this tool is generally called a dynahoe. On the left hand side, you see that loading bucket, but they've even improvised with respect to this bucket to make it more versatile. There's a pin here, and jaws and this bucket actually opens and closes. It can use that motion sometimes to pick up a pile of material. Instead of pushing up against it. It may be desirable to open and close the jaws and pick it up that way.
But because of that kind of jaw arrangement, you can pick up a length of soldier pile. You can pick up a piece of timber pile. You can pick up almost anything and move it around and bring it to wherever it's needed. That makes the loading operation much more flexible. The opposite end of the tool is the backhoe arrangement, but in the instance in this photo, it's not being used to dig. It has a hook on it and it's being used as a little crane. It's carrying two lengths of forms. These look like pavement forms and it's going to bring them wherever they are needed. This machine, again, is on rubber tires. I think that is the typical way It is configured. For stability, it has outriggers on one end. On the other end, it can simply plant the loading bucket to the ground. That makes the machine completely stable on both ends.
There's almost an unlimited number of applications for this machine. The digging bucket on the right hand side can be replaced with any number of accessories. Very often you'll see a concrete-breaking hammer mounted on it, in which case it's usually called a hoe ram. There are other devices that can mount on it as well. This is the most capable machine around. Of course, there's a single cab and a single operator getting paid to do that variety of tasks.
When you're doing a highway job, you're likely to find these two pieces of equipment. The machine on the right is a road grader - a very specialized tool used to strike off material with a high degree of accuracy. It eliminates a lot of hand shoveling. It has a very long wheelbase and it has a blade, which I'm just pointing to here, because you’re sort of looking at an end view. It's hard to really see. You can also see the shadow that it's casting. The blade is very wide and it probably can strike off an area about 10 feet wide. This is a perfect tool for fine grading the granular material just below the pavement. When you get it struck off to grade, you compact it with the roller on the left.
This is a fairly small roller, but perfectly appropriate to this kind of work. Rollers come in every size. This is certainly at the small end. There were much heavier machines. which are used to compact layers of fill as you're placing. This is a steel wheel roller, just the right tool to even out the surface of the subgrade. This area looks as if it's ready for forms to be placed and the concrete roadway to be poured.
I'm going to show you a video now for a pile driver, another very important piece of equipment. In this case, the piles are being driven for the foundation for a building. They can also be driven for soldier piles and lagging. This is a tool you have seen, I'm sure. I'm also sure you've heard this tool, because it has a kind of particular sound made by the drop-hammer striking the pile.