Two most common compaction mistakes you should avoid are over compaction and under compaction. They are usually the result of untrained or careless work.
A general idea in our minds is that we can not over compact the soil. As we increase the compaction it will become more and stronger.
But this is not the case. Doing compaction beyond the need would cause the soil particles to break down. It will reduce its support capability due to the separation that happens within the soil mix. This will lead to weakness in soil, not strength.
To make it further clear, you can perceive it like this. Let’s suppose, you have a pile of small rocks and you try to hammer them down into small pieces. You can do it with the correct amount of force.
But, if you keep hammering them down beyond the size of rock you desire, you will end up having them in very small sizes particles like sand, which is completely different than what you wanted
Over compaction breaks down the materials to such extent that their composition is changed.
Under compaction can happen as result of certain mistakes:
- Not using large enough piece of equipment that can handle the job will result in under compaction.
- Not making enough passes with the compactor may also result in under compaction.
Under compaction can cause uneven settlements. Since the soil is not compacted properly, it will not be able to bear the weight above it, which can lead to structural issues.