The Basics of Soil Compaction
Plus, we’ve included a handy maintenance schedule to help prolong your equipment’s productivity as well as some solid safety best practices. Even the most experienced contractors and machine operators will find this information from our brand name manufacturers, operating manuals, and soil compaction experts to be useful on the jobsite.
What is Soil Compaction?Soil compaction is one of the most critical parts of construction; it’s transforming raw land into a strong engineered support foundation, whether it’s a foundation for a two-car garage, 30-story office building, or a temporary construction road to move heavy equipment. But what is soil compaction?
Soil compaction, through impact force, static weight, or centrifugal force from vibration, reduces the volume of water and air in the soil, resulting in a greater load-bearing soil.
Modern compaction machinery, whether driven or walked behind, is designed to make the soil compaction process as smooth and efficient as possible while still providing operator comfort and safety.
But What is Soil?
Soil can be defined in two ways:
- Any natural material found on the Earth’s surface excluding embedded rock and organic plant and animal material. Based on its particle size, natural soil is divided into four major groups: clay, silt, sand, and gravel.
- Man-made material from using recycled pavement like asphalt or concrete and crushed stone which is then mixed in with various particle sizes to develop compactable material. Some names for crushed stone include traffic bond, crusher run, 57 minus, screenings and tailings.
Why Compact Soil?
Nearly every man-made structure on Earth is built upon and supported by soil.
Before a residential or commercial building is constructed, a foundation must be created, and soil is disturbed from its natural position by excavating, grading, or trenching. When the soil is disturbed, air mixes into the soil mass, and the soil increases in volume. But before this air-filled soil can support a structure over or beside it, the air pockets must be reduced, creating a stronger, denser solid soil mass for a stable, long-lasting foundation.
This is called soil compaction, and it’s done with a variety of specialized compaction equipment.
There are five major long-lasting benefits of this process.
Soil compaction is such an ancient construction technology that during the Roman Empire, roads were built using the compaction of gravel and clay. Centuries later, those roads still exist in modern Italy.
Until just a few decades ago, nearly all soil compaction was limited to large construction sites (roads, hospitals, office complexes, and airports) because only very large, very heavy equipment was available.
With the modern innovation of self-contained portable rammers, forward and reversible vibratory plates, and smaller trench rollers, it became common practice to perform soil compaction in confined areas such as trench backfills, curbs and gutters, bridge supports, slab work, and walkways. Now anywhere soil is moved for construction, the foundation begins with soil compaction.
There are several factors effecting compaction, but the biggest underlying factor is what type of soil is to be compacted and its absorbency. Soil must be tested to determine if it’s suitable for compaction, but more on that later.
How to Compact SoilSpecially designed equipment is used to compact loose soil, whether it’s cohesive soil like clay or granular like gravel, to create a stronger, denser soil. The equipment ranges from hand-operated tampers to extremely large, very heavy rollers. This equipment can be found at jobsites around the world.
There are forces at play along with different types of compaction that can be applied to varying soils or asphalt. Each compaction type uses one of two forces explained in our article “Factors To Consider When Compacting Soil.”