You may think that you can't over compact soil- the more compacted it is, the stronger it is, right? Wrong. Like anything, there is a breaking point. Over compaction will cause the soil to break down which reduces its support capability because of the separation that occurs within the soil mix itself.
The general rule for how much a compactor will compact is: for every 1,000 pounds of compaction force, the machine compacts 1 inch of soil. It's important to make sure that you have the right equipment to compact the area and material that you want.
Yes. There is standard proctor test and modified. Modified uses higher total energy and thus reaches a higher DD. If you are using a standard test result for comparison, you may go over 100% of that test's maximum in the field.
Digging or tilling is not recommended in soil that holds its shape when pressed into a ball, as very moist soils are the easiest to compact.
During Compaction
If you make too many passes in a single direction with your compaction equipment you can over compact the soil. Over compaction will actually lower soil density and cause unnecessary wear to the machine. Always check the work surface before beginning soil compaction for dangerous inclines or declines.
Any heavy tilling when the soil is wet is also destructive to soil structure. The soil will become terribly compacted and dry out too fast.
Maximum dry density, along with optimum moisture content, is determined in the laboratory and provides the target for field compaction. 95 percent is often used as a target compaction threshold to ensure that construction projects are erected on a solid platform.
Compacted soil has its density increased and its pore spaces reduced. This has the result of decreasing the ability of water to infiltrate through the soil into the ground. This creates surface runoff that can carry pollution, creates standing water for mosquitoes, and increases flooding.
If field tests on compacted cohesive soil indicate that field compaction pro c e d u res are providing densities of about 95 percent of the maximum density according to the standard Proctor method, or about 90 percent of the maximum density according to the modified Pro c t o r method, compaction is re l a t i vely ...
The current specifications limit lift thickness to 0.20 meters (8 inches) for most soil conditions. However, if granular soils are used and density measurements are being made, a 0.30-meter (12-inch) lift thickness may be allowed. The 8-inch lift limit is by far the most common application on departmental projects.
Moisture in your soil is vital to achieving proper compaction as the water helps slide soil particles together. Not enough moisture might lead to inadequate compaction; too much moisture will leave water-filled voids that weaken the soil's load-bearing ability.
Aeration, digging, and tilling can temporarily treat soil compaction. For a long-term fix, provide the soil with organic matter, cover, keep the soil planted, and have a healthy soil microbiome. Avoid compacting it further, and it will gradually cure itself.
On average, it takes between 5 to 10 years for disturbed or loosened soil to naturally settle and compact. However, consistent water exposure can expedite this settling process. If you install concrete on soil that has been majorly disturbed within the last 5 to 10 years, you run a high risk of your concrete settling.
Hard-packed soil may have been compacted over time due to foot traffic or heavy machinery, making it difficult for grass roots to penetrate and absorb nutrients. To make the hard dirt suitable for growing grass, it is important to aerate the soil to reduce compaction and allow air and water to penetrate.
Most effects of compaction are detrimental to plant growth. However, there are a few exceptions. Slightly compacted soils in a dry year can increase crop yield as discussed earlier. Another exception is the case of iron deficiency in soybeans.
Aerate the Soil
This is the most common and effective method for fixing compacted soil. Aeration involves creating holes in the soil to allow air, water, and nutrients to penetrate deeper layers. There are two main types of aeration: core and spike aeration.
As water builds on the surface, more and more pressure is applied to the soil. For each foot of water, 2.31 pounds per square inch is applied to the soil particles, and over time this can start to cause those void spaces to collapse. That collapse in void space is compaction.
It is not unusual to achieve field densities from 100 percent to 115 percent of Proctor maximum dry density. Geotechnical engineers may determine that due to load-bearing requirements and soil characteristics, compaction density over 100 percent of Proctor is warranted.
Finding the right compaction level for your project
Soil density can be measured using the Proctor compaction test. There are two variations of this procedure – the Standard and Modified Proctor tests (more on that later). Generally, 95% is considered the benchmark for optimal compaction in construction applications.
Confirming the presence of soil compaction can be done by testing the soil hardness. This involves manually pushing a probe through the soil and measuring the distance the probe can be forced into the soil. The general idea is that the deeper the probe goes into the soil, the less compacted the soil.
Tilling your soil too much can cause damage to the soil biology and the soil structure. Tilling excessively can turn your soil into a powdery dust that doesn't hold nutrients well and is void of beneficial biology. So while tilling can be helpful in some instances, you don't want to overdo it.
Planting immediately after tilling is not usually a good idea. Its best to let the soil settle for a day or two, especially if you're planting seedlings. This can allow the seedling roots to take hold better and firmly establish the plants.
Should You Wet the Ground Before Tilling? If the garden soil that you are planning on tilling is too dry, you should consider adding water to it before you till. Less is usually more, but water to a depth of about 4 inches. Let the water penetrate the soil before you begin the tilling process.