Todd Jones of Multiquip has spent the last 25 years resolving soil compaction issues. As the company’s Northwest District Sales Manager, he’s made it his mission to help everyone in this critical area of the industry save time and money by making sure they have the right equipment for their application. His Grandfather, a lifelong general contractor, would often say, "Tell him to go pound sand!" when he was frustrated with someone. And by Todd’s second year of college studying geotechnical engineering, he finally understood exactly what his Grandfather meant. You’ll waste a lot of time and accomplish nothing by trying to pound sand or any granular-type soil! Soil compaction is defined as a method of mechanically increasing the density of soil. Nearly every type of building site and construction project uses mechanical compaction and compaction products.
Proper Compaction Goals
- Increase load-bearing capacity
- Prevent sail settlement
- Make the foundation more stable
- Reduce water seepage, swelling, and contraction
This is officially categorized into 15 groups by the AASHTO (American Association of State Highway and Transportation Officials). But for practical purposes, there are three basic soil groups: Cohesive, Granular, Organic (this soil is not suitable for compaction). Every soil type behaves differently, so each type has its own requirements for compaction methods. A soil’s makeup determines the best compaction method to use. And anyone can determine what type of soil it is by picking it up and trying to roll it into a ball. If it sticks together, it’s cohesive – if it doesn’t, it’s granular.
Clay is cohesive and its particles stick together, so a machine with a high impact force is required to ram the soil and force air out to make sure there are no air voids. A rammer is the best choice, or a pad-foot vibratory roller if higher production is needed.
Since granular soils are not cohesive, and the particles require a shaking or vibratory action to move them, vibratory plates are the best choice.
While it is not soil, it still needs to be compacted. Asphalt is considered granular due to its base of mixed aggregate sizes (crushed stone, gravel, sand and fines) mixed with asphalt. As a result, asphalt must be compacted with pressure and vibration.
Proper Compaction Technique
Lift height (depth of the soil layer) is an important factor that affects machine performance and compaction costs. If the lift is too deep, the machine takes longer to compact the soil and a layer within the lift will not be compacted. Soil can also be over-compacted if the compactor makes too many passes. Over-compaction is like constantly hitting concrete with a sledgehammer. Cracks will eventually appear and reduce density. This is a waste of man-hours and adds unnecessary wear to your equipment.
Jobsites vary, but a basic guideline is:
Single Directions plates, lifts of 6-8” rammers lifts of 10-12”, and reversible plates lifts from 12”+ (use as a guideline only). Jobsite and specification variables need to be considered. Injuries and fatigue can also add significant costs to any job site. Multiquip has integrated high tech Anti Vibration handles into all of our Rammers and Plate Compactors. Anti-vibration handles dramatically reduce operator fatigue and help increase productivity. Todd has personally tested every single type of Multiquip Compactor using various compaction test methods and found that every one of them was able to accomplish 100% compaction results quickly and efficiently by matching the right machine to the type of soil you have. On-site, you might hear people mention machine specifications in terms of operating weight, compaction force, travel speed, and other terminology. In reality, proper technique for the job site conditions and (if necessary) soil testing are more critical to correctly compacting an area than any one specification. Operator comfort using anti-vibration handles, equipment balance and durability play a bigger part in the overall effectiveness of compaction equipment. If you have questions on your job site about the proper equipment selection and technique, call us today. The Most Knowledgeable Pros in Construction Supplies are here to help, working shoulder to shoulder with the experts from the manufacturer like Todd to deliver job site solutions.