After WWII, Italy was facing a crisis. Cultural monuments, like the Ponte Vecchio bridge and the Pepoli Museum, had been damaged by settlement and the Allied bombings. The country needed an underpinning method to save the failing foundations of its historic structures.
Using the foundation technology of the time would be a challenge—it would require heavy, building-disturbing, equipment. There was no way to do the work without causing the fragile structures even greater harm.
The structures were in disrepair until the 1950s, when Dr. Fernando Lizzi emerged with a solution—a non-invasive, drilled support called micropiles.
A Fresh Answer to Traditional Piling Problems
In the years that followed, micropile technology expanded and spread from country to country, gaining recognition as it was put to use worldwide.
What convinces contractors to adopt the new micropile technology? What are the advantages over traditional piling methods, such as driven or cast in-place piles?
Versatility, within limited workspace
A micropile contractor can adapt their installation equipment to suit the environment they’re working in. Some micropile equipment fits in just eight feet of headroom, making it perfect for inside buildings—an impossible task for a 30-foot-tall driven pile rig.
Yet the length of a micropile isn’t dictated by headroom. Instead of a single, unwieldly structural element (such as a 30 ft driven steel caisson), the contractor can cut the structural elements of a micropile to length, then thread the sections together while drilling to reach any depth.
Adaptability, when soil conditions are difficult
From hollow-stem augers to hardened hammer-bits, micropile contractors can switch drilling techniques when needed. If the soil unexpectedly changes (say from sand to cobbles), the contractor can shift how they’re drilling and finish the pile for the client.
Whether it’s an underground boulder, high water tables, buried debris, gapping voids, or sloughing sands… adapting to the soil is what micropile contractors do best.
Sensitivity, when the worksite is touchy
Unlike driven piles that shake the ground and force excess soil to the side, micropiles are less damaging to the surroundings. Instead of displacing the soil, micropiles flush it to the surface up the hollow core of the drill stem. Because this method avoids vibrations, it’s ideal for soils that are prone to liquefaction. Or when a contractor is working next to a 1,000-year old Italian monument.
Drilling inside buildings typically means dealing with equipment fumes and loud noise, except when you use micropiles. Instead of a single, large piece of equipment (like a traditional piling rig), the contractor can dismantle micropile equipment into separate units, connecting them via long hoses. This means the contractor can put the noisy, diesel burning parts outside, and drill quietly, fume free, and with minimal equipment.
Capacity, when the pile is vital
When a pile fails, it’s costly for everyone involved. With micropiles, contractors know they can achieve loads from 500 to 5,000 kN, even in difficult soils. Micropiles are a safe bet because the contractor has ways to increase the load capacity even after testing the pile.
Most of a micropile’s capacity comes from skin friction. Along the entire length of the pile, a liquid grout grips the soil by seeping into the underground cracks and pores. This creates a long, strong, bond. And if the design load isn’t reached, the contractor can pump pressurized grout down the hole—repeatedly—to force an even stronger bond to the soil.
Pushing the Limits
Dr. Lizzi engineered a new technology to repair the deteriorating foundations of historic buildings. And ever since, specialty contractors have been testing the boundaries of what they can do with micropiles. From rescuing the Leaning Tower of Pisa in Italy to preventing settlement on the Mandalay Bay Resort & Casino in Las Vegas—micropiles are a niche solution with a promising future.
When there’s a project in need of an “impossible” support, it’s wise to talk to a foundation contractor with micropile experience.
Modern uses for micropiles include new builds—like bridges, buildings, or towers—as well as stabilizing slopes, reinforcing embankments, or retrofitting for seismic loads.
Tim Hirtle is an industrial-trades writer. His background is in heavy construction, engineering, and project management. He enjoys hearing from industry experts to discover what’s unfolding in their slice of the world.