Leading Thoughts: 1/22/19 Ground Improvement Myths – New Geopier® Techniques
Charles Allgood, P.E., consults with Matt Caskey, P.E. from Geopier Foundation Company about how Geopier technology has advanced to improve nearly any tough soil condition, busting many myths that still persist about Geopier ground improvement.
The family of ground improvement technologies known as Geopier® began in the late 1980s as a replacement for over-excavation in the Atlanta, Georgia. The technologies have advanced tremendously over the years — with more than 10 Geopier Rammed Aggregate Pier® and Geopier rigid inclusion options available to handle nearly every ground improvement and/or deep foundation need. Despite this there are misconceptions and myths about its true capabilities.
Here are three common myths we still hear about Geopier — along with our myth-busting facts. These facts come from nearly 10,000 (and counting) projects and experience that our Ground Improvement Engineering team has demonstrated with Geopier solutions. With each project, we refine our newer techniques and add to our knowledge, so this post also provides simple tips for project managers to take another look at Geopier for tough soils and deep foundations.
Myth #1: You can’t install piers in areas with shallow groundwater.
Project managers and even geotechnical engineers continuously believe this myth, but as written about in a previous blog post, Geopier systems are commonly used on sites with shallow groundwater. Current techniques include the use of displacement and partial-displacement methods, switching to open-graded clean crushed rock, and even utilizing old-school temporary casing, that can handle upward pressure, seepage and soil instability.
In fact, today’s new displacement systems keep our team very busy at sites with shallow groundwater that were previously uneconomical to develop. New Geopier techniques make ground improvement at these sites relatively easy.
Myth #2: You can’t go deeper than 20 feet with Geopier.
In truth, the old Geopier “drill and fill” depth restrictions of 20 to 25 feet are long gone. We have developed new methods that can install Geopier systems 60 to 65 feet deep. This is a true game changer when it comes to very deep soft soil deposits beneath buildings as well as tanks and embankments. Project managers can now consider Geopier at greater depths with confidence.
Myth #3: You can’t use Geopier for slope stabilization.
Actually, due to the unmatched compaction energy used to construct Geopier Rammed Aggregate Piers, we can design for substantial increases in frictional resistance and dramatically improved composite shear parameters in slope stabilization. We can also use reclaimed or salvaged aggregates to build Geopier systems. We frequently use Geopier for slope stabilization on highway projects, approach embankments and bridges. For private projects, we have used Geopier for buildings next to slopes and/or natural features such as lakes.
Tips for Project Managers
After reconsidering perceptions about Geopier, project managers can derive some true game-changing benefits from the advanced ground improvement techniques now available. Here are a few of them:
Less vibration – Particularly in urban environments with noise ordinances, Geopier technology results in less vibration than traditional pile driving or alternative stone column approaches.
Simultaneous scheduling – Contractors can start foundation work while ground improvement is happening elsewhere on the project. Our teams can ramp up quickly when the project needs us there, and the installation is very fast, helping to keep foundation work on schedule.
Year-round methods – More and more, we are doing ground improvement in the winter months when excavation/refill is not practical. As long as the ground is kept thawed before and after pier installation, we can work hand-in-hand with the contractor to help them improve tough soils and continue winter construction.
Now that we’ve busted some myths about modern Geopier technology, isn’t it time to rethink your ground improvement options?
BONUS MYTH:
Myth #4: I can’t use a Geopier system unless it is recommended in my geotechnical report.
Geopier systems can be evaluated at any time during a project’s development, Experienced geotechnical designers with Ground Improvement Engineering or Geopier Foundation Company can assist the project team by offering design-build solutions that meet or exceed project performance specifications for structural support and settlement control. Many times a Geopier solution has resolved deep foundation cost and schedule burdens that would otherwise jeopardize project feasibility.