Geopier MythBusters: Ground improvement edition

Geopier MythBusters: Ground improvement edition



Welcome back to Geopier’s version of MythBusters, where we dispel some of the Geopier® related myths circulating in the design-build world.  This article is a continuation of our first season of Geopier MythBusters, where we discussed constructing piers below the groundwater table and supporting heavy loads.  This article will focus on two more myths:

Myth 3: Geopier systems cannot be used in soft clays and organic soils.

Myth 4: Geopier is not cost effective on small projects.

Our hope is that these MythBusters help you better understand our capabilities so that you can design using Geopier with confidence.

Myth 3: Geopier systems cannot be used in soft clays and organic soils.

Sites with deep soft clay/organic soils can be problematic for engineers, general contractors and developers, alike.  The risks of excessive total and differential settlements are very real and could result in severe structural distress if not accounted for properly.  Conventional solutions in the industry consist of:

  • Deep foundations: Deep foundations deliver excellent settlement control by simply transferring building loads through the soft clay/organic soils and into a competent bearing layer. However, deep foundations are typically expensive and time consuming to install. They also require structural slabs and pile caps, which can add significant cost and time to a project.
  • Surcharge/wick drains: Another option for soft clay/organic sites is to place a soil surcharge over the footprint of the building that meets/exceeds the total weight of the proposed structure. This process can require months/years to complete depending on how thick the organic/clay layers are. The process can be expedited with wick drains, but that adds cost to the project and can still require a significant amount of time. In today’s construction market, time is of the essence.

Geopier has a third solution for these soft clay/organic sites that is becoming more and more common in the industry. We are referring to rigid inclusions. 

  1. Rigid inclusions are sort of a hybrid between our rammed aggregate pier solutions and deep foundations.
  2. Rigid inclusions are very stiff, cementitious elements that provide the same excellent settlement control as deep foundations by transferring the building loads through the weak soils and into a competent bearing layer.
  3. The cementitious nature of the rigid inclusions prevents bulging of the elements into the weaker soils.
  4. Rigid inclusions allow the foundations and floor slabs to be designed as conventional spread footings and slabs-on-grade, respectively, which can significantly reduce project costs versus a structural slab and pile cap system. 
  5. Rigid inclusions are very quick and easy to install and don’t require a structural connection to the overlying superstructure.

If you would like to learn more about Geopier rigid inclusion design and solutions, please watch our recent webinar, Geopier Ground Improvement Solutions for Organic & Soft Soils. A PDH certificate will be provided.

Myth 4: Geopier is not cost effective on small projects

I have heard on multiple occasions that Geopier was not asked to look at a project because “Geopier does not do small jobs.” The truth is that we can almost always add value to a project, whether it is small retail store, MOB, or residential structure. Consider these “small” nuggets of truth:

  • In the past three years, nearly 30 percent of Geopier projects were small (200 piers or less) with 15 percent having less than 100 piers.
  • Even on small jobs, we can typically add value versus removal and replacement whenever more than 5 feet of unsuitable materials need to be removed. That depth can be even less if the soils are environmentally impacted. 
  • If your project has heavy loads, we can almost always increase the design bearing pressure. This allows for a reduction in footing sizes that offsets the cost of adding Geopiers. Sounds like a win-win! 
  • Especially on small jobs, we can add significant value versus a deep foundation solution where the cost of the deep foundation relative to structure can be very high. As an added benefit, the foundations and slabs supported by Geopiers can be designed and constructed as conventional spread footings and slabs-on-grade. 
  • We even have an annual “Guppy Award” for the project with the least number of Geopiers!

So next time you have a small project, call Geopier. We look forward to adding value in any way we can.

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