Monday
Mar192018

Leading Thoughts: 3/19/18 Ground Improvement Transcends "Aggregate Piers"

Charles Allgood, P.E. explains why “aggregate piers” is inadequate terminology to describe modern ground improvement.

Lately I’ve noticed the construction community using the catch-all phrase “aggregate piers” to describe ground improvement.  Sometimes I even hear “agg piers!” This phrase might work for old-fashioned stone columns but our industry has advanced far beyond that with many new methods and materials.

The earliest use of “aggregate pier” I can find is a December 1994 article in Civil Engineering magazine.  This article, titled “Geopiers – short aggregate piers – provide an economical alternative to over-excavation/replacement…” was written by Dr. Nathaniel Fox, PE, the inventor of Geopier®.   So perhaps that set the stage.

Now we have Rammed Aggregate Pier® systems using both drilled and displacement methods.  Rigid Inclusion systems can be constructed with cement or grout admixtures (GeoConcrete Columns or Grouted Impact Piers) and even high-density plastic confining sleeves (Armorpact® piers); these are transforming what was previously referred to as the “aggregate pier” landscape. 

Geopier Armorpact under construction

Examples of Rammed Aggregate Pier are the Geopier GP3® system and the Geopier Impact® system.  These use crushed stone so they are closer to the aggregate pier description.  The GeoConcrete® and Grouted Impact® system are two rigid inclusion methods that have little in common with “aggregate piers” other than there is some aggregate in them! 

The common denominators are: there is a suite of ground improvement techniques to choose from, some are better than others in certain soil types, and all of them allow the structural engineer to design a building for normal spread footings and floor slabs-on-grade.

I suggest that more descriptive phrases be used by the construction community.  For instance, if you have an organic soil site you probably want a Rigid Inclusion method for foundation support, not an aggregate pier. 

If you have a contaminated site then you may lean towards a displacement (non-drilled) ground improvement solution.  If you have a variable fill site you should seek a drilled aggregate pier solution to give confidence that the fill is penetrated.  Tailor your wording to the best-fit technologies. 

I understand the impulse to be generic, but if sometimes you need to say Geopier go ahead and say it!  After all we brought ground improvement to the modern day construction site.

Ground improvement is so much more than “aggregate piers.”  Specify what you really want.  Enjoy the results.

Sunday
Feb182018

Leading Thoughts: 2/18/18 Client Benefits for Geopier® Ground Improvement

We asked Jeff Christensen, P.E., Senior Engineer at Ground Improvement Engineering, about the benefits of choosing Geopier® ground improvement.

 Geopier GP3® Construction

Does your project site have poor soils? Is your project in a tight, urban location? Are you looking for ways to save time and money? If you answered “yes” to any of these questions, let the experienced Geopier team evaluate your situation.  We will tailor a solution to address your needs.

Here are the three good reasons for the Owner or Design Team to choose Geopier ground improvement:

Cost Savings

Geopier ground improvement can save you money, especially compared to expensive deep foundations (piles, caissons, etc.) or over-excavation and replacement.

In the case of deep foundations we can help you switch back to normal footings and floor slabs-on-grade.

The cost of removing poor soils, trucking them offsite and importing select fill can be daunting. How about trying to dry the soils onsite for reuse?  A couple of rainy weeks will stop you in your tracks.

Dewatering or temporary shoring to protect existing buildings or utilities can add up, too. Why not improve the unsuitable soils in place to make things easier on your wallet? 

Smaller Footings

Geopier techniques create very stiff improved conditions for high soil bearing pressures. Smaller footings have less concrete, less reinforcing steel and require less labor, again putting money back in your project for other items.

Faster Schedules

We expect that you want to finish the project quickly and before the completion date. We can help with that by getting the work done quickly; often you can start foundations while we are still on the site.

So, what are you waiting for?  We can evaluate your project quickly and give you a budget that is realistic.  You have engaged a team that includes engineers and licensed contractors that have completed more than 8,000 Geopier ground improvement projects.  Now that is a lot of improved soil experience!

 

Contact our geotechnical engineers. Improve your site and put the savings to better use. 

Thursday
Jan112018

Leading Thoughts: 1/11/18 Geopier GeoConcrete® Column System replaces traditional Piles

We discussed the Geopier GeoConcrete® Column system with Aaron Gaul, P.E. He designs ground improvement projects in Colorado, Missouri and Oklahoma.

 

 The Geopier GeoConcrete Column system is a “Rigid Inclusion” alternative to conventional deep piling due to its simplicity and cost. This system allows structural engineers to design conventional spread footings over extremely soft and compressible soils. The GeoConcrete columns (GCC) provide high stiffness and support capacity.  They require a compacted granular pad to transfer the loads from the foundations to the GCC elements.

Our installers can build GCC elements very rapidly; this helps with client schedules. Plus, there is no structural tie-in between the footing and the ground improvement element. This eliminates thick, heavily reinforced pile caps.

Quality control is extremely important as would be for any conventional piling approach for soft and weak profiles. During Geopier GCC installation, a full-time Quality Control (QC) representative is present on site to verify and report all QC installation procedures and prepare Daily Geopier Progress Reports.

The Geopier GeoConcrete system is most suitable for soil profiles with compressible soil up to 50 feet below grade with a stiff layer below the compressible material. Depending on the geology, this system could be used anywhere in the United States.

 

The Residences - Oklahoma City, Oklahoma

Project Description:

The Residences is a 334 unit urban mixed-use development with retail, dining, and office space in the film row district of downtown Oklahoma City.  The project consists of six separate structures spanning three city blocks.  Two five-story wood framed apartment buildings make up the largest percentage of housing, along with a five-story concrete and wood frame clubhouse building with a rooftop pool and fitness center.

Parking is handled by multistory cast in place "Podium" parking as well as two precast parking garages over six stories tall.

This project will totally transform the west side of downtown Oklahoma City for years to come, creating an entire new community around the Historic Fred Jones Manufacturing Plant (currently the 21c Hotel).

Subsurface Conditions:

The site had a deep soft soil profile which consisted of  lean clay and sandy lean clay overlying sandy silt, silty sand, and sandy lean clay layers. Bedrock was about 45 feet below grade.

Solution:

Aaron Gaul, P.E. with Ground Improvement Engineering (GIE) designed the Geopier GeoConcrete Column system as an alternative to conventional deep piling parking garage.  Geopier Rammed Aggregate Pier® systems were used to support the lighter structures.

Monday
Nov202017

Project Spotlight: 11/20/17 Geopier Armorpact® is an Effective Method in Organic Soils

We talked to Stephen Weyda, P.E., a senior engineer with Ground Improvement Engineering who works out of Wisconsin and Northwest Illinois. He has been using the Geopier Armorpact® System since 2009.

Geopier Armorpact Installation

In Wisconsin, we have a lot of soft, alluvial organic soils. These organic soils are largely present in undrained areas that are adjacent to waterways and have different grades of organics like a topsoil or peat. When building along a body of water such as a lake, river or wetland, you’re more likely to find these types of soils. These organic soils require a rigid inclusion system, which better supports heavily loaded structures than standard aggregate pier systems. When you’re building an aggregate pier, organic materials degrade and tend to soften around the aggregate. The purpose of the Armorpact shell is to prevent softening of the pier as the result of the degradation of soils outside of the pier. A mandrel pipe is used to fill the shell from the bottom to the top. The Geopier Armorpact System locks a confinement sleeve into place. You now have a system that is robust enough to support the structure. 


Sometimes a competitor will propose a conventional aggregate pier system. We often educate the design team as to the benefits of using a more robust system, especially the geotechnical and structural engineers who understand the soil conditions and need for structural support. Without a robust system in place, the structure could face ongoing settlement throughout its life. This could lead to minor drywall cracking or greater concerns regarding the structural function of the building. We also explain how the upfront cost of the Geopier Armorpact System could be a cost savings down the road for the owner or developer.
 
Recent Geopier Armorpact System Projects

Marling Lumber Redevelopment, Madison, WI
We recently completed a project for the redevelopment of the Marling Lumber on East Washington in Madison, Wisconsin. This large, mixed-use project included multi-family residential units, retail and office space and a parking garage. We used the Geopier Armorpact System for all structures on the site – almost an entire city block. During the bidding process, some of our competitors didn’t address of organic soils. As a bonus over other rigid inclusions, is the flexibility of the Geopier Armorpact System. Let’s say you have an isolated layer at 10-15 feet with footings that drop down to that range. The Geopier Armorpact System allows you to cut the shells to fit the proper elevation. On the other hand, grouting is much more difficult to stop at the correct elevation. This project had footings at multiple levels and we were able to provide a solution to fit the needs of the project.  
Confluence Arts Center (CAC), Eau Claire, WI
We also completed work on the Confluence Arts Center in Eau Claire, Wisconsin. The 130,000 square foot arts center is on the confluence of two rivers in Eau Claire’s downtown. Due to its proximity to the rivers, this structure required a robust system to accommodate the soft, organic soils. This project started in fall 2016 and is slated to open in fall 2018. 
 
If your site has organic soils, you need to focus on what’s important to you as the owner or developer. Are you adverse to risk? What are your expectations for the long-term performance of the structure? The Geopier Armorpact System is a robust, long-term solution that reinforces the soils for more heavily loaded structures and it may just be the system for you.

 

 

Monday
Nov062017

Leading Thoughts: 11/6/17 Six Project Types that Benefit from Ground Improvement

As an engineering firm focused on Geopier® ground improvement, we at Ground Improvement Engineering work on many types of projects, each with its own unique challenges. Whether new construction or a building addition, properly designed ground improvement solutions will help the project construction go smoothly.

Our team is heavily based in research and development, so we are constantly looking at how we can improve. Here are six project types that benefit from ground improvement.

Grain Bins Agricultural yields are booming and with that comes the need for additional storage. Your geotechnical engineering consultant will explore the soils and anticipate how they will react to the loadings. They should also understand poor soil strategies such as over-excavation and replacement as well as ground improvement techniques like Geopier and deep pile foundations. After all, you do not want to be in a position where your site cannot support the grain bin and its contents.

Multi-Story Housing and Retail Construction projects that are multiple stories will often need some sort of ground improvement solution, especially if the project is on a tough site with multiple soil types. Solutions such as the Geopier Densipact® system or Geopier Rammed Aggregate Pier® Systems are used to densify or reinforce the soil so it can support the loads of the multi-story building.

School and University Buildings We work on a lot of school additions and new buildings, including the Integrated Science and Engineering Laboratory Facility (ISELF) at St. Cloud State University. Identifying the ground improvement needs of the site of an education facility will help you save time and money during the construction of the project, and help extend the life of the building. This is important to note as schools and universities can have tight budgets and construction deadlines.

Sports Fields and Stadiums You would probably never guess the level of difficulty presented by the Augustana College Football Stadium site. Click here for a full project overview. We understand how important the placement of a sports field or stadium is to the team and its fans. Ground improvement solutions can help these projects move forward, even when less than ideal soil conditions are present.

Walls and Embankments Depending on the size of your project, soil conditions can vary throughout a site. Before erecting a wall or embankment, you’ll need to know if there is any need for an increase in bearing capacity. From there, a ground improvement solution like Geopier GP3 System can be used (as it was for this project) to limit the need for more expensive solutions. Geopier elements can also perform a dual role as ground improvement and drainage if needed.

Wind Turbines In recent years, a greater focus has been placed on renewable energy. We are currently working on multiple wind farms across the Midwest. Our job often starts by working with the geotechnical engineers on the feasibility of wind energy projects before they go out to bid. Due to their location, these sites often have soft, deep soils that are too expensive to dig out. Most commonly, we will use the Geopier GP3 System and Geopier X1® System for ground improvement because they make the most economic sense. Learn more about our experience working on wind energy projects here.

If the soil conditions of your site are less than ideal, you need to consider ground improvement to help ensure the safety and efficiency of your crew. Time is valuable in the construction world. Working with a firm like Ground Improvement Engineering can save you time, money and headaches throughout the project.