Deep Foundations – Comparing the Displacement of Pipe Shaft Helical Piles

Posted by Jason Herron, P.E., C.W.I. on May 14, 2021 1:00:00 PM

Helical piles are a displacement piling system that moves the soil away from the central axis of the shaft. This has many advantages that include no spoils to remove, but also comes with disadvantages as the shaft diameter increases. The helical piling industry categorizes pipe helical piles into low, medium, and high displacement. Each category has advantages and disadvantages that a specifying engineer must consider when selecting a pile that is applicable and economical for the project.

Low Displacement

The largest volume pipe shaft helical pile used in the North American market are low displacement pipe piles. Low displacement piles are defined as piles with central shaft diameters up to 4.5 inches.

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Topics: Foundations, Civil, Engineering, High Capacity Piles

How to Determine Helical Pile Capacity with Limited Soil Data

Posted by Josh Lindberg on Apr 21, 2021 7:40:00 AM

On many construction projects, soil borings are not completed due to the property owner wanting to reduce costs or, quite simply, being unaware of the need to obtain soil strength data for foundation design. During the installation of CHANCE® Helical piles, monitoring torque can provide real time data defining underlying soil strength and its load capacity. As a helical pile is installed (screwed) into increasingly denser/harder soil, the resistance to installation (called installation energy or torque) will increase. The higher the torque, the higher the axial capacity. In most projects, the installation torque increases with depth, and the capacity of CHANCE helical piles can be determined at the time of installation. Regardless of whether the pile is being installed in clay or sand soil, the torque to correlation factor (Kt) for each shaft size, is multiplied by the effective installation torque (T), resulting in the ultimate capacity for each pile. The standard equation for ultimate capacity is Kt * T. The torque correlation factors for CHANCE helical piles can be found in the CHANCE Technical Design Manual-4th Edition. The effective torque is the average torque taken over the last 3 feet of installed depth, measured in 1 foot increments.

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Topics: Foundations, Civil, Engineering, Contractors, Torque

Helical Pile Shaft Optimization

Posted by Gary L. Seider, PE on Apr 8, 2021 9:45:00 AM

The shaft type/size of a helical pile is critical to both the axial and lateral capacity – especially for compression in soft/loose overburden soils where lateral stability of the shaft must be considered.  The following is a brief summary of the 4 different shaft types commonly used for helical piles and their relative advantages and disadvantages based on site conditions and application.  It is very important to understand that helical pile installation must be considered in the design process.

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Topics: Helical Pile Benefits, Civil, Engineering

Pushing Boundaries with High Capacity Helical Piles

Posted by Stephen Scott, EIT on Mar 29, 2021 8:30:00 AM

As the concepts and design of modern structures continue to evolve, so too must the deep foundation systems on which they are founded upon. With the help of modern technology and material science, structural boundaries continue to be pushed and economic considerations are causing a trend toward the increased use of high-capacity piles. In response to the demand, helical piles have expanded beyond light and medium loaded structures and have been engineered to support heavily loaded structures subjected to both compression and tension.

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Topics: Construction, Engineering, Helical Pile Applications, High Capacity Piles

Helical Piles vs Concrete Drilled Shafts (Caissons)

Posted by Shawn Downey on Mar 2, 2021 4:39:03 PM

There are several solutions engineers and contractors can choose from when a deep foundation is required. With a deep foundation the structure’s load is transmitted to soils that are deeper in the ground. A deep foundation is used when a shallow foundation is not possible, not practical, or will not carry the load. Examples are weak, unstable, or expansive surface soils. Two popular options for deep foundations are helical piles and drilled shafts, also known as drilled piers or caissons.

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Topics: Construction, Foundations, Helical Pile Benefits, Civil, Engineering

Getting an Accurate Helical Pile Bid

Posted by EBS Geostructural on Oct 20, 2020 9:29:00 AM

Deep foundation pricing is multifaceted and a one price fits all approach can lead to unexpected costs. To break down the pricing, the following list can help provide a better understanding of the top 4 factors that can affect pile prices and why they are important pieces of information when looking for estimates:

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Topics: Construction, Helical Pile Benefits, Civil, Engineering

3 Methods to Determine Helical Pile Capacity (and why you should use 2)

Posted by Gary L. Seider, PE on Oct 1, 2020 7:30:00 AM

The load capacity of helical piles can be determined 3 ways. The method(s) used are dictated by the information available. The capacity of a helical pile must equal or exceed the factored load that the pile is required to support.

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Topics: Civil, Engineering, Torque

Engineered helical piles for lateral load capacity on ballistic barriers

Posted by Josh Lindberg on Jul 24, 2020 9:49:00 AM

Helical piles are an established solution for foundation underpinning, but their applications are as far-reaching as the creativity of an engineer. Helical piles are typically associated with gravity load - force pushing down on the pile. In the project below, helical piles are utilized to support lateral loads, including wind and seismic loads.

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Topics: Construction, Engineering, Helical Pile Applications

Vertical and Battered Helical Pile Groups to Mobilize Lateral Load Capacity

Posted by Jason Herron, P.E., C.W.I. on Jul 9, 2020 8:15:00 AM

Helical piles have become a common piling system in the North American construction market.  They are used for many applications with low to moderate tension and compression loads.  Slender helical piles, less than 4.5 inches in diameter, have historically been used for light shear loads of 1 to 5 kips in vertical applications. This method derives the lateral capacity as a function of the pile’s allowable structural bending moment and the allowable passive earth pressure of the soil. It is common to analyze the capacity of the piles by theoretical slender pile equations, P-Y curves, or software programs that model P-Y response. An adequate safety factor or a service limit on the allowable deflection is applied to the allowable loads to determine an applicable pipe size. In recent years larger piles, with diameter greater than 5.5 inches, have been used for larger lateral loads.  Large diameter piles have been designed for loads in excess of 20 kips. 

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Topics: Foundations, Helical Pile Benefits, Engineering

Origin and Development of the Torque Correlation (Kt) Factor

Posted by Gary L. Seider, PE on Jun 11, 2020 11:23:14 AM

Today, it is generally accepted that installation torque can be used to verify the axial capacity of helical piles.  The International Building Code (IBC) 2012, 2015 & 2018 Section 1810. states there are three ways to determine axial capacity.  Method 2 states the ultimate capacity can be determined from well documented correlations with installation torque.  The installation torque-to-capacity relationship is an empirical method originally developed by the A. B. Chance Company in the late 1950’s and early 1960’s. For over 60 years, Hubbell Power Systems, Inc. has promoted the concept that the torsion energy required to install a helical anchor/pile can be related to its ultimate capacity.  Precise definition of the relationship for all possible variables is the subject of on-going research.  However, simple empirical relationships, originally derived for tension applications but also valid for compression capacity; continue to be used as part of project specifications to verify capacity.  The principle is that as a helical anchor/pile is installed (screwed) into increasingly denser/harder soil, the resistance to installation (called installation energy or torque) will increase.  Likewise, the higher the installation torque, the higher the axial capacity of the installed pile/anchor.  The CHANCE® torque correlation equation is:

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Topics: Foundations, Engineering, Torque

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