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Communications Tower Foundation for Rural Region (Very Dense Soils)
Client was initially told helical piles "couldn't be done", VersaPile steps in to provide a helical solution where others couldn't
Client
Xplornet (Xplore)
Project
Communications Tower
Location
Harold Lake, MB
Pile Details
273mm (10-3/4") Ø shaft, 13mm (1/2") thick wall, 607mm (24") double helix
Refusal
End Bearing
Soil Conditions
Very Dense Till at 4.9m (16ft)
Problem
VersaPile was engaged prior to construction by Xplornet to support a 46m (150ft) communications tower to bring rural high speed internet to the surrounding community of Harold Lake, Manitoba.
The geotechnical investigation encountered SPT refusal at 4.9m (16ft) depth with very dense soils with N values in excess of 50 from 2.5m. The client's strong preference for the foundation was helical piles, but the very dense soils meant reaching minimum embedment of 4.9m would prove challenging.
VersaPile was told by a seasoned helical pile company with extensive experience in the utility sector that the soils were too dense to achieve the desired results with helical piles. However, the client was determined and our team was up to the challenge.
The alternative foundation of a large concrete pad is much less desired by companies such as Xplornet who often lease land for communications towers.
Helical piles are, in general, less expensive than concrete pads - especially in rural locations. They're also far easier to uninstall and fully remediate when the land lease expires and the tower must be decommissioned.
Solution
VersaPile engaged Cory Goulet P.Eng. of Pilisk Geostructural as well as Silvestre S. Urbano of SSU Geotechnical Engineering, to analyze the soil and helical pile design options.
Together, they engineered a helical solution that would survive the installation to minimum embedment as well as satisfy the design criteria.
The solution was to engineer larger piles which could withstand high torques as well as gain resistance in friction.
In addition to the more robust piles, VersaPile designed a high torque 152mm (6in) pre-drill bit equal to 56% of the diameter of the pile shaft. This was utilized to pre-drill through dense soils layers, which reduced installation resistance without compromising performance.
The 115ft-kip helical drive that VersaPile might utilize for a tower project like this was instead swapped for a larger Digga UD300 drive that could produce up to 226ft-kip torque. This increased torque from the larger helical drive gave our installers the muscle needed to install the piles through dense soils.
Conclusion
VersaPile, along with a team of project engineers, installed 6 helical piles into the dense soil (2 per leg). Despite the dense soils, the combination of pre-drilling and increase torque from the larger helical drive worked perfectly to smoothly and efficiently install the piles.
These piles were finished by having I-beam pile caps welded to the top by DC Custom Welding. The I-beams transitioned the piles in the ground to the legs of the communication tower, providing a sturdy and durable connection.
A project that was initially deemed "impossible" by other helical companies was made possible through the creative thinking and hard work of VersaPile and our valued engineering partners Cory Goulet P.Eng. and Silvestre S. Urbano.
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2046 Van Gorp Road
Ile Des Chenes, MBCanada R0A 0T0
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Monday - Friday8:00 - 17:00
Contact
(234) 567-8900moc.elipasrev%40olleh