We train installers, offer assistance to other pile companies
Helical piles are one of the most reliable foundation solutions, and will perform as designed invariably, as long as the installation procedures strictly adhere to the protocol set out in AC358 and 2009 IBC guidelines for the design, installation, and verification of the ultimate helical pile capacity.
This is because helical pile installation provides real-time, redundant on-site feedback of the soil capacity and pile load bearing capacity, through:
- Torque monitoring of the installation equipment (through residual hydraulic pressure, torque measuring devices)
- Torque monitoring through bolt hole elongation and shear-pin monitoring
- Gradual torque resistance which follows SPT / CPT soil investigation
- Dynamic pile settlement test conducted on-site
The load bearing capacity of a helical pile is given by the relationship: Qu = T x k where the Qu is the ultimate bearing resistance of the helical pile (lb, kips, kN), the T is the torque of the pile installation at maximum depth (ft-lb, ft-kips, kNm) and k is a pile specific constant (1/ft, 1/m).
This relationship enables anyone to know, at any time during the pile installation, what is the ultimate bearing capacity of the pile he/she is installing at that very moment. With this, the installer knows when to stop the pile advancement (and most important, when to continue with the installation to deeper layers, if the pile did not achieve the required resistance).
Helical piles use a minimumFactor of Safety of 2.0.
T (Torque) information is provided by the manufacturer of the hydraulic torque head; they provide a graph which will show the Torque for any given hydraulic pressure in the system. The hydraulic pressure is directly related to the Torque output of the head. The higher the pressure in the system, the higher the Torque of the head will be. The hydraulic system effect on the torque head is simple:
- Pressure (measured in psi) in the system is directly related to the Torque of the head; the higher the psi, the higher the Torque.
- Flow (measured in GPM) is related to the rotational speed of the head; the higher the GPM, the faster the head will rotate. For pile installation, aim to have a rotational speed of 14 revolutions per minute.
K is a pile specific constant. The simplicity of the pile installation is that k does not depend of the diameter of the helix, on the pile manufacturer, etc. K is related to the diameter of the shaft only, and is universal (mostly) between various manufacturers and pile helix diameters. It is also not related to the soil type. K depends only (mostly) on the diameter of the pile shaft. A table with k values for different shaft diameters is all the pile installer needs. Manufactures will provide this table. The installer only needs to know the diameter of the shaft he is installing.
Let’s look at one example: an installer is using a 3.5” diameter pile, with a 12” helix (however, the size of the helix does not matter, as it does not influence the equation above). The installer needs to get an ultimate bearing resistance of 30,000 lb (and therefore an allowable pile resistance of 15,000 lb). Aside from the fact that the diameter of the shaft is 3.5”, no other information is required by the installer (the helix diameter, type of soil, pitch of the pile do not significantly affect these calculations).
For the installer: Qu = T x k
1) The installer needs to install the pile, and constantly monitor the hydraulic pressure in the system. This will give him the Torque.
2) The installer needs to read the k value for the 3.5” shaft diameter (provided by the manufacturer of the pile). K value for a 3.5” pile is = 7 (units of 1/ft)
- At 5’ depths, the installer is reading a Torque of 1,000 ft-lb, which means his pile will have an ultimate bearing capacity of 1,000( ft-lb) x 7 (1/ft) = 7,000 lb.
- At 10’ depths, the installer is reading a Torque of 2,000 ft-lb, which means his pile will have an ultimate bearing capacity of 2,000 (ft-lb) x 7 (1/ft) = 14,000 lb.
- At 15’ depths, the installer is reading a Torque of 3,000 ft-lb, which means his pile will have an ultimate bearing capacity of 3,000 (ft-lb) x 7 (1/ft) = 21,000 lb.
- At 18’ depths, the installer is reading a Torque of 4000 ft-lb, which means his pile will have an ultimate bearing capacity of 4,000 (ft-lb) x 7 (1/ft) = 28,000 lb.
- At 20’ depths, the installer is reading a Torque of 4,500 ft-lb, which means his pile will have an ultimate bearing capacity of 4,500 (ft-lb) x 7 (1/ft) = 31,500 lb.
The pile installer may decide to stop the installation of the helical pile. If the installation complied with the instructions, and coupled with additional information about the installation and additional tests and observations, the installer and the project team can be confident that the helical pile installed will safely support the 30,000 lb required by the designers.
One side note about the equipment necessary to install such pile: To obtain a torque of 4,500 ft-lb., roughly, a minimum of 17 HP able equipment is necessary. That could be a power pack, a 1.5 ton mini excavator, skidsteer, etc. The hydraulic pump of the equipment is required to produce 2500 psi at roughly (preferably) 8-10 GPM flow or more. Most available small excavators (from any rental place) would be capable of delivering such conditions.
The most important training, formation and education for any new prospective pile installer (and existing ones) is safety training, and forming the habit to comply with Work Safe BC in applying all rules and regulations in working with helical piles. In most aspects, these are the same with the safety procedures for excavating / digging. The safety risks are numerous, and simply cannot be listed and explained here. To fully comply with these rules and regulations, training, on site practice and classroom study is necessary for every single worker and supervisor. There is simply no substitute for solid and ample safety training, safe work procedures and safe habits.
No one should install helical piles without undertaking first rigorous training, education and job-site training specifically prepared for helical piles. Safety in the installation of helical piles does not end only with “Call Before You Dig”. Numerous other hazards and safety concerns need to be addressed and eliminated. For anyone who is not fully experienced in helical pile installation, they are simply not aware of the inherent dangers and safety risks involved. However, with proper training, education and on-the-job orientation and apprenticeship, most or all the risks can be eliminated. We recommend to anyone who is interested in installing helical piles to ensure that they comply with all the rules and regulations set forth by work Safe BC. However, as explained above, simply complying with these statue regulations is not enough; it is merely the beginning. Helical piles specific training and experience is necessary to provide the rest of the safety training.
BC Helical Piles is pleased to assist you with any of the following:
- Purchasing helical piles; we sell helical piles to the experienced contractors.
- Equipment rental or purchase.
- Provide contact of equipment manufacturers.
- Provide training, offer assistance to contractors who want to become helical pile installers.
Provide engineering support to contractors / helical pile installers.
This is because helical pile installation provides real-time, redundant on-site feedback of the soil capacity and pile load bearing capacity, through:
- Torque monitoring of the installation equipment (through residual hydraulic pressure, torque measuring devices)
- Torque monitoring through bolt hole elongation and shear-pin monitoring
- Gradual torque resistance which follows SPT / CPT soil investigation
- Dynamic pile settlement test conducted on-site
The load bearing capacity of a helical pile is given by the relationship: Qu = T x k where the Qu is the ultimate bearing resistance of the helical pile (lb, kips, kN), the T is the torque of the pile installation at maximum depth (ft-lb, ft-kips, kNm) and k is a pile specific constant (1/ft, 1/m).
This relationship enables anyone to know, at any time during the pile installation, what is the ultimate bearing capacity of the pile he/she is installing at that very moment. With this, the installer knows when to stop the pile advancement (and most important, when to continue with the installation to deeper layers, if the pile did not achieve the required resistance).
Helical piles use a minimumFactor of Safety of 2.0.
T (Torque) information is provided by the manufacturer of the hydraulic torque head; they provide a graph which will show the Torque for any given hydraulic pressure in the system. The hydraulic pressure is directly related to the Torque output of the head. The higher the pressure in the system, the higher the Torque of the head will be. The hydraulic system effect on the torque head is simple:
- Pressure (measured in psi) in the system is directly related to the Torque of the head; the higher the psi, the higher the Torque.
- Flow (measured in GPM) is related to the rotational speed of the head; the higher the GPM, the faster the head will rotate. For pile installation, aim to have a rotational speed of 14 revolutions per minute.
K is a pile specific constant. The simplicity of the pile installation is that k does not depend of the diameter of the helix, on the pile manufacturer, etc. K is related to the diameter of the shaft only, and is universal (mostly) between various manufacturers and pile helix diameters. It is also not related to the soil type. K depends only (mostly) on the diameter of the pile shaft. A table with k values for different shaft diameters is all the pile installer needs. Manufactures will provide this table. The installer only needs to know the diameter of the shaft he is installing.
Let’s look at one example: an installer is using a 3.5” diameter pile, with a 12” helix (however, the size of the helix does not matter, as it does not influence the equation above). The installer needs to get an ultimate bearing resistance of 30,000 lb (and therefore an allowable pile resistance of 15,000 lb). Aside from the fact that the diameter of the shaft is 3.5”, no other information is required by the installer (the helix diameter, type of soil, pitch of the pile do not significantly affect these calculations).
For the installer: Qu = T x k
1) The installer needs to install the pile, and constantly monitor the hydraulic pressure in the system. This will give him the Torque.
2) The installer needs to read the k value for the 3.5” shaft diameter (provided by the manufacturer of the pile). K value for a 3.5” pile is = 7 (units of 1/ft)
- At 5’ depths, the installer is reading a Torque of 1,000 ft-lb, which means his pile will have an ultimate bearing capacity of 1,000( ft-lb) x 7 (1/ft) = 7,000 lb.
- At 10’ depths, the installer is reading a Torque of 2,000 ft-lb, which means his pile will have an ultimate bearing capacity of 2,000 (ft-lb) x 7 (1/ft) = 14,000 lb.
- At 15’ depths, the installer is reading a Torque of 3,000 ft-lb, which means his pile will have an ultimate bearing capacity of 3,000 (ft-lb) x 7 (1/ft) = 21,000 lb.
- At 18’ depths, the installer is reading a Torque of 4000 ft-lb, which means his pile will have an ultimate bearing capacity of 4,000 (ft-lb) x 7 (1/ft) = 28,000 lb.
- At 20’ depths, the installer is reading a Torque of 4,500 ft-lb, which means his pile will have an ultimate bearing capacity of 4,500 (ft-lb) x 7 (1/ft) = 31,500 lb.
The pile installer may decide to stop the installation of the helical pile. If the installation complied with the instructions, and coupled with additional information about the installation and additional tests and observations, the installer and the project team can be confident that the helical pile installed will safely support the 30,000 lb required by the designers.
One side note about the equipment necessary to install such pile: To obtain a torque of 4,500 ft-lb., roughly, a minimum of 17 HP able equipment is necessary. That could be a power pack, a 1.5 ton mini excavator, skidsteer, etc. The hydraulic pump of the equipment is required to produce 2500 psi at roughly (preferably) 8-10 GPM flow or more. Most available small excavators (from any rental place) would be capable of delivering such conditions.
The most important training, formation and education for any new prospective pile installer (and existing ones) is safety training, and forming the habit to comply with Work Safe BC in applying all rules and regulations in working with helical piles. In most aspects, these are the same with the safety procedures for excavating / digging. The safety risks are numerous, and simply cannot be listed and explained here. To fully comply with these rules and regulations, training, on site practice and classroom study is necessary for every single worker and supervisor. There is simply no substitute for solid and ample safety training, safe work procedures and safe habits.
No one should install helical piles without undertaking first rigorous training, education and job-site training specifically prepared for helical piles. Safety in the installation of helical piles does not end only with “Call Before You Dig”. Numerous other hazards and safety concerns need to be addressed and eliminated. For anyone who is not fully experienced in helical pile installation, they are simply not aware of the inherent dangers and safety risks involved. However, with proper training, education and on-the-job orientation and apprenticeship, most or all the risks can be eliminated. We recommend to anyone who is interested in installing helical piles to ensure that they comply with all the rules and regulations set forth by work Safe BC. However, as explained above, simply complying with these statue regulations is not enough; it is merely the beginning. Helical piles specific training and experience is necessary to provide the rest of the safety training.
BC Helical Piles is pleased to assist you with any of the following:
- Purchasing helical piles; we sell helical piles to the experienced contractors.
- Equipment rental or purchase.
- Provide contact of equipment manufacturers.
- Provide training, offer assistance to contractors who want to become helical pile installers.
Provide engineering support to contractors / helical pile installers.