The unique design of the screw pile product enables it to be used in areas where limited site access, noise, vibration and/or overhead clearance would prohibit the use of piling installed by conventional impact or
vibratory driving methods. The screw pile is constructed of reinforced concrete; having a solid reinforced concrete core of 5" and an outside diameter of approximately 8 ¾”. The helical threads cast around
the piles core allow the pile to be "driven" into the soil by application of torque to the pile; i.e. literally screwing the pile into the ground.
The screw pile behaves as a friction-type pile; it develops its load capacity in the same manner as timber, concrete or steel friction-type piles. Piles of this type develop load capacity through the development of sharing resistance between the soil and the pile surface. Therefore, the ultimate load-bearing capacity for any friction type pile
in a given soil is a function of the piles surface area. When compared on a unit length bases to a typical Class 9 timber pile, commonly used in residential construction (Type I and Type J occupancies), the
screw pile conservatively provides a 60 % increase in surface area over the conventional pile. Similarly, the screw pile provides a 35% increase in surface area over a Class 5 timber pile. Preliminary
load test of the screw pile indicate that a 20´ pile will carry a safe design load of 2 ½ to 4 ½ tons, depending upon soil conditions.
The screw pile offers the following advantages over conventional piling:
Ease of Installation -
The screw pile can be installed with a minimum of the equipment and manpower. Due to its unique screw thread the sign, the screw pile can be installed and adjusted to exact elevations.
Limited Site Access -
The machinery necessary for screw pile installation is small and unobtrusive; permitting access and installation in very close quarters not accessible by conventional pile driving equipment.
Elimination of Noise & Vibration -
Because the screw pile is installed by non-percussive means, the noise, concussion and vibratory nuisance associated with pile driving operations are virtually eliminated.
Constructed of reinforced concrete, the screw pile is not affected by termites or rot.
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Screw piles are fabricated by Reddi-Walk and Leveling Services at their plant facility. Piles are cast from three-piece split forms and can be cast in 5´ cylindrical, 10´ cylindrical or 10´ tapered
lengths. Forms are constructed of a steel outer casing which supports an interior hard rubber mold. These forms are suspended vertically from racks; each rack carries six or eight molds.
Concrete mix for screw piles has a design flexural strength of 6,000 psi and is mixed on-site using a power mixer. Once the concrete is properly mixed it is introduced into the forms via a bucket lift.
The placed concrete is consolidated by means of an internal vibrator for approximately 60 seconds. After vibration, the reinforcement alignment is checked and adjusted as required. Every 25 pilings, a
test cylinder is made and broken at 14 days to insure quality of concrete and uniformity of mix design between batches. The heads of each pile are scribed marked with its date of manufacture once the concrete has
sufficiently set. The piles are allowed to set for 24 hours before additional handling.