Steel Screw Piles

Steel Screw Piles

Steel helical piles typically consist of a round steel shaft and one or more helical plates. Spacing between any two helixes is usually 3 times the diameter. Helix size and quantity will depend upon the required capacity of the steel screw pile and the soil properties and condition

A steel screw pile is a circular hollow steel pipe section (shaft) with one or more tapered steel plates (helixes) welded to the shaft. Each steel plate is shaped into a helix with a carefully controlled pitch.  This precision allows the steel screw pile to be inserted into the ground with minimal soil disruption.  The central shaft is used to transmit torque during installation and to transfer axial loads to the helical plates upon foundation loading. The central shaft also provides a major component of the resistance to lateral loading. The steel screw pile is directed toward the soil and mechanically rotated with constant downward pressure, advancing the steel screw pile into the soil. Once installed, the anchor has bearing capacity in both tension and compression in the subsurface by transferring the structures load to the bearing stratum. The steel screw pile installation angle can range from vertical to nearly horizontal

Steel screw pile foundations are also referred to as helical anchors, screw anchors, torque piles or helical piles or piers. In this manual screw anchors will assume to be in tension and steel screw piles in compression.

Pile Drive have various foundation solutions to cater for horizontal loads and  bending moments, suitable for supporting rail signals including Straight Signal Posts, OLE Columns and other similar structures.

In conjunction with steel screw piles, bespoke designs can also be supplied for sites where space is limited or to bridge buried services.  Steel screw pile lengths and diameters vary according to ground conditions

Pile Drive steel screw piles and screw anchors typically consist of a round steel shaft and one or more helical plates. Spacing between any two helixes is usually three times the diameter of the smaller, lower helix and set in increments of the helix pitch. Helix size and quantity will depend upon the required capacity of the pile and the soil properties and conditions.

Design Criteria 

Bearing capacity depends on the following variables: 

  • Type and properties of the soil; 
  •  Surface and/or groundwater conditions; 
  •  Geometry of the pile (pipe size, helix size, number of helixes, material thickness); 
  • Pile material (new steel only); 
  • Size of pile (cross-section, length); 
  • Embedment depth of pile; 
  • Position of pile (vertical, horizontal or battered); 
  • Spacing between piles (interaction of piles, group effect); 
  • Installation torque; and 
  • Type of loading (static, cyclic, step-loading, dynamic loading such as harmonic loading, impact, transient and others).

Installation 

For steel screw piles subjected to uplift and/or frost jacking the embedment depth of the uppermost helix shall be at least five (5) helix diameters or deeper than the maximum frost penetration depth that is in the area. The leading edge on the helical plates are rounded back and sharpened to facilitate installation and to minimize disturbance of the soil during installation.

The lead ends of the piles are cut to a 45º angle to aid in targeting of the pile during installation. 

Helixes are cut from plate steel and formed using matching metal dies. The dies are set to provide the helix with the required pitch. The helical shape is a “true flight”. The helical plate shall be normal to the central shaft (within three degrees) over its entire length. The helix is shaped so that it threads into the soil much like a wood screw going into a piece of wood.

Steel screw piles are installed into the ground via drive head motors using rotary hydraulics attached to a variety of equipment. Boom mounted power utility trucks, skid steers, mini and large excavators and many other types of equipment, even handheld units are used. 

Torque is continuously monitored and recorded throughout the installation of each screw piling. Continuous recording chart recorders are used to measure the hydraulic pressure that is used to drive in the piling. For small shaft piles there is a direct relationship between installation torque and screw pile capacity. Continuous monitoring of torque during installation provides the installer with a profile of the underlying soil conditions.

General Foundation 

Screw pile can deal with various loadings so they can be used in a wide 

variety of load bearing situations. Included are the aforementioned and the 

following: 

  •  Static loads (e.g. under buildings); 
  • Alternating loads (e.g. under pumps jacks);  
  • Dynamic loads such as vibratory loads (e.g. under compressors);  
  • Loads with high moment of overturn (e.g. communication towers);  
  • Grade beams (e.g. in conventional buildings); and 
  • Structural floor slabs. 

Pile Drive is capable of completing projects of virtually any size.  We have produced steel screw piles for projects requiring less than a dozen piles but we also cater to major industrial projects requiring more than 500 steel screw piles. All steel screw piles are individually designed to meet customers’ needs.

Contact us now for your steel screw piling needs.

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