What are Welded Wire Form Walls?
Posted on August 24 2017
Wire basket or welded wire form (WWF) walls are becoming more and more common. They come in a variety styles to meet a variety of applications. They can be used to construct a “green” wall covered in ivy or grass. They can be used to provide a stone face wall similar to gabions without the expense of importing large quantities of stone. Or they can be used to construct a cost effective temporary wall. Also known as L-units because of their shape, wire forms work by acting as a facing unit when constructing a mechanically stabilized earthen wall. The face and base of the forms are connected using steel struts that hold the facing unit at 90 degrees by hooking to the top wire and the back wire of the form. While the welded wire form is the facing unit the soil mass is reinforced through the use of primary and secondary reinforcement. Primary reinforcement is comprised of uniaxial geogrid such as Geostar’s GeoGrid line every 18 inches with the length and strength level of the geogrid reinforcement dictated by the design engineer. Secondary reinforcement is used to retain the face and can vary based on the application. The secondary reinforcement options include a fine mesh geogrid such as Geostar’s MG100 for vegetated walls or biaxial polypropylene grid, heavy duty filter fabric, or galvanized wire mesh for stone filled face walls.
The forms and struts are constructed using W4 diameter steel and the forms are 18” tall by 18” deep and 10’ long. The forms have 4” by 4” apertures. There are a variety of benefits in using welded wire forms when constructing an MSE wall. Because of the open face nature of a WWF wall design, the water behind the wall can simply drain through the face reducing the hydrostatic pressure on the facing units compared to a traditional concrete masonry unit. This can allow you to reduce the amount of imported site fill for a project and in most cases can offer significant cost savings versus a traditional block face wall or gravity wall.
Black steel welded wire forms are raw uncoated steel and are used for temporary and vegetated wall applications. The WWF use as a temporary wall is handy when needing to construct a work or staging pad when flat space is in short supply or can be used to make room for temporary access roads. Vegetation facing elements provide a soft and natural look when constructing a wall and should be selected based on the local seasonal requirements. Common types used include ivy and jasmine, or grass seed applied using the hydroseeding process.
Electronically galvanized welded wire forms are made by galvanizing the steel wire before welding at approximately 18 grams per square meter. This is helpful for jobs when constructing a temporary wall that may specify galvanized baskets but do not specify a galvanization level and are not used for a permanent exposed installation.
Hot dipped galvanized welded wire forms are our standard basket construction but are dipped in zinc after welding in accordance with ASTM A123. Hot dipped galvanized forms are most commonly used for stone filled facing elements requiring long term protection and exposure but can be used in vegetated applications as well when required by the design engineer.
As always if you have any other questions please reach out and we will do our best to get you the information you need as quickly as possible.