Gabion Gravity Retaining Walls
Gabion gravity retaining wall systems are monolithic gravity mass structures and follow standard design methods for gravity retaining walls. The following information is provided by as a design guide to assist Professional Engineers, Government Agencies, Land Developers, and Contractors in the proper design, specification, construction and inspection of Gabion gravity retaining walls.
Gabion walls are constructed with natural stone. As drainage occurs soil particles are deposited into the small voids of the natural stone fill within the Gabion wall allowing for pockets of vegetation to take root.
A flexible double twisted mesh Gabion is designed to settle without fracture and adhere to the ground as scour occurs. Graded fill material ranging from 4"-8" for standard Gabions and 3"-6" for reno mattresses will ensure uniform flexibility of the apron and will create a new state of equilibrium of the structure once settlement has occurred providing continued stability. Gabion aprons are commonly used to protect the toe of a Gabion retaining wall structure from scour that could cause undermining in channel works applications. It is recommended that the Gabion apron be a minimum of 9"-12" in depth. The length ofthe Gabion apron shall extend beyond the toe of the structure a minimum of 2 times the anticipated depth of scour. This will ensure that the Gabion apron reaches just beyond the outer limit of the anticipated scour hole that may form.
The Gabion apron will require minimal excavation and grade work. Generally the Gabion apron is placed directly on the ground utilizing a geotextile filter fabric between the Gabion apron soil interface to prevent and leaching of soils from underneath the apron. If the Gabion apron is placed in relatively deep water, and efficient method of large scale placement is prefabricating the apron on a barge and then launching it into the water. The size of the Gabion apron that can be placed by this method is limited only by the deck area of the barge. Gabions or reno mattresses may also be connected together filled and then placed into the water with a sling arrangement. This method is frequently used for building scour-resisting mats around bridge piers etc. Gabion aprons may be fabricated using Terra Aqua standard PVC Gabion units or with PVC reno mattresses.
It may be ermined, through an investigation and stability analysis, that additional stability of the Gabion wall may be required to achieve acceptable factors of safety for sliding. One option to pursue prior to enlarging the Gabion wall cross section for additional stability is to place the Gabion gravity retaining wall on a 6 – 10 degree batter towards the retained slope. This will require the founding soils to graded and compacted to accommodate for the specified wall batter.
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