Gabion

Gabion retaining wall is formed with gabion baskets stacking atop one another, and it plays a positive role in earth retaining, mud-rock flow prevention, slope stabilization, landslide treatment, and soil erosion control, etc.

Gabion retaining walls are regarded as a flexible and free drainage system, which can effectively resist the disturbing forces. During the building of gabion retaining walls, in order to achieve the effect of stability and an aesthetic appearance, it is suggested that the walls should be inclined from the vertical plane by 6 or 10 degrees. The gabion retaining walls' flexibility degree can be determined by the quality of the filling materials, the type of fill, wire diameter of the mesh, and the mesh type. For example, the more angular the filling materials are, the greater care in filling and the heavier the wire diameter of the mesh. Therefore, the requirements on the quality of installation will be higher, thus leading to a more dimensionally stable structure.

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 of the 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 determined, 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.