Case Studies
Bridge fixed in Rivonia, Johannesburg.
Take a look at the full article in the Fourways Review Newspaper.
Gabion Walls Used In Mining
We have just added new photo’s of the gabion walls installed on the Steelpoort site, constructed by Steffanutti and Bressan at Asa Metals. This shows the useage of gabion walls in mining operations and makes the reason self evident for the increasing use of Gabion Baskets in the mining industry. Please also contact us for any further information required.
Gabion Road Retaining Walls – Sabie
The gabion walls along the road near Sabie in Mpumulanga are now almost complete, there are four walls in total with various lengths. The first retaining wall is 4 metres high and is used to retain the cutslope-embankment, reduce water velocities off the tailings slope and act as a rock catch wall for silt and rock/debris coming off the cut slope, thus preventing this material falling onto the roadway.
The second gabion wall below the roadway(halfway up the fill slope) will prevent lateral movement of soils from next to and below the roadway. Thus reducing the risk of roadway settlement and failure, we assisted with the supply of gabion materials, geotextile and toolsets to site. When the work started we assisted the contractor with the on-site gabion training during initial erections which went off well in the end and made for rapid erection and skills transfer on site. This gabion project should be complete by end October 2009.
Please view the rock spoil photo below and note the reason that most gabion contractors allow for about 30% waste or fines in the rock costing calculation, as this finer material generally cannot be used inside the gabion container as the rock size is to small or consists predominently of finer material.
We suggest the use of gabions tool sets to improve gabion installations on sites, our gabion frames shown in the photo below allow for better basket shape once filled correctly. The baskets should be tensioned horrizontally or vertically before the filling process takes place, the tension direction is dependant on whether you have an external horrizontal or vertical mesh direction. Please contact us for further explanation regarding this interesting concept. All gabion walls generally use a geotextile behind and below the wall to reduce fine soil leaching through the gabion wall.
Gabions are a common application in the world and we try to help wherever we can to show how easy they are to be installed on sites using a local unskilled labor force.
The director – Louis Cheyne is shown in one of the photo’s below..!!
Gabion Revetment Wall – Steinmuller, Pretoria West
We have just completed a great looking gabion revetment wall in Pretoria for Steinmuller who do all the steel pipework for Eskom’s mothballed power plants to be re-commissioned in Mpumulanga soon.
The wall designed was originally to a height of 6m with a length of 440m. However funds were short and eventually after cost cutting excercises the final wall was erected to a height of 5m by 105m long. This work was undertaken by about 14persons each day with a TLB to help load the rock quicker from stockpile directly into the baskets, achieving about 1.5-2.0m3 per man per day with machine help to lift the rock to the higher levels. Normally gabion works allow 1m3/man/day for installation purposes. A total quantity of 540m3 of gabion walling was installed on this site. The wall base was founded to a depth of 0.5m passive toe resistance in front of the wall with a pathway in front of it. The gabion facing was rotated into the embankment with a 4degree batter slope to further enhance stability of the wall. The walls base width was 1.5m for the first two gabion levels with subsequent layers of 1x1m. We allowed for a 400mm horizontal step on each level at every one metre change in height.
To reduce time taken to infill the baskets and to reduce rock costing on site a smaller blatfurnace slagment rock was used(from nearby) to infill the rear 67% wide section of the gabion wall. Normal granite rock for the front face was used to provide the neat looking front face evident in the pictures as shown below.
Gabion construction work was undertaken by the highly experienced team of Mr Reg Laskey from Littlecreek Civils – 082-8944155 with Gabion Baskets assisting with initial designs and price estimates and the final supply of gabion, geotextile and geogrid materials to site.
Some photo’s and design drawings are shown below of the works completed, kindly contact us for any further information you require about this interesting project.
Retaining Walls – Steelpoort, 11 July
Asa Metals – Steelpoort.
In late April this year we were appointed by Steffanutti Bressan in Kempton Park as the supplier for the gabions and geotextiles for the site near Steelpoort in Limpopo for the client Asa Metals (Pty) Ltd. Our gabion prices were the best and at the time we were asked to assist the consulting engineer in Midrand with the gabion sectional and layout drawings.
The quantity estimated was aproximately 6000m3 and mass-gravity gabion retaining walls ranging in size from 2m to 8m height were designed, foundation depth about 10% of the height and base width about 50-60% of height, determined by the soil parameters on site. A B.O.Q. was done for the works to determine precise volumes and sizes required to start the installations.
The materials were sent to site in four loads commencing from early May as production proceeded in our gabion production facility. All gabion materials supplied were class A galvanised as per SANS 1580 specification with A4/U24 – 210g/m2, non-woven, Bidim geotextile, layed at all gabion and soil contact faces.
We also provided a skilled gabion contractor to provide an estimate for the labor only component of the installations, together with planned on site plant required and time completion estimates. He was however not used due to the existing prices tendered on the works were lower than his submissions.
The project will now be completed by the end of August 2008 if all goes to plan, I visited site a few times to also advise on the corect installations and provide any other advise necessary to complete the project on time and with the required neatness/quality. Production achieved on this one was about 2.5m3 per man per day, normally contractors allow for 1man per m3 per day.
Gabion Weirs – Matla River Diversion
We supplied the first gabions and mattresses to a site near Delmas in Mpumulanga recently for a series of gabion wers to be built along a river diversion channel. The average width was 5-10m and height to top of berm was 4.8m. The weirs controled the flow of water in the channel to reduced water velocities.
Gabion Baskets assisted the design engineer with a detail for the gabion weirs and mattresses to be installed during late 2007. The contractor AWA Shabugwane Construction is almost complete with the works now, the channel was a length of 11km and was to control the water flow, as a new mine technique had been adopted to mine the coal underground and once complete to implode the tunnels and have the roof fall in to close the mine. This could have caused water flow problems in the valley, thus the reason that the water diversion channel was constructed.
Many gabion weirs have been installed and many more are still to be completed, the works are to be complete by end June this year. All rock and labour was sourced locally and great gabion structures became a reality.
Kindly contact us for further information ralated to this article.
Gabion Weirs – Waterberg, 24 April
Waterberg Golf Estate.
Gabion Baskets were approached recently to assist in the design of water attenuation structures for a river course in a new golf eco-estate to be built near Alma in the Limpopo province. Alma is about 10km from Bela Bela (Warmbaths). The site is to be developed into a 18 hole golf course and eco-estate with game and eco-lodges in the next 5 years. The initial works being done now were part of an insurance claim from floods that damaged some gabion structures and unprotected water couses earlier in the year.
Gabions and mattresses had already been used on site (built last year) and due to poor design and implementation there had been some failure and excessive soil erosion caused by large amounts of rainfall earlier in the year. More extensive soil erosion protection structures were also required.
I visited site with Reg Laskey from Littlecreek Civils in February and we undertook the preliminary design proposals and pricing to complete the works on site. Reg started on site in early March, initially programmed for three months, the works are now to be completed in two months (by the end of April). We were also asked to work with Mr. Helmut Keller a hydraulic design engineer with SKC engineers in Pretoria, who had done the design water flows and had been of technical assistance to the client previously. We met with Helmut and he recommended some modifications to our designs to allow for further protection of the watercourse.
The gabions on site amounted to 1000m3 of galvanised materials with extra mattress works for repairing and repacking existing mattresses not laid correctly, providing for removal of damaged mesh and repacking and replacing of extra rock within the mattress compartments. Contractors often try to level off the mattress tops with smaller flat rock to achieve a flat level surface on the top of the mattresses. This allows strong water flows to remove the finer rock fragments up through the mesh openings and the partial emptying of the mattresses. We found that some oversized rock placed in the mattresses had also been used and this had to be removed and replaced in position. Normally rock of 100mm min. size to 2/3 of mattress depth maximum size is required for this purpose.
Labor related;- 14 trained and 9 untrained laborers were on site for the duration of the works. Reg used the unskilled labor mainly for collecting, passing and filling of the baskets. The skilled installers were used to erect the baskets, lace them, brace and close them and also for the nice/correct packing on the external front faces, this being the most important task to ensure great looking gabions. On-site rock was mostly used to fill the baskets to allow for reduced costs and the blending in of the rock color with the local soil on site.
Repacking of the River (Reno) mattresses that were not correctly installed and replacing their lids. In many cases no cut-offs were installed on the upstream ends of the mattress protections. We designed gabion weirs at specific points along the river course to reduce water velocities and encourage accretion of finer river bed materials upstream of each structure. The water hydraulic energy was now focused at specific points where adequate mattress protection was designed for and placed. River mattresses were placed where there existed the possibility of soil erosion upstream or downstream of weirs and within the gabion stilling basins. A 20-30Mpa concrete 100mm thick capping was placed on all weir crests and the first two metres of the stilling basins downstream, to prevent debris damaging mesh lids during flash flood situations.
Experienced gabion teams were used for the installations and a neat and tidy project was completed in a short space of time relatively economically and environmentally friendly when compared with any other solution. The client (Matkovitch and Hayes) a landscaping and golf course erection company were very happy with the works and like using gabions on their golf course projects due to the environmental benefits of the system. They were also working on a site:- Nondela in the Natal Drakensburg where we have supplied W.B.H.O. Construction with many gabion materials up untill now.
We have shown some project photos below, kindly contact us for any further information you may need.
