An elevated increase in the global demand for geosynthetics can be partly attributed to an increase in the scale of mines in the past decade.
With last month’s SME Annual Conference and Expo (21-24 Feb) dedicated to all disciplines of mining engineering and ahead of April’s GenAmerica’s 2016 conference, the effects of these geostructures on their surrounding environments is a prime concern to designers.
One of many examples of geosynthetics being able to provide a solution in this application area is the Shu Kongping mine located in Xingshan, a county of western Hubei, China.
Due to the mountainous landscape, some areas of the mine were in need of protection against rockfall and landslides from the accumulation of mineral waste residue in this phosphorite mine. An additional hazard was the risk of flooding and extreme erosion as a result of heavy rainfall on the vulnerable slopes.
The client, Xing Fa Group, required a solution which would protect the landscape and infrastructure against these potential hazards, while also encouraging the establishment of natural vegetation.
Embracing sustainability, Maccaferri was able to work with the project team to propose ‘green’ environmental solutions to meet the clients’ requirements, while also satisfying the rehabilitation of the mine nature.
Maccaferri proposed Gabion mass gravity retaining walls as a solution to both retain the unstable slopes and also to channel the watercourse and run-off water. At the toe of the gabion wall the hydraulic forces in the channel could cause erosion and possibly undermine it. Therefore, the gabion wall was built upon a scour protection apron of Reno Mattress®, providing a robust and long-term channel lining.
Being free draining, gabion walls do not allow pore-water pressures to build up behind them. This is an ideal capability when used in water courses, or where there is ground water movement.
Higher on the vulnerable slopes, the three-dimensional reinforced geomat, MacMat® R, was used to increase the soil’s resistance to erosion and also provide an environment that enhances the growth of vegetation through the mat.
Where required by the slope re-profiling, Green Terramesh® soil reinforcement was installed to strengthen the soil and to encourage a lush vegetative finish; an important feature of Green Terramesh and requirement of the client.
Green Terramesh is an environmentally friendly modular system with the added benefit of being more rapid to install than traditional soil reinforcement systems. All components of the unit are factory fitted including face reinforcement, erosion control blanket and bracing struts to support the face at the right face angle. These components minimise assembly and installation time for contractors.
The gabion retaining walls and Reno Mattress were delivered to the site flat-packed, assembled and then filled with stones to form flexible and permeable channel linings for erosion control.
That they were able to be filled with site won rock fill, removed the need to import stone fill material and, therefore, reduced truck movements in the surrounding area. This approach reduced the carbon footprint of the solution significantly.
Additional advantages of using steel wire double-twist mesh gabions, Reno Mattress and Green Terramesh are that they are flexible and allow differential settlements and movement without sustaining damage, essential in this challenging environment.
MacMat R and Green Terramesh provide a stable environment to re-establish vegetation and assist in the rehabilitation of the mine to the environment.
And the Galmac / PVC coated mesh ensures the long-term use is not compromised by chemical, biological or environmental degradation.