Rehabilitation of Mining Sites using Geogreen Erosion Control Blanket®: A Sustainable and Cost-Effective Technology

Abstract

Rapid industrialization and urbanization are imposing a drastic toll on the consumption of all natural resources. One such resource ignored by most infrastructure and industrial sectors is the development of green cover and ecological balance by the protection of barren slopes, which eventually undergo erosion and become unstable. Either the lack of vegetative cover from the slopes or the instability of the slope leads to its sliding. Reclamation and Rehabilitation of the existing mined areas is essentially the most supreme performance evaluator of any mining company. This is a personal and national responsibility, and one must make sincere efforts to strive towards preserving Mother Earth. Conventionally, methods involve the use of stone pitching and concreting to protect such slopes, in turn harming the environment by stone quarrying. Bio-engineering methods are preferred over these conventional methods due to their low cost and lower maintenance requirements. This incorporates stabilizing the slope by applying a suitable blanket cover to prevent future sliding and further adding vegetation to it so that it acts as a carbon sink. The huge amount of vegetation that grows enables large amounts of carbon sequestration. One such product is the Geogreen blanket developed by Sri Venkateshwara Fibre Udyog Private Limited, Bengaluru has a strong and excellent team of R and D department and has been a pioneer in making coconut fiber husk-based products for the last twenty-three years. The Geogreen blanket is eco-friendly as it is made from naturally available biodegradable coconut fibers. The product is eco-friendly, it has a high amount of lignin content, which makes it resistant to insects, molds, and rot. Its main merit is that it can retain moisture for a long period; it helps in the growth of vegetation, thereby making these barren slopes beautiful. Being frugal and self-sufficient, it is strong enough to be used in the most severe climatic conditions and rainfall. It has proved to work successfully in all areas, from the highest rainfall zones to the driest climatic conditions. It has successfully operated on slopes ranging from flatter than 30 degrees to steeper than 80 degrees. The Geogreen blanket is a natural geo-composite self-sufficient in performing technical functions of fluid transmission, filtration, separation, reinforcement, and protection. It can be modified to meet the site conditions and suitable requirements. It is not only easy to install but can be installed with a limited number of unskilled labor and conventional tools. Its ease of installation makes it very suitable for inaccessible areas, too. The Geogreen blanket possesses the exclusive property of providing suitable strength over time as the roots grow further, entangling with each other, thereby increasing its structural stability. Especially in the case of those areas that have less access, this method proves to be compatible enough under all circumstances. The product is versatile, has very wide areas of application potential, and is one of the most evolving methodologies of the future. Till now, this material has been able to sequester a huge amount of carbon dioxide and produce a carbon sink of around 21.53 tonnes per hectare by the technique of using a Geogreen blanket. Several prominent reality and infrastructure companies have contributed to ecosystem preservation by adopting this methodology. Hence, it is highly recommended to use this eco-friendly and economical technique and play our part in conserving nature in the long run.

1) Introduction

Urbanization and industrialization have taken a massive toll on the health of our wealthy deposits of natural resources, such as land, water, and air.  The expansion of any nation in terms of its economic growth and infrastructure development involves an enormous scale of engineering and construction, including roads, bridges, and highways, riverbank development, railways, mining projects, industries, etc. This has generated several cut-and-fill slopes in many places (Yang et al., 2016). The protection of such slopes thereby becomes the responsibility of the people involved in the execution of such projects. The most vital and intricate part and parcel of surface protection of the earth is to maintain the stability of slopes by preventing landslides and soil erosion.

Several large-scale projects of mining and processing ores and minerals occupy huge amounts of land. These give rise to several waste overburden dumps at the end of the project (Kondracka et al. 2021). Such waste dumps consist of accumulated particles of waste metal and minerals and are often non-fertile and prone to erosion. Erosion of such slopes can be activated by different modes. These constitute external forces, mainly the action of wind (air-borne), the action of water, and vibrational forces, while internal forces include the moisture level. Zhuang et al. (2009) stated that there are several trace elements present in such waste dumps that are activated up to large distances by the airborne transfer of metal-bearing minerals, runoff at surface level, and the percolation of rainwater into the ground, contaminating groundwater and soil.

It is observed in past studies or research work that in a large number of situations, the erosion of such overburdened mining dump slopes is brought about by an imbalance in the internal moisture level of the dump particles. When the moisture level in such mining slopes is too high, the particles of the dump start falling by themselves, when the dump exceeds a certain height.  On the contrary, when the internal moisture level is very low, they do not possess sufficient properties of shear strength to hold themselves against external forces. Hence, erosion is bound to occur in both cases. Erosion and spreading of such non-fertile, metal, and mineral phase particles, which are deficient in nutrient value and suitable pH over the surrounding fertile soil, disrupt the fertility of that soil and make it worthless for agricultural purposes. Due to these reasons, a sufficiently huge amount of topsoil has been lost till now.

This explains the urgency and significance of preventing erosion on such mining overburden dumps and protecting such slopes. Different conventional mechanisms of slope protection methodologies have been tried and tested for a long time. Whenever a particular type of slope protection technology is being implemented, it becomes detrimental to maintain a balance between the successful performance of the technique and the preservation of the environment at the same time. Some of the past studies on mechanical means of slope protection include the application of riprap, stones, concrete slabs, sizing blocks, or flexible meshed concrete slabs, to enhance slope protection by providing attributes of mechanical strength (Luo et al., 2018; Li et al., 2019; Yao et al., 2019, 2020; Wan et al., 2019; Lin et al., 2019). If the design of slope protection measures is done by keeping in mind its ecological performance, then this can enable the modification and improvement in the mechanical properties of the slope as promulgated by Cao et al. (2018); and Tang et al. (2018). Therefore, it is of utmost necessity to balance mechanical and ecological properties in the context of slope protection.

One of such measures taken for safeguarding the slopes is the use of bioengineering technology. Bio-engineering methods are preferred due to their low cost and lower long-term maintenance. It possesses the exclusive property of providing inherent strength over time as the roots grow further, entangling with each other,r thereby increasing its structural stability. Sri Venkateshwara Fibre Udyog Private Limited aims for sustainable development. They have been achieving this for the last twenty-three years with almost a hundred percent success rate through the means of rigorous R&D, precise manufacturing, development, and the application of several segments of the eco-friendly product range. Sri Venkateshwara Fibre Udyog Private Limited works on the reclamation and rehabilitation work of several mining project sites to date using their Geogreen Erosion Control Blanket®. It is made from naturally available coconut fibers bonded by resins. Moreover, it is eco-friendly and biodegradable as it has a high amount of lignin content, which makes it resistant to insects, molds, and rot.

Its main merit is that it can retain moisture for a long interval of time. Once the vegetation starts, the porosity of this upper layer increases, and it helps in the growth of vegetation. In a way, it converts the subgrade soil into topsoil. The roots of these vegetated species get entangled with each other and provide support in holding the GECB and making these restored areas beautiful. Numerous research efforts by Coutts (1983; Cucchi and Bert 2003), Mickovski and Ennos 2003), Nicoll et al. 2006), and Chiatante et al. 2010 have also concluded that the roots of plants greatly increase the shear strength of soil, reducing the stress concentration, improving the soil stress of shallow slopes, and improving slope stability by strengthening the surface of soil.

     GECB is cost-effective and self-reliant. This paper serves as a medium to acknowledge this novel methodology of mining slope protection and erosion control. The authors have tried their best to disseminate maximum information regarding this unique and environmentally-friendly technology in the subsequent chapters of this paper.

2)    Materials and Methodology

The state-of-the-art bioengineering technique of geogreen blankets is a natural geo-composite self-sufficient in performing technical functions of fluid transmission, filtration, separation, reinforcement, and protection. It can be modified to meet the site conditions and suitable requirements. It is not only easy to install but also done with a limited number of unskilled labor and conventional tools. Its ease of installation makes it very suitable for inaccessible areas.

     There is a huge amount of erosion on the slopes of mines due to the above-discussed reasons and factors. Either the lack of vegetative cover from the slopes or the instability of the slope leads to its sliding. This can be prevented by stabilizing the slope and further adding vegetation to it to prevent future sliding and failing by applying a suitable blanket cover. This material can be applied to all the slopes that are adjacent to roads and railways, as well as in safeguarding the already mined areas. Restoration of open-cast mines can be done by the use of a geogreen blanket. It can be applied to steep vertical slopes as well as horizontal slopes. The following denotes the standard methodology that has been researched and developed by the team of Sri Venkateshwara Fibre Udyog Pvt. Ltd. to be followed for the installation of a geogreen erosion control blanket for slope stabilization.

• Step I - Preliminary investigation of the site

• Step II - Site preparation

• Step III - Installation of the Geogreen Blanket

• Step IV - Vegetation Development

• Step V - Maintenance
  

3) Results

4) Conclusions

The rehabilitation project work of several kinds of mines, including cast iron ore mines, coal mines, and precious metal quarries, has been successfully executed by using Geogreen Erosion Control Blanket®. Geogreen Erosion Control Blanket® is made from bio-degradable coconut fiber husks. It is an environment-friendly, economical, and long-term maintenance-free solution for the protection and stabilization of slopes.

The methodology for laying the Geogreen Erosion Control Blanket® is simple, quick, and requires fewer workers. After completing the preparations of the site, it is covered with suitable organic soil conditioner or cow dung manure. This is followed by the pre-requisite work consisting of the trench work, chute-drain, berm, and kerbstone, and finally, the Geogreen Erosion Control Blanket® is installed. The blanket is anchored suitably with hooks, and the required overlapping is maintained. Finally, the broadcasting of the selected variety of seeds is done, and the slope is provided with watering either using seasonal rainfall or artificial irrigation methodologies for the vegetation development.

The results obtained by this technique protect the slope against hazard, damage, and pollution problems with the added advantage of increased green cover and carbon sequestration. This novel material has been able to sequester a huge amount of carbon dioxide and produce a carbon sink of around 21.53 tonnes per hectare. It proves to be an ideal solution for supporting the slopes in different ranges of heights, preventing them from getting carried away and protecting them against sliding and other effects. It adds new life to the slopes and embankments in terms of blooming green vegetative cover. It reduces vehicular pollution on highways and lowers the carbon footprint.

The dense vegetative cover on the surface of GECB enables the increase in porosity of the upper layer, therefore converting the subgrade soil into topsoil. It helps in adding to the green cover and reduces the carbon footprint.  It proves undoubtedly suitable for preventing the erosion of soil and protecting it against sliding and other effects. It is also self-sufficient in terms of required repair and maintenance. It adds new color and life to the slopes and

Acknowledgments

The authors are thankful to Vedanta Limited, Sesa Goa Iron Ore- Chitradurga, Karnataka for giving this project of mining site reclamation, and the team of Sri Venkateshwara Fibre Udyog Pvt. Ltd. for developing research facilities for performing all the research-related experimental work.

Declarations

 The authors state that they have no competing interests.

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