Executive Summary : | About 70-75% of the total power generated in India is produced by coal-based thermal power plants. India is one of the leading producers of coal fly ash and each year about 40-50% of fly ash remains unutilized. The present generation of fly ash is about 219 million metric tons per annum which are projected to exceed around 900 million tons by 2031-32. The disposal of this un-utilized fly ash creates a bigger challenge for thermal power plants, as it covers around 265 km2 areas as ash disposal sites and predicted that by the end of the year 2020, the total land occupied under ash disposal sites would be around 820 km2 at an estimated rate of 0.6 ha per MW. Generally, wet disposal of ash is the most common practice adopted by coal-fired power stations, and the sedimented ash deposits formed due to the continuous deposition process possess very low density, high compressibility, and poor bearing capacity that are very much susceptible to liquefaction during an earthquake. Also, the leachate, emanating from the ash ponds or lagoons, carries toxic elements and heavy metals leading to contamination of surface water as well as groundwater bodies. However, excavating vast quantities of coal ash from the ash ponds and mixing them mechanically with chemical or mineral admixtures to use it in the field of construction are burdensome and much more expensive. In this context, a suitable laboratory-scale design and experimentation have already been done. Design and field-scale experimentation of various in-situ stabilization techniques are needed to improve the engineering performances (strength and stability) along with controlling the migration of harmful leached elements from the abandoned ash pond sites. It is envisaged to use in-situ stabilization techniques using chemical columns of different specifications along with a combination of pressure injection technique and phytoremediation to large scale laboratory models as well as to real ash ponds and study its efficacy in improving the geotechnical characteristics of the entire ash deposits. However, the amalgamation of Phyto-assisted pressure injection is assumed to hold a higher potential to remove the heavy metal hyperaccumulation and hinder the leaching of contaminants into groundwater. The study also incorporates the characterization of ash leachate and its improvement with the in-situ stabilization methods applied. This technique is presumed as an appropriate sustainable technique to resolve most of the geotechnical problems associated with the huge ash pond sites and make the disposal site suitable for light construction purposes. This whole research proposal is entirely based on United Nations Sustainable Development Goals (UNSDG) number 6, 9, 11, and 15 where the main focus is given on waste to wealth conversion. It will not only manifest sustainability but also highlights the concept of 'Swachh Bharat Abhiyan' (Clean India Mission) |