*Article* **Creation of a Nanomodified Backfill Based on the Waste from Enrichment of Water-Soluble Ores**

**Elena A. Ermolovich 1, Alexander L. Ivannikov 2,\*, Marat M. Khayrutdinov 3, Cheynesh B. Kongar-Syuryun 2,4 and Yulia S. Tyulyaeva <sup>2</sup>**

	- <sup>4</sup> Department of Mineral Resources and Process Engineering, Technische Hochschule Georg Agricola (THGA), Herner Street 45, 44787 Bochum, Germany
	- **\*** Correspondence: ivannikov.al@misis.ru

**Abstract:** The paper analyzes losses during the development of low-value water-soluble ore deposits. The importance of development systems with backfill is shown. The use of industrial wastes of water-soluble ores to replace specially produced inert components in the preparation of backfill seems to be a good way to utilize them. The aim of the work was to create a fill mass with improved strength properties based on industrial wastes of water-soluble ores activated with a nanomodifying material. The characteristics (chemical and granulometric compositions) of an aggregate of the backfill based on the waste from enrichment of water-soluble ores are given. The validation of the hardening mixture compositions for various mining systems was carried out considering: the specified strength, the time of the artificial mass erection, the time to achieve the required strength properties of the material, which determine the possible intensity of the mining operations; method of transporting the backfill. The expediency of using a multilayer fulleroid nanomodifier astralene as a nanomodifying additive has been proved. The effect of the backfill activation with a nanomodifying additive, astralene, on the structural changes of halite wastes from the halurgic enrichment of water-soluble ores (potash) was investigated. To study the strength properties of the fill mass, the comparative analytical method was used. The strength properties of the backfill were measured in standard test periods, taking into account the intensity of hardening of the backfill material (after 7, 14, 28, 60, 90 days). To obtain reliable results, 10 backfill samples were tested at each of the scheduled dates. The shape and chemical composition of crystalline new forms were studied. Studies were performed using X-ray phase analysis and scanning electron microscopy. As a result of uniaxial compression of hardening backfill samples, the dependence of the ultimate strength on the astralene content and the hardening time were established. It has been experimentally proved that the use of a nanomodifying additive, astralene, in the backfill allows an increase in the strength properties of the created artificial mass by 1.76–2.36 times while reducing binder consumption.

**Keywords:** waste from enrichment of water-soluble ores; artificially supported mining method; backfill; activation; nanomodifier astralene; ultimate compressive strength
