Abstract
The integrated disposal of surface subsidence pits and surface solid waste can be realized by backfilling a surface subsidence area with a paste made from the solid wastes of mines, such as tailings and waste rock. The microstructures of these wastes determine the macroscopic properties of a paste backfill. This paper presents an experimental study on the internal structure evolution of pasty fluid mixed with different waste rock concentrations (10%, 30%, and 50%) and cement dosages (1% and 2%) under damage. To this end, a real-time computed tomography (CT) scan is conducted using medical CT and a small loading device. Results show that UCS (uniaxial compressive strength) increases when the amount of cement increases. Given a constant amount of cement, UCS increases first and then decreases as waste rock content increases. UCS is maximized at 551 kPa when the waste rock content is 30%. The paste body is a typical medium used to investigate initial damage, which mainly consists of microholes, pores, and microcracks. The initial damages also exhibit a high degree of random inhomogeneity. After loading, cracks are initiated and expand gradually from the original damage location until the overall damages are generated. The mesostructure evolution model of the paste body is divided into six categories, and this mesostructure is reasonable when the waste rock content is 30%.
Highlights
Surface subsidence is a sudden or sustained fall caused by mining, groundwater exploitation, and seismic activities
Waste rock and other solid wastes are commonly used to backfill inactive surface collapse pits or open pits directly
No safe and effective disposal method has been developed for surface subsidence in the active phase [4,5,6]; that is, dozens of surface collapse pits are formed in the Tong-keng mine in Guangxi Province as a result of decades of underground mining, and these surface subsidence areas remain active
Summary
Surface subsidence is a sudden or sustained fall caused by mining, groundwater exploitation, and seismic activities. This type of geological disaster can induce serious damages [1,2]. During the long-term production process, a large number of solid waste dumps, such as tailings and waste rock, accumulates on the mine surfaces These mine tailings and waste rocks are mixed and formed into a paste to achieve the integrated disposal of surface subsidence pits and surface solid waste through backfilling. Present study adopts scanning technology to investigate the microstructure investigateofthe microstructure of mixed paste in the damage process.
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