A Preliminary Study on the Improvement of Gangue/Tailing Cemented Fill by Bentonite: Flow Properties, Mechanical Properties and Permeability

Abstract

Backfill mining has significant advantages in safe mining, solid waste utilization and ecological environmental protection, but solid waste materials (tailings, gangue and coal gasification slag, etc.), as derivative residues of the chemical and metallurgical industries, contain a large number of heavy metal elements, which is posing great challenges to the underground environment after backfill. In order to study the feasibility of bentonite for reducing the permeability of gangue/tailing sand cemented backfill body, relevant tests were carried out from the basic performance index, flow performance and mechanical properties of paste backfill materials. The test results show that bentonite has a significant effect on the water secretion rate of cemented fillers, and also promotes the improvement of slump and diffusion diameter of backfill slurry. The enhancement effect of mechanical properties in the early stage is not obvious, mainly concentrated in the middle and late stages of specimen curing. With the increase of bentonite content, the 28-day uniaxial compressive strength increased from 7.1 MPa and 7.9 MPa to 8.7 MPa and 9.0 MPa, respectively. Bentonite is filled between the pores of the cemented backfill with its fine particles and water swelling, which can reduce the porosity and permeability of the gangue and tailings cemented backfill. Therefore, on the premise of satisfying the flow and mechanical properties of paste backfill, bentonite can be used to improve the permeability of cemented backfill and reduce the leaching and migration of heavy metal ions.

Numerical Study of Gangue Slurry Deposition Behavior in Pipelines Considering Viscosity Change

“…In pipeline transportation, the longer the time duration, the greater the slurry's viscosity. According to the measured values of the viscosity of gangue slurry at different times [2,11,18], the trend of gangue slurry with time and its fitting curve can be obtained and is shown in Figure 4.…”

“…However, the physical properties of gangue particles, such as particle size and shape, will affect the fluidity of gangue slurry in the pipeline. Changes in fluidity increase the number of settled particles, resulting in pipeline clogging during slurry transportation [11][12][13]. The clogging of the grouting pipeline will cause economic losses and delay the progress of the filling project.…”

“…Suppose that the viscosity of the slurry is too low. In that case, stratification and segregation can quickly occur and many particles settle, resulting in pipeline clogging in the slurry transportation process [9,11,20]. However, the research at this stage does not consider the influence of the viscosity change of the slurry on the rule of motion of the coal gangue slurry.…”

Assessment of Unfrozen Water Content in Copper Bentonites Using the 1H NMR Technique: Optimization, the Method’s Limitation, and Comparative Analysis with DSC

“…Bentonites, due to their unique adsorptive properties, have found widespread applications in various fields, such as construction, engineering, environmental protection, medicine, and the food industry [1][2][3]. In the context of environmental protection, bentonite is frequently used as a sealing barrier in landfills and wastewater treatment plants.…”