Abstract
Under different exploitive conditions, the humidity levels of the backfill stopes are not the same. Humidity greatly affects the strength and microscopic characterization of the backfill. Cemented paste backfill (CPB) specimens were cured using 0, 30, 70% and standard curing (20°C, 99%) under four different humidity conditions. At 28 days, nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) techniques were used to obtain the microscopic features of the CPB specimens. The relationships between the permeability and uniaxial compressive strength (UCS) of the CPB specimens, and the microscopic characteristics of the CPB specimens, were established. The results showed the following: (i) The permeability of the CPB had an exponential functional relationship with its stone powder content. (ii) The stone powder content of CPB and the peak area of the T2 spectrum are negatively correlated with the UCS. However, there was a T2 peak area corresponding to the worst UCS with the same stone powder content. (iii) The peak area of the T2 spectrum showed that the proportion of area of a small pore size was more than 80%, indicating that the pore size was mainly small. The pore diameter of small pores was linearly and inversely proportional to the UCS of the specimens. It can be found that the factors affecting the strength characteristics of CPB include not only the stone powder content, but also the curing conditions of different humidity.
Highlights
A filling mining method has been widely used in metal mining and is playing an important role in the development and use of mining resources
Permeability is a physical quantity used to characterize the ability of porous media materials to transport liquids, obtained by Coates model in Nuclear magnetic resonance (NMR), the size of which determines the quality of the permeability
To be able to drain the moisture in the backfill faster, reduce the stopping cycle and reduce the pressure on the retaining wall and filtering well, the mine needs a suitable permeability of the backfill [23]
Summary
A filling mining method has been widely used in metal mining and is playing an important role in the development and use of mining resources. The backfill used in the cemented filling mining method mainly uses tailings as the aggregate and cement as the cementing material [1]. With the increase of various solid wastes and the high cost of cement, some scholars have done a lot of research on the disposal of wastes, which are mainly used to replace cement as a cementitious material [5,6]. This will reduce the strength of CPB. In order to increase the strength of CPB, a lot of research has been done [7,8,9]
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