Abstract
In order to study the fractal characteristics of the pomegranate biotite schist under the effect of blasting loads, a one-dimensional SHPB impact test was carried out to test the dynamic compressive strength, damage morphology, fracture energy dissipation density, and other parameters of the rocks under different strain rates; besides, sieve tests were conducted to count the mass fractal characteristics of the crushed masses under different strain rates to calculate the fractal dimension of the crushed rock D . Finally, the relationships between fractal dimension and dynamic compressive strength, crushing characteristics, and energy dissipation characteristics were analysed. The results show that under different impact loads, the strain rate effect of the rock is significant and the dynamic compressive strength increases with the increasing strain rate, and they show a multiplicative power relationship. The higher the strain rate of the rock, the deeper the fragmentation and the higher the fractal dimension, and the fractal dimension and rock crushing energy density are multiplied by a power relationship. By performing the comparative analysis of the pomegranate biotite schist, a reasonable strain rate range of 78.75 s-1~82.51 s-1 and a reasonable crushing energy consumption density range of 0.78 J·cm-3~0.92 J·cm-3 were determined. This research provides a great reference for the analysis of dynamic crushing mechanism, crushing block size distribution, and crushing energy consumption of the roadway surrounding rock.
Highlights
The dynamic hazard is very frequent in the deep mining project [1, 2], and many scholars think that the fracture pattern is critical to studying the rock fractal in the mining, underground geotechnical engineering blasting, and other fields [3,4,5]
The typical tunnel envelope rock, pomegranate biotite schist, was selected to carry out section Hopkinson pressure bar (SHPB) rock dynamic mechanical tests, and rock fragmentation characteristics under different strain rates, strength indexes, and energy parameters were obtained to establish the relationship between fractal dimension and these parameters
This research provides a reference for further study of the dynamic mechanical properties of pomegranate biotite schist in deep mining and provides guidance for the optimisation design of blasting parameters for underground mine tunnelling
Summary
The dynamic hazard is very frequent in the deep mining project [1, 2], and many scholars think that the fracture pattern is critical to studying the rock fractal in the mining, underground geotechnical engineering blasting, and other fields [3,4,5]. As one kind of typical rock in the deep mine roadway envelope, with fractal theory, the fractal evolution of crushed pomegranate biotite schist under impact loading was studied, and the relationship between its fractal dimension and the strain rate, dynamic compressive strength, average block size, and crushing energy dissipation density was analysed, which is of great importance to blasting mining, hydraulic fracturing [6,7,8], and liquid CO2 fracturing [9]. The present studies about the rock dynamics test mainly focus on the distribution of rock fragmentation bulk and energy dissipation; the relationships between fractal dimension and impact loading strain rate, average bulk, kinetic parameters, and energy density are rarely studied. In this paper, SHPB kinetic tests and sieve tests were conducted on the pomegranate biotite schist, and the fractal dimension D was calculated using the G-G-S fractal model
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