Abstract
Indentation hardness and brittleness are the important factors to be considered in the study of rock-like materials’ mechanical crushing behaviors. The brittleness of rock-like materials is defined as the ratio of uniaxial compressive strength to tensile strength in this paper. In order to investigate the influences of hardness and brittleness on rock-like materials’ crushing behaviors, quartz sand and high strength α-hemi-hydrated gypsum were used to prepare rock-like materials with different hardness and brittleness through different mass ratios. The artificial rock-like materials can eliminate the effects of natural rock’s weak structure plane on experimental results. The indentation test, Uniaxial compressive test, and Brazilian tensile test were conducted for characterizing the indentation hardness and brittleness of this artificial rock-like materials. The experimental results showed that brittleness increased with the increase of indentation hardness with high correlation coefficient. The confining stress presented a positive impact on the indentation hardness of the rock-like materials. Based on those mechanical properties, the numerical rock models were calculated to study rock crushing behaviors using discrete element method (DEM). A series of rock crushing tests were conducted to investigate the influences of hardness and brittleness of rock-like materials on rock crushing behaviors using a conical pick cutter. The numerical results showed that the normalized specific energy was negatively correlated with indentation hardness index (IHI). The normalized specific energy decreased with the increase of brittleness index (BI) with a high correlation coefficient. This study is beneficial in utilizing IHI and BI to evaluate the mechanical properties, failure patterns, and mechanical crushing efficiency of rock-like materials.
Highlights
Understanding of rock hardness and brittleness has a crucial importance for practical underground construction engineering. e correlation between hardness and brittleness of rock materials and their mechanical properties and failure patterns has been the focus of research hotspot in related fields
The crushing models are calculated based on the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) of the rock-like specimens. e cutting force and Specific energy (SE) during fragmentation and failure patterns were investigated. e contribution of this study is that for the first time, the influence mechanism of rock-like materials’ hardness and brittleness on their crushing behaviors and failure patterns is investigated by artificial rock-like materials and discrete element method (DEM). e artificial rock-like materials can eliminate the effects of natural rock’s weak structure plane on study results. is investigation is of great significance for understanding the correlation between hardness and brittleness of rock materials and their fragmentation as well as failure patterns in rock crushing behaviors of underground engineering
Under 5 MPa confining stress conditions, SE is negatively correlated with indentation hardness index (IHI); the normalized specific energy SE decreased with the increase of BII ∗ with a high correlation coefficient of 0.98256, as shown in Figures 22 and 23
Summary
Understanding of rock hardness and brittleness has a crucial importance for practical underground construction engineering. e correlation between hardness and brittleness of rock materials and their mechanical properties and failure patterns has been the focus of research hotspot in related fields. Erefore, hardness and brittleness can be used as the important indexes to Mathematical Problems in Engineering characterize the mechanical properties and failure patterns of rock materials. This paper investigates the correlation between mechanical properties and failure patterns of rock materials and their brittleness as well as indentation hardness based on rock crushing behaviors. E contribution of this study is that for the first time, the influence mechanism of rock-like materials’ hardness and brittleness on their crushing behaviors and failure patterns is investigated by artificial rock-like materials and DEM. Is investigation is of great significance for understanding the correlation between hardness and brittleness of rock materials and their fragmentation as well as failure patterns in rock crushing behaviors of underground engineering The crushing models are calculated based on the UCS and BTS of the rock-like specimens. e cutting force and SE during fragmentation and failure patterns were investigated. e contribution of this study is that for the first time, the influence mechanism of rock-like materials’ hardness and brittleness on their crushing behaviors and failure patterns is investigated by artificial rock-like materials and DEM. e artificial rock-like materials can eliminate the effects of natural rock’s weak structure plane on study results. is investigation is of great significance for understanding the correlation between hardness and brittleness of rock materials and their fragmentation as well as failure patterns in rock crushing behaviors of underground engineering
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