Dynamic Split Tensile Strength of Basalt, Granite, Marble and Sandstone: Strain rate dependency and Fragmentation

TL;DR

This study investigates how strain rate affects the tensile strength and fragmentation of four different rocks, revealing that secondary fragment sizes are highly strain rate dependent and follow a power law relationship.

Contribution

It provides new insights into the strain rate dependency of rock fragmentation and strength, especially for secondary fragments, across different lithologies.

Findings

Dynamic strength increases with strain rate in agreement with theoretical models

Secondary fragment size strongly depends on strain rate across all tested rocks

Marble and sandstone produce more pulverized debris than basalt and granite

Abstract

The scope of this study is to understand the strength behaviour and fragment size of rocks during indirect, quasi-static, and dynamic tensile tests. Four rocks with different lithological characteristics namely, basalt, granite, sandstone and marble are selected. The Brazilian disc experiments are performed over a range of strain rates from 10-5 /s to 2.7x101 /s using a hydraulic loading frame and a split-Hopkinson bar. Over the range of strain rates, our measurements of dynamic strength increase are in good agreement with the universal theoretical scaling relationship of Kimberley et al. (2013). Dynamic fragmentation during a split tension mode receives very little attention and not much information is available about the generated fragment size distributions. The fragments fall into two distinct groups based on the nature of failure, coarser primary fragments and finer secondary fragments. The degree of fragmentation is assessed in terms of characteristic strain rate and is compared with existing theoretical tensile fragmentation models. The primary fragment size are less sensitive to strain rate, particularly at lower strain rates. The size of secondary fragment has a strong strain rate dependency over the entire testing range. Marble and sandstone are found to generate more pulverized secondary debris when compared to basalt and granite. Further, it is shown that the mean fragment sizes of primary and secondary fragments are well described by a power law function of strain rate.