Investigation of the dynamic tensile fracture process of rocks associated with spalling using 3-D FDEM

Understanding the tensile fracturing of rocks under high strain-rate conditions (>20 s⁻¹) is challenging due to experimental constraints. The spalling test has been known as a potential method to measure the tensile dynamic strength in the high strain-rate regime. However to date, the different evaluation methods proposed to interpret the spalling test results yield inconsistent dynamic tensile strength and strain-rate. To understand this inconsistency, a 3-dimensional finite-discrete element method (3-D FDEM), accelerated by general-purpose computing on graphics processing units (GPGPU), is applied to simulate the dynamic tensile fracturing process in the spalling test. The 3-D FDEM simulation results agree with the experimental results in terms of fracture patterns and free surface particle velocity to evaluate the dynamic tensile strength and corresponding strain-rate under various loading rates. The 3-D FDEM simulations can capture the discrepancies in dynamic tensile strength and strain-rate obtained based on the different evaluation methods used in the spalling test. When integrated with experimental analyses, the 3-D FDEM could provide insights, and has potential application in estimating local strain-rate and fracture location, which are key factors for the reliable evaluation of dynamic tensile strength and strain-rate in spalling tests, but are challenging to evaluate by experiments only.