Abstract
An underground roadway usually contains defects of various types, and when the roadway is subjected to external loading, the locations of those defects influence the roadway by differing degrees. In this study, to study how the locations of defects affect crack propagation in a roadway, specimens with tunnel-type voids were made using polymethyl methacrylate, and the stress wave produced by a bullet impacting an incident rod was used as the impact load. Meanwhile, the variations in crack speed, displacement, and dynamic stress intensity factor during crack propagation were obtained using an experimental system of digital laser dynamic caustics, and the commercial software ABAQUS was used for numerical simulations. From the experiments and numerical simulations, the crack propagation path was verified and the impact fracture behavior of a semicircular-arch roadway with different defect positions was presented. The results show that when the pre-fabricated crack is on the central axis of the sample, the crack propagation is purely mode I; when the pre-fabricated crack is 5 mm from the central axis, the crack propagation alternates between mode I and a mixture of modes I and II; when the pre-fabricated crack is at the edge of the semicircular-arch roadway, the crack propagation follows the I–II mixed mode.
Highlights
Because of the increasing consumption of shallow coal in modern social development, the mining of coal resources has shifted gradually to deep underground spaces
To study how the locations of defects affect crack propagation in a roadway, specimens with tunnel-type voids were made using polymethyl methacrylate, and the stress wave produced by a bullet impacting an incident rod was used as the impact load
The variations in crack speed, displacement, and dynamic stress intensity factor during crack propagation were obtained using an experimental system of digital laser dynamic caustics, and the commercial software ABAQUS was used for numerical simulations
Summary
Because of the increasing consumption of shallow coal in modern social development, the mining of coal resources has shifted gradually to deep underground spaces. Wang et al (2017a, b) studied how an empty hole affected crack movement in a polymethyl methacrylate (PMMA) specimen under impact loading. Liu et al (2020) studied how external impact on a PMMA specimen affected multi-crack propagation. Developments in numerical simulation provide a convenient and effective means of studying how defects influence the dynamic fracturing of media, and especially for predicting mixed-mode crack propagation. Zhou et al (2019a, b, 2020) tested a rock tunnel under heavy hammer impact and studied the variations of crack propagation velocity, path, and other parameters in the tunnel by using numerical simulation and strain gauges. The methods used in the above studies were split Hopkinson pressure bar (SHPB) combined with numerical simulation, explosion combined with caustics, and impact combined with caustics, but there have been relatively few studies of dynamic crack propagation under a uniform stress wave by the caustic method. We use the extended finite-element method of the commercial software ABAQUS to simulate the crack growth process, and we compare the test and simulation results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
