Influence of Flaw Inclination Angle on Unloading Responses of Brittle Rock in Deep Underground

Abstract

Excavation unloading is a primary stress condition for engineering rock mass in deep underground. Based on the unloading stress condition during the excavation operation, this paper employed a distinct element method (DEM) to simulate the unloading responses of intact and preflawed rock specimens. The simulation results revealed that the unloading failure strength, unloading damage thresholds, and cracking characteristics were largely dependent on the inclination angle α of the preflaws. With the increase in the flaw inclination angle, the unloading failure strength of a preflawed specimen exhibited a sigmoidal curve increasing trend, and it decreased by 5.5%-20% compared to the unloading failure strength of an intact specimen. Based on the crack accumulation in specimens, three damage thresholds were identified under unloading condition and two damage thresholds σci and σdi were found to be increased with the increase in the flaw inclination angle. Furthermore, when the flaw inclination angle was smaller, cracks were initiated around the preflaws, and there were obvious axial splitting cracks in the failure modes of preflawed specimens, while axial splitting cracks were few in the preflawed specimen with a larger flaw inclination angle and none in the intact specimen. These unloading responses indicate that inducing preflaws can reliably reduce the unloading failure strength and promote the cracking process of hard rock during an excavation unloading process. Moreover, inducing preflaws with a smaller inclination angle (e.g., vertical to the unloading direction) will be more helpful for the unloading failure and rock cracking during an excavation unloading process.

Failure mechanism and stability analysis of an open-pit slope under excavation unloading conditions

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Loading Behavior and Soil-Structure Interaction for a Floating Stone Column under Rigid Foundation: A DEM Study

“…The DEM is widely used in geotechnical engineering, such as slopes, embankments, roads, and rocks [36][37][38][39][40][41][42][43][44][45][46]. In geotechnical engineering, DEM can simulate the discontinuity of soil and rock and reveal the microscopic failure mechanism.…”

Researches on Crack Propagation of the Two Filled Noncoalescent Coplanar Flaws under the High Strain Rate Loading by means of AUTODYN-Based Simulation

“…Deep underground civil engineering construction such as energy resources exploration and subway construction have given rise to large scale research done on in-depth rock mechanics [1,2]. Underground rock masses contain a large number of structural planes such as cracks, joints, and bedding planes with different sizes, which are frequently affected by tectonic strain and engineering disturbance [3].…”