Mechanical Behavior and Failure Mechanisms of Roadway Surrounding Rock Evolving With Distance: A Study on Stress Gradient Paths

ABSTRACT Surrounding rock of the roadway is subjected to complex stress conditions of approximately circumferential unloading and axial loading after excavation. Core sampling can reveal the broken state of the rock near the roadway and the relatively intact condition far from the roadway. It is difficult to further characterize the range and characteristics of the surrounding rock in different areas. Based on the loading conditions and history of the surrounding rock, this paper proposes the surrounding rock disturbance equivalent model. Based on the model, a simplified loading‐unloading path was designed to gradually approach the stress state of the actual surrounding rock. Homogeneous sandstone was selected as the research object. A stress gradient path loading test was carried out mainly by numerical simulation and further verified by laboratory tests. The results show that under the action of the stress gradient, the strength of sandstone is higher than that under conventional conditions, and it has a significant accelerated brittleness effect. The closer to the roadway, the stronger the stress gradient characteristic becomes, and the rock transitions from ductility to brittleness. The stress changes and failure modes of the sandstone were observed by means of simulation and experiments, and the expression form of the boundary range of the transition zone was calculated. The results are in good agreement with the theoretical concept of the simplified stress gradient field model. This indicates that that using the stress path to simplify the surrounding rock is of reference significance.