Experimental Study on Deformation and Acoustic Emission Characteristics of Arch Roadway under Different Unloading Rates

Abstract

The essence of roadway excavation is a process of unloading at the periphery, and the influence of unloading paths on surrounding rock damage is directly related to the selection of support design and construction technology. The real stress state of surrounding rock is often affected by different excavation conditions in the actual construction process. Therefore, a testing system of excavation and unloading model was developed to simulate the unloading process of the arch roadway under different excavation conditions. Small hollow cylindrical specimens used in this experiment were made of cement mortar. The load at the inner cavity of specimens was removed under the constant action of external pressure and axial force to simulate the real excavation unloading process. The deformation, the failure modes, and the acoustic emission evolution characteristics at the inner of specimens were obtained under unloading conditions using the strain and acoustic emission monitoring systems. The experimental results indicate that deformation laws of surrounding rock were similar under different unloading rates and initial geostresses, but failure modes and acoustic emission characteristics were quite different. Compared with that of slow unloading, the damage of surrounding rock under rapid unloading mainly accumulated after unloading, and it is easier to induce rockburst after unloading. As initial geostress increased, the occurring time of the main fracture may be delayed relatively, and the phenomenon that the distribution range of peak frequency expanded and the amplitude rose gradually can be regarded as the precursor information of the main fracture occurring. This study can be used to provide experimental support for the failure and supporting design of surrounding rock in deep underground engineering.

Multifield Coupling Mechanism of Unloading Deformation and Fracture of Composite Coal‐Rock

“…Figure 2 shows the axial stress-time curve of coal and rock. After a full investigation and under the condition that the simulation results are not false, this paper selects the commonly used slow unloading confining pressure rate of 0.03 MPa/s and confining pressure value of 3 MPa [38,39]. e three-axis loading and unloading of composite coal are divided into five stages: 0-2 s is a three-dimensional stress loading stage.…”

Variation Law of Infrared Radiation Temperature of Unloading Fracture of Composite Coal-Rock

“…(4) Under the simulation conditions in steps ( 1) and ( 2), triaxial loading is carried out again. When the stress reaches 80% of the peak intensity recorded in step (3), under the condition of ensuring that the simulation results are not distorted, three commonly used slow unloading confining pressure rates of 0.003 MPa/s, 0.03 MPa/s, and 0.05 MPa/s [43,44] are selected for unloading simulation until the composite coal and rock rupture, and the simulation ends. In order to better study the relationship between the unloading fracture mechanics stage of coal-rock and its infrared radiation temperature, the stress change process must first be clarified.…”

Damage and Failure Characteristics of Surrounding Rock in Deep Circular Cavern under Cyclic Dynamic Load: A True Triaxial Experiment Investigation

“…Based on scanning electron microscopy (SEM), Hu et al [17] identified microcracks in the surrounding rock and obtained the fracture characteristics of granite. Dresen et al [18][19][20][21] used the monitoring, statistics, and positioning functions of acoustic emission (AE) signals to study the evolution law of microscopic failure characteristics and achieved good results. In addition, many scholars [22][23][24][25][26] studied the damage and failure characteristics of the surrounding rock by combining model tests and numerical simulation methods.…”