Experimental study on the whole process of instability and failure of anchorage structure in surrounding rock of deep-buried roadway

This paper aims to explore the whole process from initial load bearing to the overall instability of surrounding rock anchorage structure of the deep-buried roadway,and to reveal the evolution characteristics of the internal stress, deformation and fracture of the surrounding rock. Based on the engineering background of -967 m west wing track roadway of Kouzidong coal mine,various large-scale simulation experiments on the deformation,failure evolution char- acteristics,and the bearing capacity of roadway surrounding anchorage structure with no support,bolt support and bolt- cable anchor support were respectively carried out using the self-developed simulation testing system for the whole process of structural instability in deep underground engineering project. The load-displacement curves of the whole process of deformation and failure of the anchorage structures with different supporting forms were obtained through the test. With the increasing supporting strength,the stress drop phenomenon of the load-displacement curves gradually weakens,while the peak bearing capacity,equivalent elastic modulus,and peak displacement increase by 82. 57% , 33. 33% ,and 107. 24% ,respectively. It is easier for the surrounding rock to generate the structural effect of “pressure arch”,and the deformation resistance capacity gradually enhances. During the test,the deformation of the roof is the largest,followed by the two sides,and the floor is the smallest. As the support strength increases,the failure character- istics of the anchorage structure transforms from brittle failure dominated by tension cracks to plastic failure dominated by shear slip. The response characteristics of the multi-source geophysical information have a good coupling relation with the load-displacement curves. With the increase of supporting strength,the number of failure per unit time in the anchorage structure gradually decreases,and both the electromagnetic radiation intensity and number of pulses gradual- ly weaken. The acoustic emission events exhibit a good corresponding feature with the crack initiation and development in the anchorage structures. When the model enters the unstable failure stage,with the rapid crack growth,the acoustic emission activity is very active. As the applied load increases,the anchorage structure tends to be loosely broken due to gradual crack development,resulting in gradual increase in the apparent resistivity while gradual decrease in the re- gional conductivity. With the increasing supporting strength,the formation time of high resistance zone in the anchorage structure becomes larger but the range becomes smaller.