Experimental Study on Mechanical Properties and Anchorage Performances of Rock Mass in the Fault Fracture Zone

The mechanical properties and anchorage performances of rock masses are important to the success of underground engineering in fault fracture zones, but the impact of the rock block size and cementing strength on these properties and performances is unclear. A set of laboratory methods was developed to simulate the development of rock masses in fault fracture zones. Next, model specimens were prepared from natural rock blocks of different sizes and cementing materials of various strengths, and an aluminum alloy bar was installed as a model bolt to fabricate anchored model specimens. Compared with natural rock samples, the fault fracture rock mass exhibited a clear degradation in its strength and deformation parameters, and the degradation coefficients ranged from 19.20 to 86.51%. Under an applied axial load, as the rock block size or cementing strength increased, the mechanical parameters, including peak strength and elastic modulus, for both anchored and nonanchored model specimens increased from 16.90 to 69.05%. Because of the anchorage performance of the bolt, the anchored model specimens presented larger mechanical parameters than those of the nonanchored models. The effective anchorage strength of the bolt was found to be generally stable as the rock block size increased, but it decreased with the cementing strength. The ultimate failure modes of the anchored models with smaller aggregate sizes or lower cementing strengths were found to be characterized by cracks propagating along the cementing surface. For models with a larger rock block size or higher cementing strength, crack development throughout the intact rock blocks was also observed. (C) 2018 American Society of Civil Engineers.