法向应力对煤充结构体界面剪切行为的影响OA

Interfacial shear failure is one of the typical instability modes for coal-backfilling structures.The normal stress has an important influence on the interfacial shear mechanical behavior of coal-backfilling structures.In this paper,single-sided shear tests were conducted on coal-backfilling structures with serrated interfaces at five normal stress levels:0.6 MPa,1.2 MPa,1.8 MPa,2.4 MPa,and 3.0 MPa.Moreover,the interfacial shear mechanical properties of the coal-backfilling structure were analyzed,and the influence of different normal stress levels on the failure mode and stress state of the coal-backfilling structure interface was studied.Finally,a theoretical model was established to describe the climbing,cutting,and slip failure of the coal-backfilling structure interface under shear loading.The following research results were yielded:The interfacial shear strength of the coal-backfilling structure increases linearly with the growth of normal stress.The rise of normal stress alters the interfacial stress distribution of the coal-backfilling structure,resulting in differences in the final failure mode.At a low normal stress level,climbing failure occurs when the load on the interface sawtooth exceeds its shear strength.With the growth of normal stress,cutting failure occurs when the load on the sawtooth end of the coal element or the backfill element exceeds its shear strength.Slipping failure eventually occurs when the load on the overall interface exceeds its shear strength.The proposed theoretical model for interfacial shear failure can effectively predict the shear strength corresponding to the three failure modes of the coal-backfilling composite structure.