Influence of FRP restricting on the splitting failure characteristics of coal-backfilling composite structures
BAI Jinwen1，2，3，YANG Xinyu1，2，SHI Xudong1，2，FENG Guorui1，2，CUI Boqiang1，2，#br#
SONG Cheng1，2，WANG Kai1，2，LI Jian1，2
(1. College of Mining Engineering，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China；2. Key Laboratory of Shanxi Province for Mine Rock Strata Control and Disaster Prevention，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China；3. Postdoctoral Workstation，Shanxi Coking Coal Group Co.，Ltd.，Taiyuan，Shanxi 030024，China)
Abstract：The coal pillar-backfilling composite structure jointly bears the stress in the pillar-side backfilling. The interface between the coal pillar and backfilling is the weakest area. The instability of the interface can induce the failure of the composite structure, and fiber-reinforced polymer(FRP) could be applied to enhance interface stability. Three sets of Brazilian splitting laboratory tests were carried out on coal-backfilling composite structures(without FRP wrapping for reinforcement，FRP wrapping for 1 circle and FRP wrapping for 2 circles) with different interface angles. The DIC and acoustic emission monitoring techniques were used to study the characteristics of the specimens. The results show that：(1) When the load on the interface exceeded the interface tensile or shear strength，interface cracks occurred；the load exceeded the tensile strength of the coal or backfilling element，resulting in tensile cracks；after FRP wrapping，the energy accumulated by the increased load on the specimen cannot be released through the interface separation，resulting in a concentrated damage zone on the coal element. (2) As the interface angle in-creased，the interface crack changed from tensile failure to shear failure. After FRP wrapping，the development of interfacial cracks was significantly reduced，and the brittle characteristics of the specimens were reduced. (3) The strain zone of the specimens expanded along the loading or interface direction. FRP wrapping increased the tensile and shear strength of the interface. The stability of the interface increased. (4) FRP wrapping increased the AE counts and reduced the damage degree of the specimens when the specimens were damaged. (5) The number of AF-RA data points for the specimens increased after FRP wrapping. It indicates that the specimens were able to experience more crack generation and expansion before instability. This study is expected to provide theoretical guidance for the prevention of splitting instability in pillar-side backfilling.
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