Angle and size adjustable large-scale dynamic monitoring similar simulated experiment system for 3D mining-induced fractures

In order to enrich similar simulated experiment study methods on spatiotemporal evolution characteristics of mining-induced fracturing and fractures(MF)in mining and geotechnical engineering,this paper presents a large-scale laboratory angle and size adjustable dynamic monitoring SSE system for 3D-MF(3D-LADMF)which is composed of four subsystems,i.e.,the active electro-hydraulic servo hydraulic loading-counterforce subsystem;angle and geometry size adjustable sample chambers;the measurement-control subsystem composed of MaxTest-Load software with 13 control channels,data acquisition sub-subsystem with 128 channels,and the multilevel dynamic monitoring sub-subsystem of 3D-MF;Large area caving machines and tools under tri-axial loading as well as other accessory devices.The features of the 3D-LADMF focus on locating loading-counterforce subsystem in ferroconcrete counterforce pond below the floor,which not only reduced the height of device to easily climbing,but also improved stability.Test specimen can be always under tri-axial loading in the whole process of the experiment,and it's fairly convenient to realize diversified caving and observation with opening or closing the 8 mid-front openings across counterforce wall to sample chamber and equipped caving machines&tools.Through a pair of synchronous telescoping large-tonnage hydraulic jacks and screw hole arrays flexibly setting,large inclination angle ore&rock can be easily well simulated with 0～45° steplessly adjustable angle of the sample chambers and the geometry size also can be adjusted within 3 m×3 m×3 m,2 m×2 m×2 m,1 m×1 m×1 m,et al,thus the 3D-LADMF can meet with experiment requirements under different working conditions and increase equipment usage accordingly.Multichannel data acquisition system is compatible with majority of stress and displacement sensors and data real-time capturing,transmitting and displaying with equipped MaxTest-Load measure-control software which possesses both stress and displacement individual control and self-programming function,and most importantly the holding time can be set arbitrarily to realize tri-axial uniformly or non-uniformly distributed loading by freely group control and full-closed loop control with high precision.Test results shown that 3D-LADMF accords with design accuracy,and what matters is how to use a set of loading-counterforce system and measurement-control system to realize both angle and geometry size adjustable and diversified 3D caving&observation under tri-axial loading in the whole process of the similar simulated experiment.The presented 3D-LADMF creates a favorable test condition for the research of non-linear dynamics problems in geotechnical engineering and especially the spatiotemporal evolution characteristics research of deep coal and rock 3D-MF,which is of wide utilizable prospect in large-scale dynamic monitoring similar simulated experiment in the future.