Study On The Mechanical Properties And Fracture Propagation Of Gneiss In Jinchangyu Gold Mine

As shallow mine resources are gradually depleted,domestic mines are gradually shifting to deep mining.The research on the mechanical properties and failure laws of deep rocks is still in the initial stage,which brings great challenges to the safety of mine production.In order to explore the mechanical characteristics of deep rocks and the law of fissure rupture expansion,taking Jinchangyu Gold Mine-640 m deep gneiss as the research object,using acoustic emission technology and numerical simulation methods,experimental research on mechanical properties of deep rocks was carried out,and the main research was obtained.The results are as follows:1)The more intact rocks show the failure mode mainly dominated by tensile cleavage failure,while the deep fractured gneiss samples show the composite failure mode dominated by shear failure and supplemented by tensile failure.The uniaxial compressive strength of the more complete gneiss sample is about 110 MPa,the tensile strength is 10.66 MPa,the cohesive force is 6.24 MPa,and the internal friction angle is 43.2 °;while the deep fissured gneiss sample is unidirectional due to the existence of cracks.The axial compressive strength accounts for about 40.48 ? 72.74% of the complete sample,the tensile strength accounts for about 29.5 ? 63.5%,the cohesive force accounts for about 69.23%,and the internal friction angle decreases by about 6.4 °.2)From the three aspects of acoustic emission time domain,frequency domain and RA-AF density cloud image,three angles of quantity,scale and damage type,a method of qualitative macroscopic analysis of the evolution of fractures was constructed.The analysis shows that the method can comprehensively analyze the evolution of cracks,and it is concluded that the sudden increase of acoustic emission time-domain signal and the increase of frequency-domain feature density can be used as precursor characteristics of sample instability.The change law of acoustic emission ring count and energy rate can better reflect the micro-fracture rupture evolution law in the rock.3)The numerical simulation research on the evolution law of fracture rupture propagation shows that the length of the fracture is the main factor affecting the strength of the gneiss sample.When the dip angle is constant,the length of the fracture is negatively related to the cracking stress and peak strength of the gneiss.Fracture inclination is the main factor affecting the failure mode of gneiss.When the length is constant,the peak intensity of gneiss will increase gradually with the increase of fracture inclination 0 ? 90 °.Figure 50;Table7;Reference71...