AE CHARACTERISTICS OF GNEISS FRACTURE PROCESS UNDER UNIAXIAL COMPRESSION

This paper examines a typical gneiss forming the foundation Xiaowan Hydropower Station.Grinding test is ued to analyze the formation environment and mineral composition of the biotite granite gneiss.The results confirm the relationship of the rock strength with its mineral content and mineral strength.Furthermore,acoustic emission is carried out during the uniaxial compression tests of the biotite granite gneiss samples.The acoustic emission process is examined during the biotite granite gneiss instability and rupture.the AE results are used to analyze the crack propagation with time,stress and strain.The results are meaningful for the analysis of rock fracture instability mechanism.They reveal that the gneiss is hard-very hard rock.Acoustic emission activities substantially follow the same patterns.There is a clear point of AE enhancement.Acoustic emission ring count rate of rock rock failure process is suitable for predicting for all stages of the breakdown of rocks.The relations of gneiss stress-strain are in the form of polynomials of second orders.The relations of strain-the cumulative number of AE are in the forms of polynomials of third orders.It will help us to better understand the failure mechanism and the precursor of rock failure criterion.