Acoustic emission signal sources and critical failure precursors of weakly consolidated sandstone with different grain sizes

The characteristic parameter data of acoustic emission signals of weakly cemented sandstones and their correlation characteristics were studied,which can be used to distinguish the acoustic emission signal sources of different granularity weakly cemented sandstones during the failure process.It is also the basis for establishing critical failure criteria for weakly cemented sandstones with different grain sizes.Acoustic emission (AE) tests were carried out on the whole process of damaging sandstones with different particle sizes under uniaxial compression.The evolution of stress and AE characteristic parameters during the whole process of rock specimen failure was obtained.The distribution relationship between the AE ringing count and the parameters of absolute energy,amplitude,and duration is established to identify the characteristics of acoustic emission signal sources of weakly cemented sandstone with different grain sizes.At the same time,based on the analysis of the evolution characteristics of AE peak frequency,a method for identifying the precursor information of critical failure of weakly cemented sandstone was given.The results show that with the decrease of the particle size of the weakly cemented sandstone,the brittle failure of the rock sample is more obvious,the peak of the AE ringing count in-creases by an order of magnitude,the energy accumulation effect is more obvious,the self-accumulation ability of the rock sample is stronger,and a higher AE amplitude and a longer AE duration are produced.The weakly ce-mented fine-grained sandstone first appears in the lower frequency band (10-20 kHz) in the initial elastic stage,the weakly cemented coarse-grained sandstone appears higher frequency (275-285 kHz) in the AE peak frequency during the plastic deformation stage,and the AE peak frequency composed of two main frequency bands has evolved into five frequency bands.The weakly cemented medium sandstone has the largest cumulative count of the two main frequency bands (40-50,145-155 kHz) before reaching the stress peak.The higher frequency,lower frequency and main frequency cumulative count value can be a different identification basis for the acoustic emission signal source of particle size weakly cemented sandstone.When the rock sample enters the plastic deformation stage,the AE peak frequency appears to evolve from the initial two main frequencies to four or five frequency bands,and the frequency band increase phenomenon can be used as the precursor information for the weak cemented sandstone destruction.