Abstract: The planned construction depth of the new main well in Xincheng Gold Mine is 1 527 m. In order to explore the mechanical characteristics of tensile fracture of porphyry-like coarse-grained granite about 1 300 m in the main well， the granite samples from the prospecting borehole are collected. The loading process of split-loaded porphyritic granite is monitored in real time by means of strain detection device and acoustic emission detection equipment. The experimental results are as follows: （1） the transverse strain deformation of granite samples is divided into three stages， and the strain change process approaching to fracture shows the characteristics of unstable motion. （2） with the advance of the loading process， the overall activity of the acoustic emission counting rate increases gradually， and the change of the counting rate shows the characteristics of fluctuation with the time process， and gradually changes from sparse to dense. （3） based on the theory of motion stability and the analysis of vibration energy， it is concluded that the abnormal high value of energy carried by each acoustic emission signal on average can be used as one of the precursors of granite splitting failure.

Key words: Porphyritic granite, Brazilian splitting, Crack propagation, AE