Abstract: To investigate the initiation and propagation of hydraulic fracturing, a new type of hydraulic pressure supplying and controlling device and its operational approach are developed. The device consists of water pump, booster pump, air compressor, water guiding steel subplate and other components. This device is prone to combine with the pressure servo machine to complete the hydraulic fracturing experiment. It has the advantages of simple operation, high efficiency, low cost, and easy assembly, which makes the hydraulic fracturing experiment easier to be popularized in a wide range. The hydraulic fracturing test of rock-like specimens are carried out by using this test device. Hydraulic fracture propagation of specimens with pre-existing flaws under different confining pressures are studied and compared with that of specimens without pre-existing flaws. The experimental results show that when the horizontal stress difference is low, the pre-existing flaw tip exposes great influence on hydraulic fracture propagation, and the hydraulic fracture propagates towards it. With increasing the horizontal stress difference, the hydraulic fracture deflects towards the direction of the maximum horizontal stress. The experiment shows that the device developed in this research has high reliability and stability. This study has a promoting significance for the hydraulic fracturing test.

Key words: hydraulic fracturing, water pressure supply device, fracture propagation direction, pre-existing flaw, horizontal stress difference