Abstract: This paper presents the qualitative and quantitative testing results of expansion characteristics of rock samples by testing the relative content of montmorillonite and other clay minerals in the rock samples from Hemaquan Area by X-ray diffraction test and the existence of lamellar crystals and the development of rock fractures in the microscopic characteristics of rock samples. The results of X-ray diffraction test and the content of mineral composition combined with the results of electron microscope scanning test reasonably explain the phenomenon of disintegration, expansion and even argillization of the soft rock in Hemaquan area. In order to further quantify the expansion performance of rocks in Hemaquan area, through the free expansion rate test without load, the test shows that the free expansion rate of rock samples is basically 30% ～40%, and some are even as high as 103%. The results show that there is no correlation between the free expansion rate and the self-weight stress.

Key words: expansion characteristics, x-ray diffraction test, free expansion rate, electron microscope scanning test