Abstract: The Brazilian test was conducted on sandstones containing vertical and horizontal laminations after 25 ℃ to 1 000 ℃ treatment. Digital imaging correlation (DIC) was used to record the evolution of the horizontal strain field of high-temperature bedding sandstone during the splitting process. Meanwhile, microscopic structural damage characteristics of samples after different temperatures treatment were investigated using scanning electron microscopy (SEM). The results show that: (1) The strain concentration of the bedding sandstone before splitting can be divided into two types: the strain concentration at both ends of the disk (≤400 ℃) and the strain concentration at the center of the disk (>400 ℃). (2) With the increase of temperature, the tensile strength of vertical and horizontal bedding sandstone first increases and then decreases and reaches the maximum at 200 ℃. With the increase of temperature at 600~1 000 ℃, the effect of bedding on the tensile strength gradually decreases. Temperature becomes the main factor affecting the tensile strength after a threshold temperature of 800~1 000 ℃. (3) The microstructure damage analysis shows that the sandstone matrix is mainly characterized by increased cracks and extended length after the lower temperature treatment, while the crystal is still intact. Also, after this treatment, both the number and size of pores in the bedding plane increase and more damage in bedding occurs. However, when the temperature is higher, the damage of matrix and bedding is very similar, which is the main reason for the variations in strain and strength of the sample after heat treatment.

Key words: high temperature, bedding sandstone, Brazilian test, digital image correlation technology, scanning electron microscopy