In order to guide the production of block caving method with high horizontal in situ stress

the stress evolution law of the extraction level excavations during the process of undercutting with high horizontal in situ stress was studied

and the occurrence mechanism of specific characteristics of ground pressure disaster in the extraction level excavations was revealed. According to the actual engineering and physical parameters of the mine

a numerical simulation model was established by using finite difference software FLAC3D

and Mohr-Coulomb failure criterion was adopted in calculation. In the simulation process

the extraction level excavations were excavated firstly according to the backward undercutting method. The process of the undercutting was divided into three steps

and the stress states of extraction level excavations after each step were monitored and analyzed respectively

which were compared with the actual situation of ground pressure disaster on site. The results are consistent with the evolution law of ground pressure disaster on site

showing that with the development of undercut blasting

compressive stress concentration gradually occurred in the extraction level excavations in the vicinity of the undercut front. Ground pressure disasters occurred when the compressive stress increased beyond the shear failure condition of rock mass. Tensile stress concentration appeared in the extraction level excavations below the undercut layer

and ground pressure disasters occurred again when the tensile stress increased beyond the tensile failure condition of rock mass. Under high horizontal in situ stress

the extraction level excavations of block caving method presented the stress law of "compressive stress concentration followed by tensile stress concentration". With the increase of undercut area

the extent of compressive stress and tensile stress concentration became increasingly obvious

thus ground pressure disasters occurred repeatedly in the extraction level excavations in actual production.