Sand-bearing rock is a special rock formed in the high-level key layer before water inrush and sand burst disaster. Its strength and mechanical properties are different from ordinary rock

which determines the stability of the high-level key layer. It is found that the fractured rock and sandy rock with different fracture angles have different characteristic stresses

and with the increase of fracture angle

the initiation stress

damage stress and peak stress of fractured rock and sandy rock increase

and the bimodal stress first increases and then decreases. The characteristic stresses of sandy rock under the same fracture angle are less than those of fractured rock

indicating that the sand body has a weakening effect on the characteristic stress of rock. From the perspective of failure form

the fractured rock is easy to show wing tensile fracture

the sandy rock is easy to form tensile fracture under the condition of low fracture angle (30º) and shear fracture under the condition of high fracture angle (60º)

indicating that the sand body has shear effect on the rock after entering the rock fracture. At the same time

the mechanical model of sand filling is established

and it is pointed out that the reason why the strength of sandy rock is less than that of fractured rock is that the sand body reduces the friction coefficient of rock. Based on the cumulative acoustic emission ringing counts

the amount of rock damage is defined and the mechanism of sand-bearing rocks causing the disaster is analysed. The on-site sand-bursting disaster can be divided into four phases: 1) elastic deformation phase; 2) fracture expansion phase; 3) sand and energy storage phase; 4) sand-bursting energy release phase. Finally

PFC2D is used to verify the differences between fractured rocks and sandy rocks

and the energy evolution laws of different types of rocks are analyzed. The research results can be used as precursory information identification of water inrush and sand burst phenomenon in coal mine roof

and help to guide the safe production of water inrush and sand burst face.