Test fixture and method for three-point bending and four-point bending of rock

The invention discloses a test fixture and a method for three-point bending and four-point bending of rock. The fixture comprises a base, an auxiliary carrier plate, an upper pressing head, a lower pressing head and a fixed pressing head. Supporting rods and fixing pieces are arranged at the two ends of the base, the auxiliary carrier plate can move on the supporting rods and is fastened through the fixing pieces, grooves are formed in the upper surfaces of the two ends of the base, base rails are arranged on the two sides of the base between the grooves, and the two lower pressing heads are movably connected in the base rails. Fixed pressing heads are symmetrically installed in the middle of the upper surface and the middle of the lower surface of the auxiliary carrier plate, a loading pressing head is installed above the fixed pressing heads on the upper surface of the auxiliary carrier plate, auxiliary carrier plate rails are arranged on the two sides of the auxiliary carrier plate,and two upper pressing h