Prefabricated mould for test specimen of irregular rock mass joint-plane shear test

The invention discloses a prefabricated mould for a test specimen of an irregular rock mass joint-plane shear test. The mould comprises a bottom board, two side wall boards and two side baffle boards, wherein the two side wall boards are respectively fixed at the opposite end parts of the bottom board, and two parallel grooves are formed in the inner wall of each side wall board; each side baffle board is fixed on the bottom board by being embedded into the two grooves in the corresponding positions on the two side wall boards, and each side baffle board is perpendicular to each side wall board; through holes are formed between the grooves in each side wall board and the edges of the grooves, a bolt is connected between the two through holes in the corresponding positions on the two side wall boards and extends out of the side wall boards; the two end parts of each bolt are fixed through nuts; observation holes are formed in the side wall boards and positioned between the two side baffle boards. The mould solves the problem that irregular cylindrical core obtained by drilling cannot be subjected to the shear test on a conventional shear tester, underground rock fractures can be more objectively and accurately analyzed and researched, and key analysis parameters are provided for safety stability evaluation for underground engineering.