Abstract: Based on the failure control conditions of “intensity parameters-stress environment-weak planes of joints” in coal-rock mass, the failure characteristic of overlying strata in large mining height face was studied, the simulation of failure process was conducted in the laboratory, and the determination of support resistance was theoretically analyzed. The following conclusions can be made: The caving of layers with thin and low strength depends on the scope of abscission layer, the main roof is characterized by the deformation feature of the clamped beam, and the position of fracture line depends on the scope of shear dislocation fracture. Tensile stress shows a continuous distribution type in thin and low strength strata, whereas a non-isolating distribution type is presented in thick and high strength strata. Shear-closed interlaminar fracture develops prior to the face as an inverted trapezoidal form in large scale, whereas tension-open fracture develops inferior to the face as an upward trapezoidal form in small scale. After fracturing, the lower main roof can form single key block structure and the higher main roof can form static three-hinged arch, and the stability of lower main roof is the key of roof control. Determination of the range of immediate roof is put forward according to the condition of single key block structure in lower main roof, the computational formula of roof pressure is deduced based on the principle of conservation of energy, and the influential degree of immediate roof property on each parameter is thus determined: cohesion > plastic modulus> friction.

Key words: large mining height face, failure condition, main roof structure, immediate roof, support resistance