Theory of pressure-tension failure and its applicability analysis

The traditional tension-shear failure criterion has proved unable to explain the objective reality of rock tension failure under pressure. It also overestimates the failure strength of rock tension failure under pressure. By combining the hypothesis of a nonuniform rigid body mode with the theory of maximum normal stress, the formation mechanism of rock tension cracks under pressure is described. A new pressure-tensile failure strength criterion capable of giving full description of rock failure strength and failure characteristics under complex stress is proposed. By summarizing related test results, the universality and accuracy of the pressure tension strength criterion are verified. A PT–PS model capable of identifying pressure–tensile failure zones and pressure–shear failure zones is established and compared with the traditional model. The results show that as the traditional model overestimates rock strength under P–T state, when λ≤1/3 or λ≥3, it underestimates the range of the roadway surrounding rock plastic zone. This underestimation will further increase with the increase or decrease of λ. The PT–PS model gives a more realistic picture of roadway surrounding rock failure. Our new model can provide meaningful reference for evaluating the stability and designing the supports of underground works.