This invention discloses a method for determining the
rock failure surface during drilling, comprising the following steps: 1) simulating and determining the
drilling force model, and determining the relationship between the components in the model; 2) calculating the maximum
shear stress at which the
rock structure undergoes plastic failure; 3) determining the shape of the failure surface and the maximum
shear stress τ in the
shear zone determined in step 2) according to the maximum
shear stress criterion. max This is related to predicting the failure surface; 4) Based on the maximum shear stress criterion, the
iterative method is used to solve the force acting on the
cutting surface, and the function of the failure surface is determined by inputting the basic drilling parameters, quantitatively presenting the failure surface morphology. The method of this invention introduces the Michel solution of elastoplastic
mechanics to solve the stress state of the rock
shear zone during drilling, and derives a specific response function of rock properties to drilling parameters based on the stress characteristics of the
drill bit; referring to the maximum shear stress criterion, the shear stress of the unit body is compared with the
shear strength of the rock to determine whether the rock is broken.