Criteria of Mora-Coulomb with Three Parameters of Material

Abstract

A modified Mohr – Coulomb criterion is presented. This criterion, in addition to adhesion and the angle of internal friction, contains the third parameter of the material (d). Depending on the value of this parameter (d), the modified criterion can take the form of the original Mohr – Coulomb criterion (with d = 0.5) or the original Treska criterion (with d = 0). For all other values of the parameter (d), varying in the range of 0 <d <0.5, the tangential stresses by the modified criterion are larger than the Mohr – Coulomb criterion, but less than the Tresca criterion. The paper presents the methodology and results of determining this parameter (d) using experiments on the triaxial compression of soils. The technique contains recommendations for the appointment the value of the axial strain of the sample material when determining the value of the parameter d. The value of the ultimate deformation is advisable to take in the range from 8 to 12%. This range is due to the fact that with axial deformation of the sample of 8%, the formation of slip areas begins in it, and with axial deformation of the sample 12%, the slip area is completely formed. In this case, the parameter d varies in the range 0 <d <0.5, having a shear strength bigger than in the Tresca criterion, but less than in the original Mohr – Coulomb criterion. The tangential stresses according to the modified criterion, on the contrary, have a bigger value than according to the Mohr – Coulomb criterion, but the values of the tangential stresses are lower than in the Tresca criterion.