Determination of the friction angle of soils in triaxial-compression apparatus and shear devices

Interpretation of the data of soil shear tests

“…The same such value of the angle of internal friction is obtained also as a result of testing the investigated sand of various densities and with various loading trajectories in stabilometers and apparatuses with independently adjustable principal stresses, but in processing the data on the basis of the assumption that the orientation of the shear planes is determined bv the kinematic conditions of interaction between soil particles [3,4,7]. The same such value of the angle of internal friction is obtained also as a result of testing the investigated sand of various densities and with various loading trajectories in stabilometers and apparatuses with independently adjustable principal stresses, but in processing the data on the basis of the assumption that the orientation of the shear planes is determined bv the kinematic conditions of interaction between soil particles [3,4,7].…”

“…On the basis of the results of investigating the limit equilibrium of cohesionless and cohesive soils under conditions of three-dimensional stress state, another viewpoint is examined in [3,4,8], namely: the orientation of the failure surface, which is determined by kinematic conditions of the interaction of soil particles, depends on density and the trajectory of loading or deformation; the state of limit (plastic) equilibrium is described by the Coulomb dry-friction law for a constant value of the angle of internal friction, which depends only on the composition of the soil. The angle of internal friction is the only physical parameter determining the state of the soil at limit equilibrium.…”

“…The loadtrajectories are shown in Fig. These same data processed under the assumption of a variable orientation of the failure sur- faces with nornal v by the method proposed in [3,4,8] substantiate the relation with a unique correspondence between the shear r~ and normal o~ stresses in a state of limit equilibrium at a value of the Coulomb angle of internal friction ~c=28,~. In the given representation of the experimental data a constant shear plane is examined -the plane with the maximum value of the shear stress.…”

Strength and deformability of soils in a complex stress state

“…Experiments conducted by Kryzhanovskii et al [2] have demonstrated that the strength of a soil differs for different forms of stressed state, including generalized compression and tension. It is established experimentally that the influence exerted by the form of stress state on the strength of a soil will depend on the density of its composition and the load path.…”

“…is the generalization most acceptable from the physical standpoint, where (2) are the normal and tangential stresses, respectively, on the spatial platform of limiting equilibrium, ϕ is the effective angle of internal friction, and I 1 = σ 1 + σ 2 + σ 3 , I 2 = σ 1 σ 2 + σ 1 σ 3 + σ 2 σ 3 , and I 3 = σ 1 σ 2 σ 3 are the invariants of the stress tensor. The normal v to the limiting-equilibrium platform is defined by the direction cosines where σ i (i = 1, 2, 3) are the principal stresses (σ i > 0 corresponds to compression, and the numeration of the stresses is adopted proceeding from the condition σ 1 σ 2 σ 3 ).…”