Consideration of anisotropic properties of pebble soils in calculations of stability of slopes of soil dams

Abstract

Introduction. The results of experimental studies of the deformation and strength anisotropy of gravel-pebble soil laid in the body of soil dams are presented. In the course of stabilometric tests, different shear angles for the stone were obtained with different orientations of soil particles in the working chamber — horizontal and vertical. With an increase in the hydrostatic pressure in the working chamber to 0.8 MPa, a decrease in the shear angles of the stone by 8–12 degrees was obtained, depending on the direction of the soil layering. Materials and methods. During the processing of experiments, a function of the ratio of shear angles for a stone with different particle orientations, depending on the direction of the main stress at the shear site, was obtained as ψan = φ(min)/φ(max) = f(σ). Graphs of “hodographs of shear angles” are constructed to determine the calculated values of the strength characteristics of gravel-pebble soil, depending on the angle of inclination of the shear site to the axis of soil layering. The author’s calculation program ОТКОС_Ani (Delphi) has been compiled, taking into account the strength anisotropy of pebble soils for calculating the stability of slopes of soil dams and slopes. Results. For stone and stone-earth dams of different designs and heights, slope calculations were carried out and correction coefficients were obtained to account for strength anisotropy in slope stability calculations in the form of a function kan = Knan / Kn = f(H, γ, m). Conclusions. The functions of the kan change depending on the type, height and density of the gravel-pebble soil laying in the body of the dam are obtained. It is found that the “lowering” coefficient for taking into account the decrease in the strength properties of pebble soil with horizontal layering varies in the range from 1 to 0.9, which should be taken into account when choosing the design of soil dams with prisms of gravel-pebble soils.