BACKGROUND OF MODERN TECHNIQUES FOR LABORATORY DETERMINATION OF THE ELASTICITY MODULUS OF COHESIVE SOILS AND THEIR DESIGN CHARACTERISTICS IN THE ROAD STRUCTURE (Part 2)

Abstract

According to the results of laboratory stamping tests, samples (d = 150mm; H=180mm) of bulk with soil compaction having a water saturation factor Sr≥0,85 in the range of values of fluidity index – 0,5≤lℓ≤0,25 , it is concluded that it is possible to determine practically every sample, their modulus of deformability (Епр; Ед), the calculated critical resistance – Ro of soil and its maximum relative deformation λmax. The loading of the samples is carried out by a step load with a proportional (1.3 times) increased pressure, such as at each stage. During the test, the sample is not unloaded but is subject to conditional destruction, that is, a disproportionate increase in the deposits of the die. The duration of each load is three minutes. The graphs of parabolic functions of the type λ=aσb are plotted in logarithmic coordinates in the form of two segments straight on both sides of the fracture. The parameter of the degree of parabola “b” serves for preliminary estimation of the index of deformability: for the modulus of elasticity – b≈1,0 ± 0,2; for the modulus of deformation – b≈2,0 ± 0,5; for the yield modulus – b≥3.0. The work gives a comparison with similar indicators of deformability of other building and structural materials. The elastic modulus (Епр) has only a soil that meets the conditions of the standard seal ρdmax>ρdωρ і ω_o<ωρ; the modulus of deformation (Ед) has a soil when 0<lℓ<0,5, and the modulus of fluidity (Ет) has only a soil lℓ≥0,5. Natural structured soils are characterized by a modulus of structural strength (Est) in the range 0<lℓ< 0, which is determined by compression tests. In order to reduce soil consumption and increase productivity, it is proposed to consider the task of determining soil deformability indices for the calculation of road clothing as a contact and therefore reduce the height of soil samples from 180 mm to 40 mm Keywords: soil, soil engineering structure, compacted soil, design condition, elastic modulus, critical design resistance, maximum relative deformation.