The article presents the results of experimental studies of alternating torsion under a rigid loading regime, during which the features of the behavior of materials under such loading are revealed. The study of deformation diagrams in the sequence of load cycles and under loading with a stochastic sequence of intermediate unloadings of the sample is carried out. In this case, external force and deformation were measured, followed by recalculation into tangential stresses and the relative twist angle. It is established that the hysteresis loop of the first loading cycle differs considerably in shape from the subsequent cycles, but after three or four loads, the dimensions and shape of the loop in all cases stabilize. When loaded with intermediate discharges, small random loops do not go beyond the main (limiting) hysteresis loop, but are inside it, and the inner and outer branches are similar curves

Keywords: torsion, deformable in the elastoplastic region, rigid loading regime, pattern deformation pattern, loading cycle, energy absorbing element, hysteresis loop

This article presents the results of the experimental study of how the loading rate effects the strength characteristics of soft soils. As such characteristics, the shear strength of soil was used being equal to the magnitude of tangential stresses when the limiting state was reached. The magnitude of the shear strength is considerably dependent on the strain rate. The experimental determination of this dependence was performed using the method of dynamic penetration of an axisymmetric body into the soil. Along with that, a direct measurement of stresses acting tangential to the surface of the body during its penetration into the soil was effected. Experimental studies were carried out for the body being penetrated with the range of rates from 2 to 100 m/s. It has been found that within the range of rates from 2 to 10 m/s the magnitude of the shear strength of soil increases as the loading rate grows. Further, its magnitude starts decreasing and at the rate of over 95 m/s becomes negligible. This gives grounds to construe soft soils subjected to dynamic loading as a compressible liquid.

Keywords: limiting soil state, shear strength, soil strain diagram, strain rate, method of dynamic penetration, compressible liquid