Scientific Journal of KubSAU

The conception of mobile contact has been suggested for the clay particles and their microaggregates. The contact has been presented as the plane particle between microaggregates, which can turn over the point of fixing to one of them and interacts with both of them. There has been shown that contact particle describes elastic and plastic-viscous resistance to transference of adjacent microaggregates

The deformation model of sand soil that takes into account the formation of clusters of particles, and method of measuring its characteristics is suggested. The physical basis of the method is the effect of the stepwise increasing of the sand probe at the odometer pressure by the constant rate of loading and the continuous measuring of deformation. The analysis of settlement and its rate has been allowed to determine the microstructural characteristics of the two-order deformation model of sand. According to the proposed model, with compression of the probe in odometer compaction of the sand takes place due to local strains on the sliding surfaces. The sliding surfaces allocate clusters of sand, and the separated layers of clusters are registered by device in the form of steps of deformation. Layer formation of clusters is initiated by the rigid stamps through the largest mineral grains. Cluster layers create the asymmetric microstructure of the sand probe, its compaction is non uniform but also anisotropic. At the initial interval value of the pressure, the formation of primary clusters occurs, and once they cover the entire probe volume, the compaction of the sand is by crushing them on the secondary smaller cluster sizes. The change of mechanism of the compaction is manifested in the sharp decrease of the settlement rate. The compaction process continues while a larger increment of pressure at each step. The deformation model allows compute the pressure value at which the compaction of the sand reaches the theoretical limit

Hardening of clay soil manifests in the form of increase of the resistance of sample to shear deformation. The shear tests of normally compacted and overcompacted soils give values of peak strength at small strains and long-term strength at high. A shear test with constant strain rate of deformation (CRD) with continuous recording of resistance encounters uneven resistance change and the cyclical rate of change of resistance (RCR). The identification of cycles of the SIS allowed us to divide the deformation in each cycle for elastic and inelastic, corresponding to the ascending and descending branches of cycle. On an interval of the total resistance, the increases of the increment of inelastic strain are positive up to some critical value of the total deformation of the sample at which their sum reaches a maximum. This maximum is adopted as a measure of hardening. With further shearing of the sample, inelastic increments are negative, and their sum is monotonously decreases and reaches negative values for the total destruction of the sample. This value is taken as the softening. A symptom of total failure of the sample is the decline of absolute values of inelastic increments of resistance to zero. In general, the trend of the increments of inelastic and elastic increments of the resistance of the sample indicates the development of the destruction of the soil sample on the sliding surfaces and, in particular, yielding of the total surface. The sum of elastic increments of the resistance monotonically increases throughout the shear

The odometric compression of sand with constant rate of loading (CRL) or constant rate of deformation (CRD) and continuous registration of the corresponding reaction allows to identify the effect of stepwise changes of deformation (at the CRL) and the power reaction (at the CRD). Physical modeling of compression on the sandy model showed the same effect. The physical model was made of fine sand with marks, mimicking large inclusions. Compression of the soil at the CRD was uneven, stepwise, and the strain rate of the upper boundary of the sandy model changed cyclically. Maximum amplitudes of cycles passed through a maximum. Inside of the sand model, the uneven strain resulted in the mutual displacement of the adjacent parts located at the same depth. The growth of external pressure, the marks showed an increase or decrease in displacement and even move opposite to the direction of movement (settlement) the upper boundary of the model ‒ "floating" of marks. Marks, at different depths, got at the same time different movements, including mutually contradictory. The mark settlements sudden growth when the sufficiently large pressure. These increments in settlements remained until the end of loading decreasing with depth. They were a confirmation of the hypothesis about the total destruction of the soil sample at a pressure of "structural strength". The hypothesis of the "floating" reason based on the obvious assumption that the marks are moved together with the surrounding sand. The explanation of the effect of "floating" is supported by the fact that the value of "floating" the more, the greater the depth

The basis of foundation settlement modeling over the plate testing has been offered. The similarity criteria were formulated so as the formulas for settling incre-ments calculation versus to setting pressure increments on the base of foundation. New principle of admissible pressure on the base of foundation has been suggested

The method of determination of clay soil microstruc-ture characteristics over the results on consolidation testing with constant rate loading has been described. The characteristics of 12 different soils are presented.

The preconsolidation pressure of natural loamy soils was researched with the method of constant rate of loading (CRL) and the continuous measuring of de-formations at the apparatus AKP-6NM. The results of the rate of deformation analysis have been offered. The method of the preconsolidation pressure and the crumple pressure values has been suggested based on the rate of deformation analysis