Том 55, № 2 (2018)

The paper presents the well-known "mixed" problem solution for subsoil settlement analysis, accounting for soil cracks under footing edges whose depth is determined by iterations instead of abstract "plastic zones."

In this paper, the causes and mechanisms of residual loads are described and discussed. Methods for measuring pile residual loads in the field are summarized and compared. Specifically, a driven pile and a bored pile were selected to show the effects of residual loads on skin frictions and toe resistances. The results indicate that the skin friction in the upper pile portion and the vertical compressive stiffness of the test piles are overestimated, while the toe resistance is underestimated, if the residual loads are ignored.

The shear displacement method was used to simulate the response of pile groups considering pile-cap-soil interaction in layered soil. The pile cap was modeled using the finite element method with 16-node degenerate elements and the pile-pile interaction was assumed to be in a linear elastic state. The effect of the reinforcement effect between plies on the response of pile groups was considered. The obtained calculation results were compared with values estimated in finite element and field tests, and the feasibility of the proposed model for the analysis of a pile group and piled raft foundation was verified.

We present the results of simulation of the long-term interaction of dense Sarmat clays with water and establish the principal regularities of changes in the parameters of structure, composition, and the properties of clays under the conditions of diffusion leaching. We select four types of clays with different mechanical properties and compositions in which, under the long-term action of water, we observe similar quantitative and qualitative changes in the parameters of strength and swelling of soils. The proposed classification is used for the prediction of the strength of clays under the conditions of watering.

Based on the results of full-scale experiments, specifics of the behavior of a single-pile foundation in the form of a pyramidal-prismatic composite pile subject to lateral load have been established. Both "rigid" and "flexible" behavioral schemes were considered. A lateral load analysis procedure for a single-pile foundation in the form of a pyramidal-prismatic composite pile is presented. The calculation accuracy was evaluated by comparing the calculated and experimental data.

The mechanism of the interaction of soil and an underground pipeline is studied in order to determine the load arising on the pipeline from the pressure due to the backfill soil and automobile traffic. A more accurate calculation is made of the coefficient accounting for the relief of the pipeline by the soil located in the recesses between the trench walls and the pipeline, and the deformation modulus of the backfill soil is evaluated. It is shown that the distribution of the compressive stresses arising in the soil as a result of the surface traffic is similar to that of a uniformly distributed load.

This paper presents the behaviors of embankments on clay deposits improved by prefabricated vertical drains (PVD) in the north-east coastal plain of Vietnam. The deposit consists of soft Holocene clay (approximately 20 m) and stiff Pleistocene clay (approximately 20 m) on a thick sand layer. PVDs with various spacing were fully installed into the soft clay. Settlement behaviors mostly show a reverse-S curve that consists of three phases: small recompression, rapid and large settlement, and delayed settlement. When the spacing is smaller than 1.0 m, the recompression behavior disappears because of soil disturbance during installation. A nearly elastic behavior is observed during construction; thus, the ratios of lateral displacement to settlement (0.02-0.13) and of the excess pore pressure to the applied pressure (0.1-0.7) are significantly small.

The construction of heat-insulated sand pads for the base of low-load foundations of buildings on permafrost is studied. A method is developed for calculating sand pads with heat-insulation and using a ventilated basement, ventilation pipeline systems, and thermostabilization of soils.

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