The article discusses the problems associated with construction of pile foundations in structurally unstable soils, including permafrost soil, and ways to solve such problems on the example of slurried and auger cast (grout-injected) piles. The results of a laboratory experiment simulating the construction process of a slurried pile in sandy frozen soils are presented. The authors give the functional connections of changes in the temperature of the soil and cement-sand solution in time, determined the maximum radius of thawing and the total duration of the process of thawing and reverse freezing of the soil to the natural state as well as recommendations for the design of slurried piles taking into account the thermal interaction with permafrost soils. A laboratory study of the interaction of auger cast (grout-injected) piles with frozen soil is presented. The results of laboratory studies of the strength of cement mortars of different compositions tsolidified at negative temperature are presented. Recommendations on the choice of the solution composition for the device of auger cast (grout-injected) piles in frozen soil are given. The authors believe that the solution of the problems identified in the article associated with the use of improved types of pile foundations in complex geotechnical conditions will significantly improve the reliability of structures, reduce construction time and reduce economic costs.

The paper discusses the applicability of the interaction factors method for the prediction of settlement of pile foundations. Recommendations on the choice of the mechanical characteristics of the soil for the calculation are given. The results of the comparison of the settlement prediction by IFM and published results of tests of experimental foundations and the results of observations of the piled foundations of structures are presented. Good comparability of the settlement prediction with experimental data for calculations performed according to provided recommendations is shown.

The article presents the results of experimental studies of the dependence of the strength properties of frozen sands from the moisture and temperature. Strength for uniaxial compression of frozen fine sand was determined at temperatures of minus 1, 3, 5, 7 oC in the range of the moisture from 6 to 90%. The experimental results used to create the diagrams of the dependence of the frozen sand»s strengths from the moisture and temperature under uniaxial compression. Our experiments have shown that the greatest influence on the strength of frozen sand have total moisture (the ice content) and the density of dry sand (skeleton density). These parameters have the greatest impact on the strength of sand at its full water saturation. The strength of frozen sands also depends on the degree of filling of their pores with unfrozen water and ice. The experiments revealed important features of the dependence of the strength properties of frozen sands on their total moisture (the ice content). In particular, it was found that there is a narrow range of «optimal» moisture (the ice content) frozen fine and silty sands, within which their strength varies significantly, reaching its maximum value here. This effect must be taken into account in engineering research and design of engineering structures in the Extreme North of Russia.

The sections of the current regulatory documents on engineering&geological surveys and the design of bases and foundations related to the forecast of karst-suffusion danger are analyzed. A scheme for applying recommendations of SP 22133302016 is described and implemented to assess the possibility and extent of manifestations of karst hazard. It is shown that for the conditions of carbonate karst for many «potentially dangerous» areas, the use of these recommendations allows to reasonably convert them into the category of «non-hazardous».

The patented area of focus in the pile foundation construction - driven piles in punched (crushed) wells - is described. The most rational designs and promising technological schemes of their device are described, depending on the geotechnical and hydrogeological conditions of the development site. It has been established by analysis that the most developed technological schemes for the installation of pile foundations are most expedient to apply on bases composed of weak water-saturated clay, biogenic, loess subsidence, bulk, etc. specific soils, and the underlying bearing layer of compressible soil. To protect the foundations from the aggressive impact of soil-water-gas environment of natural or man-made origin on them, it is proposed to usescreens made of flexible synthetic elastic and other types of shells. It is proposed to arrange the foundations of hollow driven piles and blocks with a broad base according to a new technological scheme. The main technological operations in the considered soil conditions include punching a well to the underlying bearing soil layer; backfilling of hard and loose ground material into the punched hole; the formation of a broad base of a hard soil material; immersion (driving) in the the formation of a broad base of a hard soil material; immersion (driving) in the buried part of the well of precast concrete piles.

According to the results of the implementation of experimental work, the peculiarities of deformations of swelling-subsiding loams and clays of Quaternary sediments, with an increase in their humidity and an additional load on them from the weight of the planning embankment are considered.

Construction of shore protection and landslide control structures in the Republic of Crimea set a number of tasks related to the assessment of physical and mechanical properties of soils by field tests, assessment of slope stability with the presence of coarse grained soils.

The article presents new tables for the transfer from the results of compression tests to stamp tests. Tables are developed based on a comparison of stamp and tangential oedometer modulus. It is shown that the use of a tangent odometer module instead of a compression one is more correct. Another difference of the new tables is the possibility of accounting the initial consistency of the soil. The developed tables embedded into the new edition of the Set of Rules SP 22.13330.

The deformation modulus is the main soil deformation parameter. The paper includes some aspects associated with it: a terminology, a history, and methods of the determination including the oedometer test.

The paper includes FEM solutions for some geotechnical ULS designs among them the bearing capacity calculation, the slope stability assessment etc. It turns out that exact solutions are obtained if the associated plastic flow rule and a proper partition of the domain onto FE are used.

The article presents the results of numerical calculations of the distribution of forces in the piles at their work as part of different groups, different placement, quantity, and so forth. The changes in mutual interaction of piles and load distribution between the piles and the raft are given.

A two-dimensional contact problem about linear deformation of non-uniform soil mass under normal pressure of periodic system of smooth rigid punches was solved. Asymptotic solution was obtained provided the period is small as compared to linear nonhomogeneity scale. A simple finite formula for the additional displacement due to contact discreteness is derived. Systems of many structures in contact with soil (strip foundations, piles etc.), causing complications in numerical modelling, may be substituted by simple layer of Winkler springs with known stiffness.

The article considers information about polymer drilling mud, which will be alternative for widely use bentonite. Fluctuation limits assessment of basic mud physical specifications made by laboratory research. Simulation experiment shows trench stability made with polymer. Field experiment confirms these results. According to laboratory and field experiments, as far as interaction between polymer and ground water, concrete and pump reasonable range of application are defined.

Paper presents the results of laboratory studies of stress state effect on deformation characteristics in course of sand. The studies are based on the triaxle soil test results. It was found that deformation characteristics basically depend on the hydrostatic compression pressure and lesser - on the density. An empirical relationship, which allows to estimate an initial strain module E₀ from secant Е₅₀ was revealed. The obtained dependencies allow to take into account additional factors in course of settlement calculation by analytical methods.