"Вестник МГСУ"

Interaction between long piles and the adjacent soil has a spatial and temporal nature. This phenomenon is based on a set of non-linear and rheological properties of soils. Distribution of lateral forces between the surface and the pile toe is heavily dependent on the above properties. The process of formation of the stress-strain state around the pile can demonstrate decaying, constant or progressive velocity depending on the rheological processes in the soil that may be accompanied by hardening and softening processes at one and the same time. These processes may be caused by destruction and restoration of ties between clay soil particles, soil compaction and de-compaction. Predominance of the process of hardening leads to damping, while predominance of the process of softening causes progressive destruction. Description of this multi-component process depends on the rheological model of the soil. This research is based on the modified rheological model originally designed by Maxwell. The authors consider solutions to the problem of quantification of the stressstrain state of soil around the pile and their interaction. This research makes it possible to project motion patterns of long piles over the time and evaluate the limit of their long-term bearing capacity.

The article covers the problem of parameters that underlie the choice of mechanical properties of the clay stone used as the foundation material in Perm. The object of this study is the clay stone of the early Permtric modulus, effective cohesion intercept and angle of internal friction constitute tian age. Mechanical properties, including the deformation modulus, oedomehe subjects of the study. The authors enumerate the following tasks:1) description of geological conditions of the two sites of experiments in Perm,2) development of the methodology of identification of strength and deformation properties of the clay stone in the laboratory (oedometry testing and shear box testing of water saturated and water free samples) and on site (cone penetration tests, pressuremeter tests) according to the Russian technical regulations,3) experiments aimed at identification of mechanical properties of the clay stone,4) analysis and comparison of mechanical properties of the clay stone using various methods,5) provision of conclusions and recommendations concerning mechanical properties of upper layers of the clay stone in Perm.A lot of attention is paid to the analysis of results of cone penetration tests, pressuremeter and laboratory tests. The study has revealed a significant effect of test methods on the resulting values of strength and deformation properties of the local clay stone.

The authors consider particular aspects of influence of the thermal behaviour of soils of the active zone of bases of structures on the moisture and heat transfer inside the soil, their condition and deformation behaviour in the urban environment. It is noteworthy that any changes of the temperature gradient of soils caused by the moisture and heat transfer alter both the value of filtration ratios of soils having various compositions and their stress-strained state.The authors analyze the process of construction of a specific high-rise building in Moscow to prove that availability of systems of utilities emitting heat in Moscow soils at the depth of 3 — 10 meters below the ground level may increase the soil temperature up to 30 degrees C and even higher, whereas demounting of utility networks will cause an abrupt change in the thermal behaviour of the soil. Moisture redistribution causes heated and dehydrated soils to absorb moisture and to change their condition and principal physical mechanical properties.Having completed a series of field tests, the authors have identified that 1C reduction in the clay soil temperature reduces its modulus of deformation by 0.7…..1.0MPa. It is noteworthy that no projections of alterations in the principal physical and mechanical properties of base soils in the urban environment are possible absent of thermometrical tests accompanying geological engineering surveys. Findings of experimental and field research projects and their theoretical justification have proven that research into filtration properties of soils in the top zone of bases of buildings and structures and engineering networks in the environment of urban ecosystems require wide scale groundwater research to be performed within tight urban territories.

Soil vibration represents a problem endangering buildings and structures. Waves propagate through the soil and interact with buildings. Their interaction may cause damage to nearby structures. Horizontal Rayleigh waves or any other waves generated by dynamic loads are considered in this paper. The soil medium is assumed to be linear, elastic, homogeneous and isotropic. The energy associated with any surface waves can be absorbed and damped by the barriers due to geometric and material damping. Application of wave barriers as a method of isolation of structures and foundations from vibrations transmitted in the soil enjoys moderate success. In this research, various open and in-filled trenches used as wave barriers are studied. For this purpose, an extensive parametric analysis has been completed using FLAC-2D software. The findings have proven the efficiency of wave barriers if used in the presence of the structure and applied to suppress the effect of impulse loading on the soil surface. The findings demonstrate that the proposed system composed of the in-filled trench and the structure performs well, as it efficiently reduces the energy of surface waves, although the findings have some exceptions. The discrepancy between the findings of the authors and other researchers may be explained by a different type of load and the presence of a structure.

Wave barriers are intended to mitigate vibration transmission in the soil. They include open and infilled trenches, sheet piles, etc. In this study, a two-dimensional finite difference element analysis was performed using FLAC-2D software as a research into the efficiency of open and infilled barriers exposed to dynamic loading with or without the presence of structures. In this contribution, two constitutive models are considered to study the soil response in the elastic and elastoplastic range with account for yield, failure and potential functions of soil plasticity. The results were assessed with account for reduced soil particle displacements on the ground surface exposed to impulse loading.The numerical analysis has proven that the results obtained by assigning elastic properties to the soil material fail to comply with the results obtained by analyzing the model having non-linear properties of soils. The presence of a structure produces a significantly larger effect onto the efficiency of barriers by reducing the surface wave energy.

The authors formulate and solve the problem of consolidation and creep of saturated clay subfoundations exposed to localized loads (the two-dimensional problem formulation). The findings have proven that, if the two-dimensional problem is considered, any excessive pore pressure is concentrated immediately under the area exposed to the localized loading, and it penetrates into the depth equal to 1/2 of the strength of the compressed width. Subfoundation subsidence is caused by both shear and 3D deformations of soil. Besides, the ratio of shear-to-3D deformations reaches 10. Therefore, the authors propose to represent the subfoundation subsidence as the sum of shear and 3D deformations.The differential equation of the filter consolidation, if considered as the 2D problem, is solved using the Mathcad software. The software is used to analyze the isolines of excessive pore pressure at any moment following the loading application. New depen- dence representing the ratio of the changing area of the diagram of the average effective tension to the area of the diagram of the average tension in the stabilized condition is proposed by the authors.In the final section of the article, the authors solve the problem of prognostication of the subsidence pattern for the water saturated subfoundation with account for the shear creep of the soil skeleton. The authors employ the visco-elastic Bingham model characterized by time-dependent viscosity ratios. The authors have proven that in this case the subsidence following the shear load will develop as of the moment of application of the external load pro rata the logarithm of time irrespectively of the process of filtration consolidation.

This study consists in numerical modeling of the nonlinear response of soil. The study is a research into the protective performance of both open and in-filled trenches and an examination of the influence produced by (1) the shape of trenches and (2) their position in relation to sources of vibration and structures on the isolation efficiency of barriers. Assessments were based on reduction in horizontal displacements of soil particles on the ground surface exposed to impulse loading. Also, results of numerical researches are analyzed and interpreted to provide recommendations for their implementation and guides for barrier designers. Three points of loading were analyzed and an attenuation curve of soil displacement was drawn; the curve follows the projected trends, as it decays in the horizontal direction on the ground surface. The structure produces substantial effect on the efficiency of open barriers in terms of the surface wave energy.

The paper is an overview of nationwide testing results demonstrated by pulse-discharge technology piles exposed to the vertical load under conditions of soft soils of Tunis coastal area. Bored cast-in=place piles are constructed through the employment of the pulse-discharge technology (PDT). In the construction norms of France, PDT piles are classified as bored piles, which are cast-in-place using a hollow stem auger; they are reinforced, and their diameter exceeds 25 centimeters. PDT piles are made through the application of high pressure to the surrounding soil in the course of concreting.Photos of testing facilities are provided in the paper. Graphs of cyclic and experi- mental load testing of piles, complying with the values of design loads for a 10-storey building under construction, are analyzed. The findings obtained by the authors have proven a considerable growth of the PDT pile bearing capacity in comparison with the analytical solutions obtained in accordance with Russian and French construction norms and regulations. It is pointed out that the results of pressuremeter testing can be reason- ably used in calculations as stated in the French norms. Negligible pile settlements and the high value of the bearing capacity of piles prove the expediency of employment of this technology in the course of construction of piles in the soft soils of the Tunis shoreline. It is concluded that further elaboration of the PDT pile calculation technique is required.

In the civil engineering practice, construction operations in loose and high compressibility soils require the application of compressed sand cushions. Recently, there has been a substantial decline in the use of compacted ground beddings in the practice of industrial and civil engineering. This can be partly explained by the weaknesses of the existing calculation methods that may often generate higher values of the size of compacted cushions (width and thickness) and, consequently, cause a substantial increase in their cost. It is noteworthy that the existing methods of calculation do not take account of strength and deformation characteristics of the cushion material in the course of identification of the cushion size and their operating bearing capacity.However, the studies implemented by different authors suggest the possibility of reducing the size of compacted soil cushions applied to loose and high compressibility soils. Therefore, the most effective are the pads reinforced by high-strength reinforcing elements (as geo-textile, geo-grids, etc.) The author elaborates on the possible methods of expanding the scope of compacted ground bedding in the practice of industrial and civil construction. The analysis of the findings of experimental and theoretical studies of compacted and reinforced soil bedding in loose soils is performed