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№1/2016

 

Magazine «Geotechnics» , 1/2016

 

Calculation of settlements and tilts of engineering structures taking into account uncertainty of foundation soil properties

Barvashov V.A., Boldyrev G.G., Utkin M.M. ...4

Engineering-geological survey data are highly uncertain due to small volumes of tests, data distortion by test tools, statistic scatter, interpretation errors, subjectivity of data interpretation in reports, etc. Therefore calculation results of settlements and tilts of engineering structures are ambiguous, i.e. their scatter is wide and depends on the sensitivity of an engineering structure to the survey data uncertainty. The paper proposes a calculation method of settlements and tilts using the MathCad computer-aided design system. The authors present a calculation example showing that tilts scatter can be inadmissible at relatively narrow average settlement scatter. The article is published as a basis for discussion.

KEY WORDS Calculation of settlements of engineering structures; calculation of tilts of engineering structures; MathCAD computer-aided design system; uncertainty of engineeringgeological survey data; uncertainty of foundation soil properties; scatter of data.

Urban seismology and features of engineering-geological surveys for construction in Kaliningrad

Anosov G.I., Dementiev Yu.V., Il’in A.G. ...22

The conditions of using the concept of urban seismology for the Kaliningrad city are considered. It is shown that impacts of anthropogenic microseismic vibrations which can significantly distort design expectations for timeframes and quality of operation of buildings and structures come out on top. The authors offer to create measuring networks for continuous detailed monitoring of microseismic noise in cities with intensive automobile traffic and intra-urban railways, especially in districts with high building density or with hazardous industries.

KEY WORDS Seismic vibrations; zoning; urban seismology; measurement networks; dynamic parameters of buildings; traffic; stability limits; vibration safety of engineering structures.

On displacements of pile foundation elements at digging of pits

Vershinin V.P., Gaydo A.N., Sergeev Yu.O. ...32

Questions of quality assessment of pile foundations are considered. Regularities of horizontal displacements of piles caused by the lateral pressure of soils are explored. Some concrete examples from the practice are given. Technological schemes are presented. The main causes of such displacements are discussed. Methodological approaches to modeling of the stress-strain state of a soil massif in specialized software packages such as PLAXIS 3D for assessment of displacements of piles caused by the lateral pressure of soils are considered. Measures for exclusion of such displacements are proposed.

KEY WORDS Pile foundation; foundation pit; geotechnical modeling; horizontal displacements of piles; lateral pressure of soil.

Force interaction of a detached foundation with the ground base at low-cycle loading

Dyakov A.I. ...40

Issues of work of detached foundations in the limit and out-oflimit state at low-cycle loading are considered on the basis of results of experimental and theoretical studies. Influence of repeated loading on the ultimate bearing capacity of foundations is established. Stages of changing the stress-strain state of a foundation and destructing it due to punching are revealed. Transformation of the diagram of normal contact stress distribution under the bottom of a detached foundation at low-cycle loading is investigated. A computational model is developed for determination of ordinates of the normal contact stress distribution diagram and for capacity calculation of a foundation taking into account the previous load history.

KEY WORDS Pier foundation; low-cycle loading; ultimate bearing capacity (ultimate resistance); normal contact stresses; out-of-limit state; previous load history.

Experimental research of work of a slab foundation with a damping layer on the ground base

Kiselev N.Yu. ...51

Decrease of the cost and increase of the operation quality of a slab foundation due to rational loading of the ground base are numerically substantiated. It is shown that the bending moments in the foundation slab depend on nonuniformity of settlements of the ground base. It is proposed to equalize the deformability of the ground base at the expense of creating a damping layer under the slab bottom in areas with lower settlements. The concept of a slab foundation with a damping layer on the ground base (SFDL) is considered. A field experiment for study of interaction of a SFDL with its clay ground base is described. Experimental research results of the work of a SFDL are presented. Results of implementation of a SFDL in the design of a 22-storeyed residential building are considered. Technoeconomic comparison of a SFDL with foundations of standard constructions is presented.

KEY WORDS Shallow foundation; slab foundation; numerical simulation; specified loading; field experiment.

The experience of restoring the emergency building of the Vvedenskiy

Cathedral in Cheboksary Sokolov N.S., Sokolov S.N., Sokolov A.N. ...60

The article describes the experience of restoration of such historical and cultural monument of federal significance in the Cheboksary city as the Vvedenskiy Cathedral. As a result of construction of the two-storey building of the church hierarch’s residence of the Cheboksary Archdiocese and Chuvash Eparchy in the geotechnical influence zone, the cathedral got deformations that were dangerous for its safe operation. The cathedral building was managed to save from destruction owing to opportunely emergency response measures.

KEY WORDS Historical and cultural monument; Cheboksary city; Vvedenskiy Cathedral; emergency response measures; strain crack; cantledge; prestressed braces; root piles.

Peculiarities of determining parameters of contemporary soil models by laboratory tests

Ter-Martirosyan A.Z., Mirnyy A.Yu., Sobolev E.S. ...66

Continuously improved software packages using numerical simulation methods and mathematical models of soils developed in them allow to take into account such specific properties and effects of the soil medium as deformation nonlinearity, creep, hardening, softening, filtration processes. These models require laboratory test determination of many parameters that are not reflected in the current regulatory documents. At the same time the technical capabilities of the widespread test equipment are not enough for determining parameters that require high stresses and high precision of strain measurement. This paper considers the experience of determining such parameters in the laboratory of the “Geotechnics” research and education сenter of the “Moscow State University of Civil Engineering” national research university, technical requirements for the equipment, features of its use, recommendations on application of the research results in practice.

KEY WORDS Dynamic tests; triaxial tests; nonlinear deformations; creep; hardening; softening; soil model; soil parameters; small deformations; mathematical modeling.

 

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