Zaalishvili V.B.
Zaalishvili V.B.

Zaalishvili V.B.
д-р физ.-мат. наук, проф., (Центр геофизических исследований ВНЦ РАН и РСО-А, г. Владикавказ)


Publications

To the Question of usage of Fractional Values of Seismic Intensity and Ground Acceleration
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"The paper discusses the results of a comparison of calculation of seismic intensity based on the integer and fractional values of initial seismicity in detailed seismic zoning (DSZ) and seismic microzonation (SMZ), as well as design of corresponding seismic hazard maps in values of peak ground acceleration (PGA). It is shown that, despite the fact that SMZ maps were designed using different approaches (with their own features), results are generally the same. And as always — non formal.

Nonlinear Properties of Soils (Part II)
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The parameters that are closely related to the absorption and soil nonlinearity were identified based on the analysis of instrumental records of strong motions. The empirical formulas connecting the areas of normalized and real spectra with the parameters of seismic action (magnitude, acceleration, epicentral distance, duration and weighted average frequency of ground motion) were obtained using regression analysis. The differences of absorption mechanism in dispersed (soft) and rocky soils were defined. The models of ground strata behavior in the case of variable intensity of dynamic action on the basis of consideration of the real area of the spectrum and the average value of the frequency, characterized by a linear and nonlinear elastic-inelastic deformation of the soils are offered.

Nonlinear Properties of Soils (Part I)
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The various aspects of the nonlinear properties of soils that are clearly exerted under strong loadings are considered in the present work. Nonlinear properties being the most important indicator of soils, as a rule, are not sufficiently taken into account during seismic hazard assessment and are limited by so-called geometric nonlinearity that is well described by the corresponding equations.

Behavior of soil stratum under impact of artificial source is reliably described by the hysteresis damping model. By changing duration of exposure it is possible to observe the reaction of corresponding amounts of soil strata, what supposes the need to solve most problems of seismic microzonation (SMZ) experimentally. This, in particular, makes it necessary to carefully analyze and further compare records of real and artificial impacts. Such an approach by analyzing records of Racha earthquake (Georgia, 1991) made it possible to identify and justify the application as new indicators of ground movement – areas of normalized and real spectra of ground motion. Further analysis made it possible to introduce indices of actual absorption and nonlinearity that are also based on their relationships with the spectral characteristics of the ground motion. The corresponding empirical formulas obtained. Selection of the most appropriate indicators of nonlinearity for practical use involves focused investigations.

Investigation of Seismic Waves Excited by Artificial Sources
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In spite of breakthrough in the field of engineering seismology a lot in the features of generation and identification of S waves still remains little-known. Seismic waves excited by artificial sources are considered in the article. Explorations include field investigations realized by the author in previous decades. One of the major problems is still a reliable identification of S waves. Thereby the phase inverse phenomenon of S waves generated by horizontal source in different types of soils was considered. The examples of the main types of seismic waves generated by vertical source by polarizing analysis method are given in the article.

Soils watering degree influence on the values of body seismic wave propagation velocities was investigated. Further a probabilistic assessment of the values of seismic wave velocities in different soil types was carried out. Obtained by the author empirical relations for soils density dependence on S-wave velocities in these soils are given in the article.

Evaluation Features of Fresh Groundwater Reserves in Exploitation Conditions of Interdependent Well Fields
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It is known that the seismic properties of dispersive soils are significantly affected by watering. At the same time the problem connected with change of mentioned properties in conditions of active anthropogenic impact is still poorly understood and phenomenologically limited. Thus the phenomenon of «drying» is rare in urban areas, where «flooding» is widespread. It is difficult to take into account in the projections the soil behavior during strong earthquakes, and it is of great scientific and practical interest.

As a result of extraction of groundwater intakes group localized in the city of Beslan massive cone of depression is formed. Dynamic impacts on soil increased as a result of the construction and expansion of enterprises, increase of railway and highway traffic due to seismic ground motions that can cause secondary deformation of soils, representing a danger to the population and the national economy of the city.

Investigation results on evaluation of fresh groundwater reserves of exploited Beslan deposit in RNO-Alania are considered. In 2004-05 hydrogeological investigations were conducted in the deposit in order to assess groundwater reserves in the generated hydrodynamic conditions and develop rational scheme of deposit exploitation. As the result of this work  the scheme of deposit exploitation has been modified and  measures that can prevent negative environmental effects were developed.

The Use of Nonexplosive Sources of Large Power With Seismic Microzoning
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In the article is carried out the analysis of practical-scientific works on seismic microzoning (SMZ). In spite of a change in the level of seismic danger from the time of their conducting [Building Codes II-7-81, 1982, 2000], the urgency of results did not decrease. The special action features of powerful nonexplosive sources, we have examined in a number of works, were used with SMZ of territories of Rustavi (1982), Gori (1983), Tkibuli (1985), Tbilisi (1989), Kutaisi (1990), etc.

With SMZ of Rustavi and Gori territories were used the surface pulse gas-dynamic source SI-32; with SMZ of Tkibuli territory — seismic vibrator SV-10/100; with SMZ of Tbilisi (1989), Kutaisi (1990) territories and individual sections of Big Sochi (1991) — seismic vibrator SV-10/100. With SMZ of Tbilisi and Big Sochi is for the first time used the simplified method, which helps to compose the vibration spectra (quasi-spectra) of the fluctuations of soils. With SMZ of Kutaisi territory (1996) is for the first time made the attempt to consider the nonlinearity of the soils of territory with the use of a seismic vibrator. The obtained results became the basis of the development of the new SMZ methods, which later were used for the estimation of the seismic danger of the territories of the areas of acting and projected Novovoronezh APS (1997).

Calculated Method of Evaluating the Ground Seismic Conditions
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In the article the existing methods of the realization of seismic zoning with the aid of the calculated method are examined. Are given the well known and newly developed calculated methods of seismic zoning, which form calculated method.

The use in the calculations of the indices of nonlinear phenomena makes it possible to maximally bring the eventual results of seismic zoning closer to the real physical phenomena, which are observed with the strong earthquakes. So, it is completely confidently considered by the so-called. bimodularity of soils. The calculated method of seismic zoning already gives the possibility to completely present the results in the form of accelerations. Consequently, in addition to the traditionally used intensity increments, it is necessary to obtain the results of the basic instrument method of seismic zoning also in the form of the accelerations.

Account of Seismic Impacts in Geomechanical Stability of Underground Structures
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Existing methods of underground mining design are not including special parameters for account of possible seismic events that cause additional dynamic effects on the elements of rock mass. Traditionally it is assumed that stability of underground structures on seismic effects is sufficiently large compared with terrestrial objects. Nevertheless, seismic effects may contribute to the loss of reserves due to dilution, and works at depth are of high risk here and even a minor factor is important. Calculations of stressed state of mining system at dynamical impacts is performed and seismic coefficient for safety factor assurance is proposed.

Algorithm Development of Information System Designed for City Planning
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Currently, among the geo-information systems a special place is occupied by The Information Systems Designed for City Planning, organized in accordance with the requirements of the Town Planning Code.

In order to standardize such systems, we have developed a structural-functional model of The Information System Designed for City Planning. Based on this model an algorithm is offered. This allows to create information systems that meet all the specified requirements. Thus The Information Systems Designed for City Planning maintains compatibility with other software products built according to this model and corresponding algorithm, as well as a number of existing information systems.

Taking into account the difference in the support excitation for multi-supported structures
Issue: #6-2021
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Three characteristics are proposed to describe the excitation differences under supports for calculating multi-supported structures. These characteristics include the non-synchronicity indicator t0, the incoherence indicator r and the non-uniformly scaled indicator z. The first characteristic shows the time shift between the excitations, the second characteristic shows the difference in the excitation frequency composition, and the third one shows the difference in the action amplitudes. To estimate the nonsynchrony index, two approaches have been proposed – maximizing the correlation function and minimizing the norm of the excitation difference. The proposed parameters fully characterize the acceleration inhomogeneity field at the construction site. However, they affect the system response in different ways. Small deviations in the index of excitation amplitudes z weakly reduce the structure response. As for the excitation incoherence, this effect can bring the system closer or away from resonance.