ASSESSMENT OF SEISMIC GROUND CONDITIONS OF THE CITY OF OLMALIQ

Аннотация

The article discusses the results of field research conducted on the territory of Olmaliq for engineering and seismological justification of the master plan for the development ofthe city. Geophysical and engineering-geological surveys were carried out to assess the influence of soil conditions on seismic intensity parameters. Calculated values of peak ground accelerations on a free surface were obtained using the STRATA program. Based on a generalization of field and laboratory engineering-geological data, sections and a map oftheengineering-geological zoningofthe cityof Olmaliq were compiled. Keywords: engineering-geological conditions, Strata program, KMPV, MASW, soil conditionsmodels, soil reactionspectrum. Аннотация. В статье рассматриваются результаты полевых исследований, проводимых на территории Алмалыка, для инженерно-сейсмологических обоснований генерального плана развития города. Геофизические и инженерно- геологические изыскание проводились для оценены влияния грунтовых условий на параметры сейсмической интенсивности. Получены расчетные значения пиковых ускорений на свободном поверхности с использованием программы «STRATA». На основании обобщения полевых и лабораторных инженерно-геологических данных составлены разрезы и карта инженерно-геологического районирования города Алмалыка. Ключевые слова: инженерно-геологические условие, программа Strata, КМПВ, MASW, модели грунтовых условий,спектрреакциигрунтов. Introduction. In the city of Olmaliq, within the framework of the Decree of the President of the Republic of Uzbekistan dated May 30, 2022 UP -144 "On measures to further improve the seismic safety system of the Republic of Uzbekistan" and the Resolution of thePresident of the Republic of Uzbekistan dated May 16, 2023 PP -158 "On additional measures to further improve the seismic safety system of the population and territory of the Republic of Uzbekistan", many seismic observations were carried out. For this purpose, engineering- geological and seismological surveys are carried out to determine the engineering-geological conditions of the city's territory. The territory of Olmaliq has some specific features. Loess soils, sandy loams, sandstones, pebbles are widespread, in which seismic waves propagate differently, have different speeds of passage, different frequencies, accelerations, etc. Therefore, it is very important to intensify scientific research in the field of the influence of soilconditions ontheseismicityof construction sites. 98,7:ROTCAFTCAPMI.SECNEICS LACIDEM,5202, yraurbeF,5emuloV gro.srehsilbupcimedaca.www The main concept defining the features of engineering and seismological surveys is the model of seismic ground conditions. This concept includes all local features of the geological environment that determine the specifics of seismic impacts, their amplitudes and spectral composition[1-7]. Research methodology. A method for modeling seismic soil conditions for assessing the seismicity of construction sites is proposed, in which real engineering-geological and geophysical indicators of soils are studied, and the influence of soil conditions on the parameters of seismic vibrations under real impacts of strong earthquakes is determined. [5;7-15]. To solve the problems of assessing the seismicity of theterritory, the STRATA program was used, taking into account engineering and geological conditions. Actual accelerograms of two earthquakes were taken, which by their mechanism (normal and reverse) and by the nature of the propagation of seismic waves correspond to the seismological conditions of the territory of theRepublicof Uzbekistan. Next, materials were collected characterizing the engineering-geological and seismic properties of soils (based on archival materials and the results of complex geophysical studies conducted using seismic exploration methods KMPV (Correlation method of refracted waves), MASW (Multichannel Analysis of Surface Waves), and the physical and mechanical properties of the soil layer for 30 meters were also studied), which are widespread in the territory of the city of Olmaliq. Calculations of the seismic intensity increment were made based on the totality of seismic soil rigidities, the position of the groundwater level and the resonant properties of thesoils. The algorithm of actions for solving problems related to the development of seismic soil modelsis divided into 3stages. (Fig. 1) Stage 1.Collectionand systematization ofmaterials. 2ndstage. Data analysis and processing ofmaterials usingvarious programs. Stage 3.Generalizationofresults. 98,7:ROTCAFTCAPMI.SECNEICS LACIDEM,5202, yraurbeF,5emuloV gro.srehsilbupcimedaca.www Fig.1 -Algorithm ofactions for developing seismicsoil models Analysis. A loose layer of loess and loess-like deposits is present over most of the study area. However, its thickness varies significantly. It ranges from 20 m and more within the high terraces and decreases to 0.5 m on the I and II floodplain terraces of the Ohangaron River[