بررسی عددی اثر لایه‌بندی غیر افقی خاک بر پاسخ لرزه‌ای تپه نیم ‌سینوسی

ارزیابی تشدید لرزه‌ای سایت و ارتباط آن با ساختارهای زمینی نقش مهمی در مهندسی زلزله و ارزیابی خطر دارد. امواج لرزه‌ای با تغییرات هندسی ناگهانی به دلیل اثرات توپوگرافی، به‌طور قابل توجهی، می‌تواند تشدید شود. با این‌ حال، سوالی که مطرح می‌شود این است که چگونه می‌توان تشدید ناشی از زلزله بر روی توپوگرافی را تخمین زد؟ در مقاله حاضر، از نرم‌افزار تفاضل محدود flac2d، برای تحلیل توپوگرافی تپه نیم‌سینوسی تحت رکورد زلزله لاندرز، استفاده شده است. نوآوری تحقیق حاضر، کاربرد لایه‌های خاک با زاویه‌ها و مصالح مختلف برای توپوگرافی می‌باشد که با هدف بررسی تاثیر زاویه لایه‌بندی غیر افقی خاک بر میزان تشدید حرکت لرزه‌ای تپه دنبال می‌شود. نتایج تحلیل به‌صورت بدون بعد نشان داده‌ شده و الگوهای نسبت تشدید نظیر جابه‌جایی افقی مقایسه می‌شود. با مقایسه نتایج حاصل شده، به این مهم دست یافته‌ شد که هر یک از پارامترهای زاویه لایه‌بندی مصالح توپوگرافی، ارتفاع، تعداد لایه‌های مصالح و نحوه قرارگیری مصالح لایه‌های موجود در توپوگرافی تپه از مولفه‌های موثر بر پاسخ لرزه‌ای ساختگاه هستند. با افزایش زاویه بین مصالح از 15 تا 45 درجه، میزان بزرگنمایی افزایش داشته و پس از آن، با بیشتر شدن زاویه از مقدار بزرگنمایی تا حدودی کاسته می‌شود.

numerical study of the effect of non-horizontal soil layering on seismic response of semi-sine hill

seismic resonance assessment of the site and its relationship with ground structures play an important role inearthquake engineering and risk assessment. seismic waves can be exacerbated by sudden geometric changes due totopographical effects, significantly. various parameters can be involved in the evaluation of topographicalcomplications. finally, the effect of all these factors should be summed up and considered in seismic designs. boorewas the first to use the finite difference method to examine the triangular hill under sh waves. in this paper,flac2d software is used to analyze the topography of semi-sine hill under landers earthquake record. flac2dsoftware is a finite difference program of itasca software that is used for continuous environments. each topographyis drawn to investigate the effect of layering of complication materials at angles of 15, 30, 45, 60 and 75 degreeswith a height of 20 m layered and to investigate the effect of height at heights of 10, 20 and 30 m and also withchanging the angle from 15 to 75 degrees. also, increasing the number of layers in topography with different anglesof 15 to 75 degrees and investigating the effect of placing layers with loose and dense materials is considered. mostof the time, numerical analysis of a new problem always begins with the simplest behavioral model. materialbehavior here is assumed like most previous studies that considered the behavioral model of materials as linearelastic model. an important factor that affects numerical results is the layering angle of the hills. therefore, semisinehills with different layering angles (15 to 75 degrees) exposed to the landers earthquake with alluvialfrequency related to each model are modeled with layers that have different properties in terms of density and shearwave velocity and poisson ratio. the ratio of maximum displacement of the desired point in the model withtopography to the maximum displacement of the desired point in the reference model here is expressed asamplification (ah). increasing the angle of the layers increases the topographic displacement amplification. thepresence of layering with impedance difference in the site causes seismic waves to be caught and increases theeffects of the site. at each layering angle, the height increase is equivalent to an increase in amplifications. in thisway, a model with a height of 30 m, in all angles, has the most displacement response. at all angles, as the numberof layers increases, the amplification of the topography is added. in the three-layer hills with increasing angle, awider surface area of the hill is composed of materials with the lowest shear wave speed, which along with thecomplexity of layering these hills, has increased their amplification. the impact of how to place loose and densenon-horizontal layers on seismic motion intensification is the last parameter studied in this paper. it can be said thatthere is a relationship between topographical and stratigraphy resonance, and in particular, stratigraphic effects havea greater impact on the characteristics of earth’s motion than topographical effects. by comparing the obtainedresults, it was found that each of the parameters of layering angle of topographic materials, height, and number oflayers and the positioning of loose and dense layers in semi-sine geometry are the components affecting the seismicresponse of the site.