بررسی اثر انحنای دیواره بر پاسخ لرزه‌ای شیروانی‌های سنگی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی معدن، دانشگاه صنعتی اصفهان،اصفهان، ایران

2 دانشکده مهندسی معدن، دانشگاه صنعتی اصفهان، اصفهان، ایران

3 داشنکده مهندسی عمران، دانشگاه صنعتی اصفهان، اصفهان، ایران

10.29252/anm.2021.15924.1480

چکیده

بررسی پایداری استاتیکی و لرزه‌ای شیروانی‌های سنگی و خاکی در پروژه‌های عمرانی و معدنی ازنقطه‌نظر فنی و اقتصادی و بر اساس ملاحظات ایمنی از اهمیت ویژه‌ای برخوردار است. تاکنون مطالعات زیادی در این بخش صورت گرفته که اغلب آن به‌صورت استاتیکی بوده و مطالعات لرزه­ای محدود نیز تنها بر روی پارامترهای منبع زلزله متمرکزشده‌اند و تأثیرات محلی شامل توپوگرافی و اختلاف سختی مواد کمتر مورد توجه قرار گرفته است. از طرفی انحنای شیروانی‌های سنگی ازجمله مواردی است که بسیار محدود و تنها برای تاج شیروانی در دو بعد بررسی شده است. هدف این پژوهش بررسی اثر انحنای دیواره شیروانی در شرایط بارگذاری دینامیکی است. به این منظور تأثیر انحنای دیواره شیروانی در سه بعد با نرم­افزار عددی FLAC3D مورد بررسی قرار گرفته است. در این مطالعه دو مدل پیت و پیت معکوس بیضی‌شکل با انحناهای بین 25 تا 250 متر به‌وسیله پارامترهای ژئومکانیکی معدن چغارت مدل‌سازی شده و تحت بار استاتیکی و بار لرزه‌ای متداول منطقه مورد تحلیل قرار گرفته است. نتایج حاصل تطابق خوبی با مطالعات استاتیکی و دینامیکی دیگر محققان دارد. نتایج به‌دست‌آمده نشان می­دهد جابه­جایی دینامیکی مدل­های مربوط به پیت معدنی مانند مدل استاتیکی آن­ها کم است، درحالی‌که در مدل­های مربوط به پیت معکوس جابه­جایی برخلاف مدل استاتیکی قابل‌ملاحظه می­باشد. همچنین تحلیل­ها نشان می­دهد که در هر دو مدل با افزایش شعاع انحنا در ترازهای یکسان، میزان جابه­جایی و شتاب سطحی نیز افزایش می­یابد. درنهایت فاکتور تقویت شتاب (AF)، در مدل­های مختلف مورد بررسی قرار گرفته است که مقدار آن بسته به شعاع انحنا در مدل­های پیت معکوس بیضوی بین 5/4 و 6 و پیت بیضوی بین 3/0 و 2/1 است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating the Effect of Wall Curvature on Seismic Response of Slopes

نویسندگان [English]

  • Sadegh Tahmasbi 1
  • Amin Azhari 2
  • Saeed Mahdavi 1
  • Hajar Share Isfahani 3
1 Department of Mining Engineering , Isfahan University of Technology, , Isfahan ,Iran
2 Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran
3 Department of Civil Engineering, Isfahan University of Technology, Isfahan, Iran
چکیده [English]

Summary
The effect of slope wall curvature in three dimensions has been investigated using the finite difference approach (FLAC3D). An elliptical pit model with curvatures between 8 and 320 meters is modeled by geomechanical parameters of Choghart mine and has been analyzed under static load and a harmonic seismic load. The results obtained from the observation of co-elevation points on a single bench and elevation points show that static and dynamic displacement increases up to 2 times by increasing the radius of curvature and the dynamic acceleration increases up to 35 percent in larger curvature radiuses. The acceleration amplification factor (AF) has also been studied at different points and altitudes, the value of which varies between 0.3 and 1.2 depending on the radius of curvature.
 
Introduction
Evaluating the static and seismic stability of rock and soil slopes in civil and mining applications has been a significant concern for geotechnicians. The limited seismic studies have focused only on the parameters of the earthquake source, while, the site effects including topography and material stiffness contrast, have received less attention. Among topographical effects, a few studies were donated to the slope curvature and were mainly on the slope crest curvature in two dimensions. This study mainly focused on the topographical effect of the slope curvature in three-dimension.
 
Methodology and Approaches
In this research, an elliptical pit is simulated, using a 3D finite-difference code (Flac3D). The wall curvature radius (R) varies from 8 to 320 meters. The dynamic analyses were performed after verifying dynamic consideration under a harmonic seismic load representing the typical seismicity of the region, with a PGA of 0.5g and frequency of 5Hz. The displacement and acceleration of the models on one elevation and vertical direction were then monitored and plotted to observe the trend of displacement and acceleration versus curvature horizontally and vertically. Ultimately, the acceleration amplification factor variation was examined against curvature for both horizontal and vertical directions.
 
Results and Conclusions
 The static simulations showed that the displacement on a constant elevation for the pit would decrease 40 percent, from the curvature radius of 8 to 320 meters. This declination is due to the confinement stress in a smaller curvature radius. According to the dynamic analysis results, by increasing curvature radius on equal elevations, the displacement and acceleration would increase due to the steeper slopes at the points with a larger curvature radius. Where the acceleration would vary in the range of 0.4g to 0.55g.
The dynamic results show that the confining pressure has a greater effect on displacement than acceleration. Despite the lower acceleration at points with a smaller radius of curvature, a greater amount of displacement is recorded at these points. The main reason is the lower confinement pressure in these locations. Results depicted that the acceleration amplification factor (AF) would be a function of curvature radius, varying between 0.3 and 1.2, due to its concave geometry. 

کلیدواژه‌ها [English]

  • Slope Curvature
  • Amplification Factor (AF)
  • Seismic Analysis
  • Numerical Analysis

ایمنی و پایداری شیروانی­های معدنی و شیروانی­های جاده­ای به دلیل مخاطرات مالی و جانی از اهمیت ویژه­ای برای مهندسین ژئوتکنیک برخوردار است. با توجه به تنوع زیاد عوامل تأثیرگذار؛ مانند ویژگی­های مقاومتی سنگ یا خاک تشکیل‌دهنده، توپوگرافی، پارامترهای ژئومکانیکی ناپیوستگی­ها، شرایط آب­های زیرزمینی و لرزه­خیزی منطقه، انواع مختلف ریزش و شکست در شیروانی­ها محتمل است؛ بنابراین باید در محل­های مورد نظر عوامل فوق و تأثیراتی که به‌صورت مکمل عمل می­کنند بررسی شود. از طرفی به دلیل اهمیت بحث لرزه‌خیزی منطقه و زلزله در بحث پایداری شیروانی­ها لازم است طراحی لرزه­ای این سازه­ها از طریق "تحلیل خطر لرزه­ای" انجام گیرد. به‌طورکلی می­توان گفت دودسته عوامل پارامترهای منبع و عوامل محلی بر پایداری لرزه­ای شیروانی­ها تأثیرگذارند. پارامترهای منبع شامل بزرگی زمین‌لرزه، فرکانس لرزه، مدت‌زمان، فاصله افقی و عمودی شیروانی از منبع و ویژگی‌­های توپوگرافی منطقه هست. عوامل محلی نیز شامل توپوگرافی و تنوع ویژگی‌های ژئومکانیکی شیروانی است [1-4]. 

 
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