فهرست مطالب

مجله زمین شناسی مهندسی
سال دوازدهم شماره 2 (تابستان 1397)

  • تاریخ انتشار: 1397/05/10
  • تعداد عناوین: 8
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  • دلارا اشنویه، روزبه دبیری* صفحات 183-212
    پس از وقوع روان گرایی، نشست هایی در سطح زمین و درون لایه های خاکی ایجاد می شود که سبب آسیب رساندن به سازه های مستقر بر روی آن ها یا سازه های مدفون و شریان های حیاتی می شود. در دو دهه اخیر روش های نیمه تجربی مختلفی برای تعیین میزان کرنش حجمی (نشست) و کرنش برشی حداکثر بر اساس داده های صحرایی و آزمایشگاهیی ارائه شده است. هدف اصلی در تحقیق حاضر، مقایسه نتایج ارزیابی پتانسیل وقوع روان گرایی از دیدگاه شدت خطر وقوع و میزان نشست پس از وقوع روان گرایی در لایه های خاکی برمبنای استفاده از نتایج آزمون مقاومت نفوذ استاندارد (SPT)و سرعت موج برشی (Vs) در امتداد مسیر خط 2 متروی شهر تبریز است. در این تحقیق، ابتدا تعداد 54 حلقه گمانه در امتداد خط 2 متروی ذکر شده جمع آوری و بررسی شده است. سپس، پتانسیل روان گرایی در محدوده بررسی شده براساس روش های پیشنهاد شده انجام شده و شاخص خطر روان گرایی(LPI) درآن ها برآورد شده است. سپس میزان نشست احتمالی در لایه های خاکی ناشی از وقوع روان گرایی براساس نتایج حاصل از دو روش پیشنهادی انجام گرفته است. نتایج به دست آمده از تحقیق نشان می دهد که دو روش تطابق مناسبی نداشته و خطر وقوع روان گرایی حاصل از روش SPT در مقایسه با روش Vs دارای میزان کم تری است. هم چنین پیش بینی میزان نشست پس از وقوع روان گرایی در لایه های خاکی برمبنای روش سرعت موج برشی در مقایسه با روش آزمون مقاومت نفوذ استاندارد مقدار بیش تری دارد.
    کلیدواژگان: روان گرایی، نشست، خط 2 متروی تبریز، آزمون مقاومت نفوذ استاندارد (SPT)، سرعت موج برشی (Vs)
  • محمود بابالار*، علی رئیسی، جمال عبداللهی صفحات 213-236
    در این پژوهش اثر گازوئیل بر خواص فیزیکی و مکانیکی خاک رسی چسبنده بررسی شد. سپس تاثیر روش حرارتی و استفاده از دو نوع سورفکتنت بر مشخصات فیزیکی و مکانیکی خاک آلوده بررسی شد. خاک رسی چسبنده به صورت مصنوعی با درصدهای گوناگون گازوئیل ( 10% و 5%) آلوده شد. به منظور پاک سازی خاک به وسیله اعمال حرارت نمونه های خاک آلوده شده در معرض حرارت های 50، 100 و 150 درجه سانتی گراد قرار گرفت. علاوه بر آن پاک سازی با شوینده های سدیم دودسیل سولفات و تویین 80 نیز انجام شد. آزمایش های فیزیکی و مکانیکی شامل دانه بندی، حدود اتربرگ، تراکم و مقاومت تک محوری روی نمونه هایی از خاک طبیعی آلوده شده و خاک پاک سازی شده از دو روش گفته شده انجام شد. نتایج نشان داد افزودن گازوئیل موجب تغییراتی در مشخصات فیزیکی و مکانیکی خاک می شود و این تغییرات تابعی از درصد گازوئیل است. علاوه بر آن نتایج پژوهش ها نشان داد روش حرارتی و استفاده از شوینده در پاک سازی خاک موثر است.
    کلیدواژگان: گازوئیل، خاک چسبنده، پاک سازی، آلودگی، شوینده، روش حراراتی
  • سیامک بهاروند*، مهندس سلمان سوری، جعفر رهنماراد، مهندس مسعود جودکی صفحات 237-258
    حوضه آبریز وارک، یکی از زیرحوضه های رودخانه دز است که با مساحت 9/139 کیلومتر مربع در استان لرستان واقع شده است. این تحقیق با هدف تحلیل فعالیت زمین ساختی حوضه و هم چنین بررسی ارتباط خطواره ها با خطر زمین لغزش با استفاده از سنجش از دور و سیستم اطلاعات جغرافیایی انجام شده است. در این پژوهش از 4 شاخص مورفوتکتونیکی شامل گرادیان طولی رودخانه (SL)، منحنی هیپسومتری حوضه (HC)، پیچ و خم رودخانه (S) و عدم تقارن حوضه زهکشی (AF) استفاده و نتایج تجزیه و تحلیل آن ها با شاخصی تحت عنوان زمین ساخت فعال (Iat) بیان شده است. محاسبه شاخص زمین ساخت فعال نسبی نشان می دهد که منطقه از نظر تکتونیکی در کلاس فعال قرار دارد. به منظور بررسی ارتباط خطواره ها با خطر زمین لغزش، ابتدا نقشه خطواره ها و عوامل موثر بر لغزش با استفاده از پردازش تصاویر ماهواره ای لندست 8 در محیط نرم افزار ENVI 4.8 و بازدیدهای میدانی تهیه شده است. سپس با استفاده از روش منطق فازی نقشه خطر زمین لغزش در حوضه بررسی شده تهیه و با تلفیق آن با نقشه خطواره ها، ارتباط بین خطواره ها و نقشه خطر زمین لغزش در محیط نرم افزار Arc GIS بررسی شده است. بر اساس نتایج به دست آمده از نقشه خطر زمین لغزش های منطقه به ترتیب 40/12، 25/8، 37، 61/32 و 73/9 درصد از مساحت منطقه در کلاس های خطر خیلی کم، کم، متوسط، زیاد و خیلی زیاد قرار دارد. هم چنین نتایج به دست آمده نشان می دهد که به علت تکتونیک فعال منطقه ارتباط نزدیکی بین خطواره ها و مناطق با خطر لغزش بالا وجود دارد.
    کلیدواژگان: حوضه وارک، مورفوتکتونیک، خطواره، زمین لغزش، سنجش از دور، سیسنم اطلاعات جغرافیایی
  • محمود بهنیا*، مهندس جواد توکلی، مسعود چراغی صفحات 259-276
    در مدل سازی عددی با استفاده از روش المان مجزا، چگونگی ایجاد ناپیوستگی ها در مدل تاثیر زیادی بر نتایج نهایی مدل سازی دارد. در نرم افزار3DEC امکان ایجاد دسته درزه ها به چهار حالت منظم و مداوم، منظم و غیرمداوم، نامنظم و مداوم و نامنظم و غیرمداوم وجود دارد. از طرفی به دلیل تاثیر عمده ابعاد بلوک ها بر رفتار توده سنگ و پارامترهای مقاومتی و تغییرشکل پذیری آن، این که از چهار حالت موجود کدام مناسب تر است و بیان کننده شرایط واقعی توده سنگ است نکته مهمی است که باید به آن توجه شود. در این پژوهش از دیدگاه کمی موجود برای محاسبه شاخص مقاومت زمین شناسی (GSI) که کای و همکاران ارائه کرده اند و در آن ابعاد بلوک ها به عنوان پارامتری اثرگذار مورد نیاز است به منظور تعیین مناسب ترین حالت برای ایجاد درزه ها در مدل عددی بهره گرفته شده است. در همین راستا با استفاده از مشخصات سیستم ناپیوستگی های تکیه گاه چپ سد بختیاری و طبقه بندی GSI توده سنگ این ناحیه، مناسب ترین روش ایجاد دسته درزه ها در یک مدل عددی با توجه به فاصله داری و تداوم آن ها به گونه ای که ابعاد بلوک های تولید شده تطابق زیادی با ابعاد بلوک ها در واقعیت داشته باشد پیشنهاد شده است.
    کلیدواژگان: روش المان مجزا، نرم افزار3DEC، ابعاد بلوک ها، GSI، تداوم درزه ها
  • غلامحسین توکلی مهرجردی*، مهندس فریبا مترجمی صفحات 277-292
    ارزیابی پارامترهای مقاومت برشی خاک در پروژه های عمرانی و مباحث پایداری از دیرباز بسیار حائز اهمیت بوده است. در این پژوهش، به منظور بررسی تاثیر اندازه دانه های مصالح درشت دانه بر پارامترهای مقاومت برشی و رفتار اتساعی خاک، تعدادی آزمایش برش مستقیم بزرگ مقیاس در حالت خشک انجام گرفته است. متغیرهای این پژوهش شامل سه نوع خاک درشت دانه بد دانه بندی شده با میانگین قطر ذرات 3، 6 و 12 میلی متر، دو دانسیته نسبی 50 و 70 درصد و سربارهای قائم 100، 200 و 300 کیلوپاسکال بوده است. نتایج نشان می دهد که با افزایش اندازه دانه های خاک و دانسیته نسبی به دلیل افزایش قفل و بست بین دانه ها، تمایل به اتساع بیش تر شده و مقاومت برشی حداکثر نیز افزایش یافته است. به عبارت دیگر، مقاومت برشی نمونه ها با قطر میانگین 6 و 12 میلی متر نسبت به نمونه با قطر میانگین 3 میلی متر به ترتیب حدود 5 و 24 درصد افزایش داشته است. هم چنین افزایش اندازه دانه های خاک موجب افزایش نسبت مقاومت برشی ماندگار به مقاومت برشی حداکثر شده و خاک به افت مقاومتی کم تری دچار شده است، به موازات آن زاویه اصطکاک داخلی، حداکثر زاویه اتساع و زاویه اصطکاک در حجم ثابت، افزایش یافته است.
    کلیدواژگان: خاک درشت دانه، اندازه دانه های خاک، دانسیته نسبی، پارامترهای مقاومت برشی، زاویه اتساع
  • مسعود زارع نقدهی، سید داود محمدی*، مصطفی کریمی صفحات 293-314
    اولویت بندی روش بررسی زیرسطحی نقش مهمی در مدیریت اقتصادی و ایمنی پروژه های زیرزمینی دارد. در این پژوهش شیوه جدیدی برمبنای فرآیند تحلیل سلسله مراتبی (AHP) و شباهت به گزینه ایده آل (TOPSIS) برای اولویت بندی روش های بررسی مسیر تونل سبزکوه از میان طیف گسترده ای از روش های ژئوتکنیکی و ژئوفیزیکی پیشنهاد شده است. برای این کار ابتدا مهم ترین عامل موثر بر انتخاب بهترین روش بررسی زیرسطحی این پروژه بررسی شده و سپس با به کارگیری روش تحلیل سلسله مراتبی (AHP) عوامل بررسی شده به صورت زوجی مقایسه و وزن هر یک از عوامل محاسبه شده است. علاوه بر این، از روش شباهت به گزینه ایده آل برای انتحاب نزدیک ترین روش به حالت ایده آل بررسی زیرسطحی مسیر تونل سبزکوه بهره گرفته شده است. در نهایت از بین 6 گزینه بررسی زیرسطحی پیشنهاد شده برای تونل، در هر دو روش AHP و TOPSIS پژوهش های لرزه ای به عنوان بهترین گزینه، و بقیه گزینه ها با توجه به وزن مورد نظر در اولویت های بعدی قرار گرفتند.
    کلیدواژگان: زاگرس، تونل سازی، تصمیم گیری چندمعیاره، روش سلسله مراتبی، روش شباهت به گزینه ایده ال
  • امید نعیمی فر*، سید شهاب الدین یثربی صفحات 315-344
    تاثیر بافت اولیه و درصد ریزدانه خمیری روی رفتار ماسه های رسدار بررسی شده است. برای مدل سازی بافت اولیه نمونه در شرایط نهشته گذاری مختلف از چهار روش نمونه سازی درآزمایش های سه محوری استاتیکی و سیکلیک استفاده شده است. آزمایش ها روی ترکیبات ماسه با صفر تا 25 درصد ریزدانه که با چهار روش تراکم مرطوب، ریزش خشک، ته نشینی در آب و ریزش جریانی ساخته شده اند و تحت بارگذاری های استاتیکی و سیکلیک انجام شده است. نتایج نشان دهنده آن است که روش های ته نشینی در آب و ریزش جریانی و ریزش خشک تمایل به تولید بافت های اتساعی دارند که حتی با افزایش درصد ریزدانه خمیری نیز هم چنان رفتارهای اتساعی خود را حفظ می کنند. در مقابل روش تراکم مرطوب تنها در حالت ماسه تمیز از خود رفتار اتساعی نشان می دهد و با افزایش درصد ریزدانه به سرعت به سمت ناپایداری و بروز رفتارهای نرم شوندگی کامل با کرنش می رود. در حالت بارگذاری سیکلیک تفاوت بین روش ها کم تر شده و با افزایش درصد ریزدانه به نظر می رسد رفتارهای مشاهده شده برای روش های مختلف به سمت یک روند یک سان میل می کنند. به صورت کلی با افزایش درصد ریزدانه خمیری تا حدود 20 درصد ناپایداری در نمونه های تحت آزمایش افزایش یافته است و بعد از آن مجددا نمونه ها به سمت پایداری بیش تر حرکت می کنند. نکته قابل توجه آن است که نوع روش نمونه سازی و بافت اولیه نمونه تاثیر خاصی روی این حد آستانه نداشته است.
    کلیدواژگان: تراکم مرطوب، ریزش خشک، ریزش جریانی، ته نشینی در آب، سه محوری، درصد ریزدانه خمیری
  • ساسان نریمان نژاد، علیرضا جعفری ندوشن، علی معصومی*، عبدالله سهرابی بیدار، علی قنبری صفحات 345-372
    از آن جاکه اغلب شهرها در نزدیکی و یا روی دره های آبرفتی بنا شده اند، اثرهای هندسه حوضه رسوبی بر حرکت زمین در مهندسی ژئوتکنیک لرزه ای اهمیت ویژه ای دارد. انحنای حوضه ای که در آن خاک های آبرفتی نرم تر رسوب گذاری شده است، می تواند امواج حجمی را حبس کرده و موجب می شود که برخی از امواج حجمی برخوردی، به صورت امواج سطحی در لایه آبرفتی منتشر شوند، این امواج می توانند لرزش های شدید تر و طولانی تری نسبت به آن چه در تحلیل یک بعدی با فرض انتشار قائم امواج برشی تخمین زده می شوند ایجاد کنند. در این پژوهش با استفاده از نرم افزار المان محدود آباکوس چهار شکل حوضه رسوبی شامل مستطیلی، ذوزنقه ای، بیضی و مثلثی در حوزه زمان تحلیل شدند و اثر شکل هندسی حوضه رسوبی و هم چنین اثر محتوای فرکانسی موج تحریک در هر یک از حوضه ها بررسی شد و نتایج آن با تحلیل یک بعدی مقایسه شد. نتایج نشان می دهد پاسخ های تحلیل یک بعدی با دو بعدی اختلاف بسیاری دارد این اختلاف تا 45/1 برابر پاسخ شتاب تحلیل دوبعدی به یک بعدی در حوضه مستطیل شکل است. مدل حوضه مستطیل شکل که در این تحقیق بررسی شده است در مقایسه با سایر حوضه ها پاسخ های بیش تری دارد.
    کلیدواژگان: اثر ساختگاه، اثر توپوگرافی، حوضه رسوبی، دره آبرفتی، بزرگ نمایی، ژئوتکنیک لرزه ای، حرکت حوزه آزاد، مرزهای جاذب انرژی، المان محدود
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  • Delara Oshnaviyeh, Rouzbeh Dabiri * Pages 183-212
    Introduction
    When loose sand is subjected to seismic shaking, it tends to volume reduction and settlement. The density of the under layers is revealed in the settlement of the ground surface that causes the destruction of the structures located on ground surface. In dry sand layer, settlement in severe shakings occurs under a constant and effective stress condition and very rapid stress. In this regard, the sand deposit settlement is completed before the end of an earthquake, but if the sandy soil layer is saturated and drainage is limited the condition is prepared of fixed volume situation and the major effect of the seismic shocks is generation of exceed pore water pressure. Therefore, the deposit settlement of saturated sand requires a longer time, varying from a few minutes to a few days, depending on the permeability and compressibility of the soil and the length of the drainage path. The main purpose of the present study is to evaluate liquefaction hazards along Tabriz Metro Line 2 with using Standard Penetration test (SPT) and shear wave velocity (Vs) methods. Also, the probable rate of settlement in the soil layers in study area and correlation with liquefaction potential index (LPI) according to both procedure have been determined and discussed in the following paragraphs.
    Material and
    Methods
    In order to evaluate the liquefaction potential of soils using two field methods, geotechnical information of 54 boreholes in Tabriz Metro Line 2 were collected. The types of soil and geotechnical properties can affect the liquefaction potential. In this study, the gravely sand, silty sand, silty and sandy soils were studied. Ground water level is one of the main parameters in in soil liquefaction potential evaluation of soils. Variation of water level in boreholes is 2 to 30 meters. The peak ground acceleration (PGA) is necessary for the analysis of boreholes to evaluate liquefaction potential of soils. PGA values were selected in each boreholes position according to the Iranian Code of Practice for Seismic Resistant Design of Buildings (Code-2800-ver.4) equal to 0.35g (for return period 475 years and design life 50 years). Liquefaction potential of soil layers based on SPT results with appliying Idriss and Boulanger (2010) method has been assessed. Andrus, Stokoe and Jung (2004) procedure was used in shear wave velocity (Vs) method (with assuming cementation and un cementation condition in soils). Liquefaction potential index (LPI) of soil layers was calculated for both field tests results. Then, probable rate of settlement due to liquefaction in saturate soil layers was determined. Tokimatsu and Seed (1978) method applied for SPT results, Yoshimine (1992), Yoshimine et al. (2006) and Yi (2009) procedures have been used in Vs test. Finally, correlation between rate of settlement and LPI results were determined.
    Results And Discussions
    Outcomes of this study can be explained in below: 1. Results obtained from comparison of both methods in liquefaction potential evaluation have been showed, agreement between two methods have been happened rarely. Specially, with assuming cementation condition in soils, LPI obtained from Vs method is more than SPT. Although, different factors can be affected at uncertainties in SPT results such as type of drilling machine, energy efficiency and accuracy of test performing. Also, in shear wave velocity method, maximum velocity for occurring liquefaction in soil layers () related to fines content percentage. It is possible that boundary values in procedure not compatible with geotechnical properties in study area.
    2. Evaluation of probable rate of settlements in soil layer in study area have been showed that settlement values obtained from Vs is more than SPT. This condition is compatible with LPI amounts.
    Conclusions
    In sum up, settlement due to liquefaction in saturate soil layers is one of the important phenomena in geotechnical earthquake engineering. Maximum rate of settlement in soil layers in study area is equal 0.45m based on SPT method and 0.9m according to Vs procedure which should be considered. Accordingly, serious damages can be inflicted to buildings, underground structures and life lines in study area. Therefore, it is suggested in future researches with using empirical and numerical (or soft computing) methods based on field and experimental tests results a detailed assessment conducted and influence of various parameters on settlement of soil layers be determined and the items listed below should be considered: - Cementation parameter (C) values of soils in shear wave velocity method maybe not compatible with geotechnical properties in study area. It should be evaluated exactly.
    - In this research, peak ground acceleration (PGA) value was selected based on code 2800-ver.5. As regard to Tabriz Metro Line 2 is beside to Tabriz North Fault, PGA value according to historical earthquake catalogue and seismic risk analysis should be evaluated and seismic hazard have to determine with accuracy.
    Keywords: Liquefaction, Settlement, Tabriz Metro Line 2, Standard Penetration Test (SPT), Shear wave velocity (Vs)
  • Mahmoud Babalar *, Ali Raeesi Estabragh, Jamal Abdolahi Pages 213-236
    Introduction
    Contaminants can be categorized into organic and inorganic groups. Organic contaminants are carbon based, and their presence in waste forms may be as a single contaminant associated with inorganic contaminants, or a suite of complex mixtures which may be toxic at very low concentrations. Organics of greatest environmental concern are usually refined petroleum products, chlorinated and non-chlorinated solvents, manufactured biocides, organic sledges and substances from manufacturing processes. Most contamination due to organics are associated with accidental spills and leaks, originating from equipment cleaning, maintenance, storage tanks, residue from used containers and outdated material (Yong and Mulligan, 2004). Transport and fate of organic contaminants are important. Organic contamination migrations are due to advection (by fluid flow through soil) and diffusion, but other forms of transport e.g. infiltration may also contribute to migration (Environment Agency, 2002). The response of the soil to a contaminant depends upon the type of soil and the nature of the contaminant. The sensitivity of soil to contaminants depends upon the type of soil (such as particle size, mineral structure, bonding characteristics between particles and ion exchange capacity) and the nature of contaminants. Fang (1997) defined a sensitivity index (ranging from 0 to 1) to different types of soil. Sensitivity of sand and gravel (0.01 to 0.1) is much lower than clay particles (0.6-0.9). There are a number of techniques for remediation of contaminated land. These include physical (washing, flushing, thermal, vacuum extraction, solvent extraction), chemical (stabilization and solidification) and bioremediation techniques. However, the applicability and feasibility of different methods for remediation are dependent on many factors such as soil characteristics (soil type, degree of compaction and saturation), site geology, depth of contamination, extent of contaminant in lateral direction, topography, surface and ground water and the type and amount of contaminants. Thermal treatment and using surfactants are the most popular methods for remediating the soil contaminated with petroleum compounds. In this research remediation of a soil contaminated with different percentages of gasoline was studied through physical techniques in laboratory. The applied physical techniques were thermal technique and use of two different kinds of surfactants. The obtained results were compared with each other and discussion was performed.
    Material and
    Methods
    Soil, gasoline and surfactant are the basic materials that were used in this work. The soil that was used in this testing program was a clayey soil. Two different types of ionic and nonionic surfactant, namely Tween 80 and SDS, were used in this work for remediating soil, contaminated with gasoline. Contaminated soil was prepared by adding 5 and 10 % weight (to air dried soil) of gasoline. 6 kg air dried soil was selected and the desired amount of gasoline was weighted, then it was sprayed on the soil and thoroughly mixed by hand for about 2 hours. The prepared mixture was kept inside a covered container for a week in order to come to equilibrium with the soil. For thermal remediation the contaminated soil with a specific percent of gasoline was kept inside a constant convection oven at 50, 100, and 150oC for about one week to desorb the contaminating compound. Tween 80 and SDS were used for remediation of the contaminated soil. The amount of used Tween 80 was 25% weight of contaminating compound and selection of SDS amount was based on 50% weight of contaminating matter. The samples for the main tests were prepared by static compaction according to the optimum water content and maximum dry unit weight that were obtained from standard compaction tests. Atterberg limits, grain size distribution, compaction and unconfined compression tests were performed on samples of natural, contaminated and remediated soil according to the ASTM standard.
    Results And Discussion
    The results of Atterberg limits (LL, PL and PI) for the contaminated soil (with 5 and 10 % gasoline) indicated that the values of them are increased with increasing the percent of gasoline. These values are nearly the same as natural soil after remediation with thermal method and surfactants. The grain size distribution curves were determined for the natural soil, contaminated soil with 5% and10% gasoline and soil remediated by thermal and surfactant techniques. The results showed that by using thermal technique the percent of clay is decreased and the percent of sand and particularly silt is increased by increasing temperature. The results of grain size distribution for the soils remediated by SDS and Tween 80 showed that the percent of clay is reduced but the percent of silt and sand are increased. Comparing the results of the two surfactants shows that the effect of Tween 80 in reduction of the percent of clay is more than SDS. The results showed that after thermal treatment, the maximum dry unit weight decreases and the optimum water content increases. For the contaminated soil with gasoline a reduction in maximum dry unit weight is observed compared with natural soil. The effect of SDS and Tween 80 on soil remediation is reduction in maximum dry unit weight and optimum water content. The results of compression strength showed that adding gasoline to soil causes a reduction in final strength and this reduction is a function of gasoline percent. The results also indicated that the strength of remediated soil by thermal or surfactant techniques, is reached nearly to the strength of natural soil. Scanning electron microscopy (SEM) tests were performed on the samples in order to observe the microstructure of the samples in different conditions (natural and contaminated with different percent of gasoline). The results of SEM showed that the structure of soil is changed by contamination to gasoline. It can be said that the gasoline causes reduction in the thickness of DDL because of low dielectric constant and hence a flocculated structure is formed. In the flocculated structure due to attractive forces, the fine particles paste to each other and form coarse particles. Therefore, variations in the Atterberg limits and compaction parameters can be resulted from forming new structure by adding gasoline. These results of compression strength are not in agreement with the theory of diffuse double layer (DDL). The reduction in dielectric constant would cause a flocculated structure in soil and the strength of the contaminated soil should be increased in comparison with the natural soil. It can be said the viscosity of gasoline cause reduction in the strength of contaminated soil.
    Conclusion
    In this experimental work a cohesive soil was contaminated with 5% and 10% of gasoline. The experimental tests showed that the properties of contaminated soil are different from natural soil and the change in the properties is a function of gasoline percent. The contaminated soil, was remediated by thermal treatment and also using two surfactants. The results also showed that using surfactants is more effective than using thermal method in soil remediation, and can treat the soil nearly to its original condition.
    -Base on the SEM analysis results, adding gasoline to the soil, will change the soil micro structure to a flocculated one.
    -The gradation curves show that adding gasoline to the soil will change the gradation from finer to coarser.
    - Contamination to gasoline will change the compaction parameters of the soil, and will reduce the soil final strength significantly.
    - The results show that using thermal method and surfactants is effective in remediating the soil, but it is more effective to use surfactants.
    Keywords: Gasoline, Cohesive clay, soil remediation, Contamination, Surfactants, Thermal method
  • Siamak Baharvand *, Salman Soori, Jafar Rahnamarad, Maseoud Joudaki Pages 237-258
    Introduction
    Earth is a dynamic system. Change is one of its features. At its surface, there is almost no region that over the past few thousand years has not affected its neotectonic activities. In fact, it can be said that active neotectonic is changing the surface of the earth. Among geological methods for analyzing active tectonic movements, deciphering the geomorphology and morphotectonic nature play a very important role, because many geomorphic complications are sensitive to active tectonic movements and the geometric analysis of these complications provides evidence of the type, rate, and configuration of active tectonic deformations. Moreover, these geomorphic indices at a regional scale provide basic reconnaissance tool to identify tectonically active regions, their susceptibility to tectonic deformation, and level of tectonic activity.
    In the presented study, tectonic activities and geological structural features of the Vark basin in Lorestan province, such as the discontinuities that may be detected on satellite imagery as lineaments, and in many cases control landslide occurrences, have been analyzed using the GIS and remote sensing.
    Material and
    Methods
    Neotectonic investigation in the area: in order to analyze and to evaluate the tectonic movements in the Vark basin, considering the validity of geomorphic indices, longitudinal gradient (SL), river meanders (S), basin hypsometric curves (HC) and asymmetry factor (AF) have been used. After calculating the desired indices, the tectonic activity of the area has been evaluated using the index of active tectonic (IAT).
    Vark basin lineaments map derived from satellite images with proper resolution: using remote sensing techniques and visual interpretation of the OLI Landsat 8 satellite imagery, all fractures and lineaments of the region were identified and then by preparing the rose diagram, the trend of the lineaments of the area analyzed.
    Landslide hazard zonation in the Vark basin: In this study, in addition to plotting landslide occurrence Points, eight other factors were also investigated. In order to provide a map of the factors affecting slip, the digital elevation model (DEM) in ENVI 4.8 and ArcGIS soft wares were used and the maps of slope, slope aspects, altitude classes, area geology, land use, topography and precipitation were prepared. Then, in order to zoning the landslide hazard, fuzzy logic method has been used. Fuzzy logic is based on the fuzzy layers and the fuzzy inference process.
    Results And Discussion
    Analyzing the Neotectonic of the Area: as stated above, the relative active-Neotectonic (IRAT) index is derived from the interpolation of the morphotectonic indexes. In this case, after reviewing the morphotectonic indices of the study area and determining the activity rate of each indicator, the classification or prioritization of these activities were done. The results obtained from calculating the active tectonic index indicate that the study area with IAT is equal to one, has an active neotectonic.
    Preparing the Lineation Maps of the Area: in this research, the aim of the data processing including satellite imagery and digital elevation model is identification and extraction of fractures and faults in the Vark basin. To this end, we can use the integration of the information layers derived from the above processes. In this step, all layers of information are logged into the ArcGIS software so that their overlap can provide a map of fractures and faults. On each information layer processed there is a series of lineaments recognizable that can be visually distinguished. After extraction of lineaments by comparing them with bundle compounds and maps derived from digital elevation model and geological map of the region, the lineaments of fractures and faults were separated from other lineaments and their shape file map has been prepared. In order to plot the rose diagram of fractures and faults, the Polar Plots ArcGIS Extension was used. The results obtained from this rose diagram showed that the dominant trend is the northwest southeast followed the trend in the region.
    Preparing a map of landslide hazards zoning in the region and investigating its relationship with the lineaments: In order to overlap layers affecting the area's landslide hazard, Gamma fuzzy operator (λ= 0.9) has been used and landslides hazard mapping prepared. Based on the results, 12.40, 8.25, 37, 32.61 and 9.73 percent of the area are located in the very low, moderate, high and very high-risk classes, respectively.
    In order to investigate the relationship between the lineaments and the landslide hazard maps as parameters that are affected by the tectonic activities of the area, the lineaments map was integrated with the map of landslide hazard. The results show that the most of lineaments identified in the study area have a northwest-southeast trend that are similar to the main faults of the region and Zagros. It can therefore be said that the lineaments are influenced by the faults and folds mechanism of the region. According to the lineament density in areas in places that are exposed to landslides, one can understand the close relationship between the lineaments and the landslide.
    Conclusion
    Based on the results obtained from relative active tectonics index, the Vark basin has an active neotectonic, which leads to an uplift in parts of the basin, as well as tilting in the southern part of the area.
    In this research, the tectonic of the area, and then the relationship between the lineaments and the map of the landslide risk, as two phenomena affected by active neotectonic were reviewed. Investigating the lineaments of the region shows that the dominant trend is fractures north-west-south-east and following the trend in the region. In addition, analyzing the relationship between the lineaments with the map of the landslide hazard of the area shows that there is a close relationship between the lineaments and the zones with high risk of slipping.
    Keywords: Vark basin, Morphotectonic, Lineaments, Landslide, Remote sensing, GIS
  • Mahmoud Behnia *, Javad Tavakoli, Masoud Cheraghi Seifabad Pages 259-276
    Introduction
    The rock block volumes are formed due to the intersection of discontinuities in the jointed rock mass. The block dimensions affected by joint spacing, joint orientation, joint sets, are taken to be the most important parameters determining the rock mass behavior, strength parameters, and deformations. In the numerical modeling using distinct element method, the creation of the discontinuities can affect the final results very much. Using 3DEC software, it is possible to create joint sets in four conditions: regular and persistent, regular and non-persistent, non-regular and persistent, irregular and non-persistent. As an important point to consider, the major effect of block dimensions on rock mass behavior, strength parameters and deformation modulus can help to decide which one is most suitable to indicate the real conditions of rock mass. As explained in the previous studies, the use of persistent joints leads to the block dimensions being considered as small ones. In this way, due to the high strength of intact rock compared to the joints, the possibility of instability increases.
    Material and
    Methods
    In this research, from quantitative point of view, Geological Strength Index (GSI) is calculated, based on block dimensions as an influential parameter, to consider the most appropriate case for creating joints in the numerical method. In this regard, according to valuable studies in Bakhtiari dam structure, the characteristics of discontinuities system and GSI of rock mass are utilized to come up with real conditions. Then, the modeling is done with different conditions of joints, block volume distribution, GSI for each case, and the results are compared with quantitative ones. And then the most suitable case for creation of joints in numerical modeling is suggested by using 3 DEC software, regarding the blocks volumes, type of distribution function, and GSI value. Also, the accuracy of this finding is investigated for other structures, independently of input parameters, by making changes in spacing, and joints persistence as two effective parameters in rock blocks dimensions. Owing to the difficulty in the accurate definition of joints persistence, which is related to dimensions of the location, the numerical models for joint persistence are done in an acceptable level in order to create blocks with high conformity in terms of the dimensions. Then, the comparison is made between block dimensions from perspectives of numerical models and GSI values, to choose the best ones showing high conformity with real conditions.
    Results And Discussion
    The comparison of the modeling results using creation of joints in different cases with quantitative results obtained according to geological strength shows that the created block volumes are not properly distributed due to the creation of joints as irregular ones in the two cases of persistent and non-persistent. In this case, the blocks volume changes from a few centimeter to cubic meter, and as the block dimensions increase, the created blocks become bigger. Thus, according to the created blocks volume and the obtained GSI range, the creation of joints is not a suitable method as an irregular one. The creation of regular and persistent joints is not an appropriate method either, as the most created blocks are small, and blocks volume distributions do not comply with quantitative distribution. But with creation of joints as regular and persistent ones, the distribution function of blocks volume in numerical method and quantitative method is log normal. Therefore, according to the created blocks dimensions and GSI range using 3DEC software, the most suitable case is the creation of joints as regular and non-persistent ones.
    Conclusion
    According to the obtained results in the four cases, when the joints are considered only as regular and non-persistent ones, the blocks volume range is more compatible with real conditions and follows log normal distribution. Thus it can be concluded that the suggested method for creation of joints in the numerical modeling using 3DEC software is more suitable than others considering the rock blocks dimensions and their distributions. This method can be utilized in any structure to accurately define the persistence of joints regarding created blocks dimension.
    Keywords: Distinct Element Method, 3DEC software, blocks dimensions, GSI, persistence of joints
  • Gholamhosein Tavakoli Mehrjard *, Fariba Motarjemi Pages 277-292
    Introduction
    The general failure mechanism of soil element in geotechnical structures is shear failure under static and dynamic loads. Therefore, assessment of soils’ shear strength parameters is very crucial in the performance of geotechnical structures, especially in slope stability. Tavakoli Mehrjardi et al. (2016) showed that by increasing soil grain size in unreinforced soil masses, bearing capacity of foundation increases due to increasing shear strength parameters of soil mass. Furthermore, Tavakoli Mehrjardi and Khazaei (2017) found out that generally, for all reinforced and unreinforced conditions, cyclic bearing capacity was enhanced by increasing the medium grains size of backfills. Taking into account the deficiency of studies on the shear characteristics of soil, a series of large direct shear test have been carried out to investigate and to compare effects of the soil’s physical properties such as aggregate size and relative density, besides of normal stress, on the shear characteristics of the backfills.
    Material and Test Program: In this study, three types of uniformly graded soils as fill materials with the medium grain size (D50) of 3, 6 and 12 mm were considered. These soils are classified as SP and GP in the Unified Soil Classification System. It should be mentioned that these materials can be used in railroad as ballast and in retaining walls as fill materials. The current study aims to investigate strength characteristics of the backfills, influenced by different parameters such as relative density of the fill materials, normal stress on the shear plane and aggregate size of the fill materials. To cover all the matters, 18 large-scale direct shear tests have been scheduled. These tests encompass two relative densities of fill materials (50% and 70% which represent medium dense and dense backfill, respectively), three aggregate sizes of fill materials (3, 6 and 12 mm- selected based on the scaling criteria on size of shear box) and three normal stresses (100, 200 and 300 kPa- these values cover rather low to high vertical stress in a soil element of common geotechnical projects) have been examined. It should be mentioned that, prior to shearing, the normal stress was applied to the specimens for a period of 1 h, in order to stabilize the soil particles from any possible creep. As all materials used in this research are of coarse-grained type and the experiments were performed under dry conditions, the displacement rate of 0.5 mm/min was selected. During the tests, the applied normal stress, displacement of the lower box, shear force mobilized at the interface and vertical displacements of the cap were continuously recorded.
    Results And Discussion
    The curves of shear stress as a function of shear displacement and also shear displacement-vertical displacement for samples show that shear stress dropped down to a specific amount of residual shear strength after reaching maximum amount of shear stress . It was observed that increasing the particle size and relative density of the fill materials mostly fortify interlocking of the grains which in turn, resulted in increasing the tendency to expansion through the shear plane. On the other hand, the initial compression has decreased and dilation was started from a smaller shear displacement. This may be interpreted that as the soil particles size increases, more expansion is required to reach the maximum shear strength. Moreover, comparing the observed behavior, it is found out that unlike the effect of grain size and density, increasing the normal stress caused the materials to be more compressed, resulted in reducing expansion and increasing the initial compression of the soil mass. This conceivably means that increasing normal stress, transferred on shear plane, can change the failure mechanism of materials, from dilatancy failure to bulging failure under shearing. From the results, it was found out that increasing medium grains size of soil from 3 mm to 12 mm ended to improvement in the maximum friction angle at relative density 50 and 70% by the value up to 4.4 and 5.8 degree, respectively. In fact, due to increasing grain size, the grains interlocking have been fortified. In order to have a comparison, the maximum dilation angles of all fill materials, mobilized at the shear plane, have been derived. Accordingly, the maximum dilation angle was increased with the increment of the fill grains size and relative density of the material. Nevertheless, by considering variation of peak dilation angle with normal stress, it is found out that the normal stress had a negative influence on the advancement of interface’s dilation angle. These findings can be directly interpreted by considering the compression/expansion of the materials during the increment of shear displacements.
    Conclusion
    The current study, consists of 18 large-scale direct shear tests, aims to investigate shear characteristics of soil which influenced by different parameters such as relative density of the fill materials, normal stress at the shear plane and aggregate size of the fill materials. Eventually, the following conclusions are presented: •Increasing relative density, soil particle size and normal stress have beneficial effect in shear strength improvement. But, the mechanisms of each parameter in this enhancement is different.
    •The dilation rate of shear interfaces directly complies with changes in the ratio of applied shear stress to vertical stress. So, the maximum dilation angle and the maximum ratio mobilized at the shear plane have occurred around the same shear displacement.
    •Maximum values of friction and dilation angels have been occurred around the same shear displacement. Moreover, compaction effort leads to increase the required shear displacements to approach the maximum shear characteristics.
    Keywords: Aggregates, Soil particles size, Relative density, Shear strength's parameter, Dilation angle
  • Masoud Zare Naghadehi, Seyed Davood Mohammadi *, Mostafa Karimi Pages 293-314
    Introduction
    The selection of the best subsurface exploration methods corresponding to geotechnical, topographical and economic circumstances of the project is one of the most effective factors in the success of a tunneling project. On the other hand, the development of a decision model and consequently choosing the most suitable alternatives are complex tasks. Therefore, prioritizing and selecting the best subsurface exploration methods, as the main aim of this study, can reduce the economic and social costs associated with the execution of a tunneling project. For this purpose, ten experts from tunneling community have been asked to weigh the chosen criteria of the problem in this research. A methodology utilized in this study is the Analytical Hierarchy Process (AHP) which proved useful in engineering decision-making problems. The other method is TOPSIS, one that has continuously been used in decision making in the recent decades. These two techniques have been combined and utilized in this work to rank the aforementioned exploration methods.
    Material and
    Methods
    The study area is located about 109 km far from Shahrekord city amid the Zagros mountains. The Sabzkooh tunnel development plan has been under evaluation in the time that this research was being done. The geology of the area majorly encompasses sedimentary rocks which have been outcropped as folds, faults, and fractured and altered zones. However, the variety of the lithological units in the tunnel route is high, and units of limestone and shales also exist over the path.
    In the first step, geological and topographic maps were produced for the study area, and general information from the tunnel path was collected and examined. Suitable exploration methods were evaluated, and six main methods were chosen to be considered as the alternatives of the study including (a) discontinuities study, (b) Lugeon tests, (c) RQD, (d) Geo-electric, (e) Gravimetry, and (f) Seismic methods. Moreover, nine criteria ranging from “volume of the available information” and “environmental impact” to “cost” and “accuracy” of the employed methods were taken into account. A pairwise comparison matrix was then developed, and the experts were asked to fill it out. The importance of each criterion was then simply calculated through this matrix. Alternatives pairwise comparison matrices were also filled out and, in this manner, the alternatives could be ranked using the AHP technique. Next, the TOPSIS technique was employed for the same purpose using a rather different process.
    Results And Discussion
    Both AHP and TOPSIS techniques show very close results for ranking of the alternatives in this study. They rank the three Seismic, Geo-electric and Discontinuities studies methods as the best ones for the considered tunneling project. The only difference between these two techniques is how they determine the worst method. The AHP ranks the Lugeon as the last rank among the six methods whereas the TOPSIS determines the RQD as the least reliable method of exploration for the Sabzkooh tunnel project.
    Conclusion
    The prioritization and the subsequent selection of the most reliable exploration methods for an underground excavation project is a crucial task amid technical decisions. In this research, two major multi-criteria decision-making methods including AHP and TOPSIS were considered and applied for the Sabzkooh tunnel in Iran. The results indicate a high agreement between the two methodologies even though these two approaches decide differently on the least reliable methods to be applied.
    Keywords: Decision making, Exploration methods, Tunnel excavation, Reliability
  • Omid Naeemifar *, S.Shahab Yasrobi Pages 315-344
    of initial texture and plastic fine content has been investigated. In order to model the different deposition condition four different specimen preparation methods are used. The tests are conducted on sands and its combination with to 25 fine percent using static and cyclic method. Four different specimen preparation methods are used consisting of Dry Funnel Deposition (DFD), Water Sedimentation (WS), Moist Tamping (MT) and Air Pluviation (AP). Each method may be useful to model the behavior of some special deposited soils. For example, DFD is the best method to model the natural deposition of silty sands, while the WS method is suitable for simulating the sands natural deposition in the rivers. MT method is the best method to simulate the behavior of compacted embankments while SD method is suitable to prevent the segregation of particles with respect to other methods like Water Pluviation. Effect of sample preparation methods on the sands and silty sands behavior is investigated to some extent, while the clayey sands are rarely considered. The results show that water sedimentation method, Air pluviation method and Dry funnel deposition method tends to create dilative textures with continuous dilative behavior even in high clay fine content. In contrast, the wet tamping method shows the dilative behavior only for clean sands specimens and increasing fines will results in instability and complete strain softening behavior. In cyclic loading the difference between different methods are less with respect to static loading. It seems that the results of different methods tends to be identical with increasing in fine content. In general, increasing fine content up to 20 percent results in more instability. After that a threshold value can be estimated bout 2 percent, after that the instability becomes less with continuous increase in fines content. The valuable result is that the threshold value is not dependent on the specimen preparation method or initial texture of specimens.
    Keywords: Wet Tamping, Air pluviation, Dry funnel deposition, Triaxial, Water sedimentation
  • Sassan Narimannejad, Alireza Jafari-Nedoshan, Ali Massumi *, Abdollah Sohrabi-Bidar, Ali Ghanbari Pages 345-372
    Introduction
    Local site conditions considerably influence all characteristics of the ground strong motion including the domain, frequency content, and duration. The level of such an effect could be considered as a function of geometry, properties of the materials embedded in the underlying layers, the site topography, and properties of excitement. Site effect fall into two categories: a) the effect of the surface soft layers triggered by the shear velocity differences between the soil layers and b) the surface and subsurface topography effects that lead to the wave reflection and refraction based on the site geometry, and subsequently enhance the level of amplification.
    Since most cities have been constructed in the vicinity of or on sedimentary basins, geotechnical earthquake engineering devotes particular attention to effects of the sedimentary basins. Basin edge curvature deposited with soft soils are capable to trap the body waves and generated surface waves within the deposit layers. Such waves could create stronger and lengthier vibrations than those estimated in a 1D analysis that assumes the shear waves to be vertically propagated.
    Although critically important, the 2D effect of the site has not been included in seismic codes and standards of the world. This might be due to the fact that the site effect depends on a number of parameters such as the site geometry, the type of wave excitement, properties of the materials, etc. that in return make it almost out of the question to make predictions about the effect. This study was an effort to compare the responses of four sedimentary basins with hypothetical geometries of rectangular, trapezoidal, elliptical, and triangular shapes in order to examine the effect of the geometrical shape of the basin on its responses and the extent of the response sensitivity to the excitation frequency of the wave. The study assumed the edge to depth proportion to be both constant and equal in all four basins so that the effect of the geometrical shape could be equally examined and compared in all four basins.
    Material and
    Methods
    In order to validate the results of the sedimentary basin modeling, firstly, ABAQUS finite element software was used to create a free field motion of a semi-circular alluvium valley in accordance with Kamalian et al. (2006) and Moassesian and Darvinsky (1987). Then, the results from the model were compared with those from the above mentioned studies. The following descriptions are to present the model in details.
    To evaluate the geometrical effect of the sedimentary basin on its response, the authors relied on the software to examine four sedimentary basins with the fundamental frequency (2.04 Hz). The basins enjoyed rectangular, trapezoidal, elliptical, and triangular geometrical shapes with a constant edge to depth proportion (49m to 300m respectively). The implicit method was also applied to perform the dynamic analysis. The materials were all viscoelastic and homogeneous. The soil behavior/treatment model was considered to be of a linear nature. The Rayleigh damping model was used to specify the damping level. The soil element was a plane strain and SV waves (the Ricker wavelet) were used for seismic loadings in a vertical dispersion. The side boundaries (right and left) of the model were of a combinational type (viscous and free field boundaries); the down side boundary was composed of viscous. To achieve higher levels of wave absorptions, heavy columns were used as the free filed columns.
    Next, it was the time to conduct the 1D analysis of the site. Three waves were in use in order to examine the effect of the frequency content of the excitation load on the basin response: 1) a wave with the dominant frequency of 1Hz that was out of the frequency range of all basins (2.04 Hz), a second wave with the dominant frequency of 2Hz that was close to the fundamental frequency of all basins, and a third wave with the dominant frequency of 4Hz. The waves were applied to a 2Dmodel. The results were compared with those obtained from a 1Dmodel in terms of the timing.
    Then, the basin responses to all three waves (1, 2, and 4 Hz) were subjected to an individual analysis in order to examine the sensitivity of each basin response to its geometrical shape. Results indicated that while the responses of the rectangular and trapezoidal basins were significantly more sensitive to the excitation frequencies, the elliptical and triangular basins showed more stable behaviors to such frequencies. The final stage of the study was dedicated to examine the site 2D effect during the ground motion.
    Results and
    Conclusions
    According to the results of the present study, it could be suggested that the geometrical shape of the sedimentary basin has a significant effect on the responses of the field of seismic waves and that it could result in so different responses from the ones attained after a 1D analysis of the site. In addition, the pattern of the seismic waves’ responses is highly dependent on the geometrical shape and the frequency content of the seismic load. Also, the location where the maximum horizontal acceleration occurs along with the sedimentary basin depends on the excitation wave and varies accordingly. Further, it could be suggested that the site 2D effect results in both considerable amplification and an increase in the length of ground motion.
    The results of the 2D analysis showed remarkable differences with their 1D counterparts: a 1.45 larger response for the rectangular basin, a 1.28 larger response for the trapezoidal basin, a 1.22 larger response for the elliptical basin, and a 1.19 larger response for the triangular basin.
    With the frequency of 1 Hz where the excitation frequency is out of the basin range (i.e. the excitation frequency is below the lowest frequency of basin), the sedimentary basin did not show any signs of amplification and chaos (unlike two other frequencies); instead, it was a cause for de-amplification.
    The frequency of 2 Hz that is subject to resonance resulted in amplifications (absent in 1D analysis) and there are traces of a reduction in the acceleration responses near to the edges of the basins. The proportion of the amplification (in the center of the basins) in 2D to 1D analysis was 1.4 for the rectangular basin, 1.28 for the trapezoidal basin, 1.22 for the elliptical basin, and 1.15 for the triangular basin.
    Keywords: Site Effects, Topographic effects, Sedimentary Basin, Alluvial valley, Amplification, Geotechnical earthquake, Free, Field Motion, Absorbing boundary, Finite Element