فهرست مطالب

Engineering Geology - Volume:11 Issue:4, 2018
  • Volume:11 Issue:4, 2018
  • تاریخ انتشار: 1396/11/30
  • تعداد عناوین: 7
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  • مجتبی بهاالدینی * صفحات 319-342
    یکی از چالش های مهندسان مکانیک سنگ، تغییر خواص مکانیکی سنگ ها با تغییر اندازه نمونه، با عنوان تاثیر مقیاس است. در بحث تاثیر مقیاس بر مقاومت کششی، پژوهش های انجام شده روی سنگ ها بسیار محدود است و غالبا روی بتن انجام گرفته است. نتایج تعدادی از تحقیقات گذشته حاکی از کاهش مقاومت با افزایش قطر است، در حالی که در تعدادی دیگر بی تاثیر بودن مقیاس یا افزایش مقاومت گزارش شده است. هم چنین، اغلب این آزمایش ها روی دامنه کوچکی از قطر انجام شده و رابطه ای کلی که تاثیر مقیاس بر مقاومت کششی سنگ ها را نشان دهد و دارای مقبولیت باشد، وجود ندارد. در این مقاله، تاثیر ابعاد نمونه بر مقاومت کششی برزیلی بررسی می شود. برای این منظور، نمونه های ماسه سنگ با قطر بین 19 تا 145 میلی متر تهیه و آزمایش برزیلی روی این نمونه ها انجام شد. نتایج نشان می دهد که با افزایش قطر نمونه مقاومت کششی کاهش می یابد. در ادامه این بررسی، با استفاده از آنالیز رگرسیون غیرخطی و با استفاده از مدل های هوک و براون، قانون تاثیر مقیاس SEL و قانون مقیاس چند فراکتال MFSL، روابطی برای تخمین مقاومت کششی در قطرهای مختلف ارائه شده و مشخص شد مدل SEL تخمین بهتری از تاثیر مقیاس بر مقاومت کششی ارائه می کند .
    کلیدواژگان: آزمایش برزیلی، تاثیر مقیاس، سنگ بکر، مقاومت کششی، مکانیزم شکست
  • نیما حیدرزاده *، تانیا تسلیمی صفحات 343-362
    در این تحقیق عملکرد رس های معمولی و اصلاح شده در مقاومت فشاری آزاد خاک آلوده به فنل در فن آوری تثبیت و جامدسازی بررسی شد. تمامی نمونه ها شامل2000 میلی گرم بر کیلوگرم فنل بود. از سیمان سفید (15و 30 درصد وزنی) به عنوان جامدکننده و از رس های معمولی و اصلاح شده (8، 15 و 30 درصد وزنی) به عنوان مواد افزودنی با عمر نمونه های 28 روزه استفاده شد. با افزایش مقدار رس ها، مقاومت فشاری آزاد کاهش یافت و این کاهش در نمونه های شامل رس اصلاح شده بیش تر از نمونه های رس معمولی مشاهده شد. مقادیر مقاومت فشاری آزاد تمامی نمونه ها توانست استانداردهای حداقلی تعیین شده برای دفع در محل های بهداشتی از سوی کشورهای فرانسه، هلند، بریتانیا و امریکا را برآورده سازد. نمونه شامل 30 درصد سیمان سفید و 8 درصد بنتونیت، بیش ترین مقدار مقاومت فشاری (4856 کیلوپاسکال) و نمونه شامل 15 درصد سیمان سفید و 30 درصد رس اصلاح شده، کم ترین مقدار مقاومت فشاری آزاد (2226 کیلوپاسکال) را نشان دادند. با توجه به این که قیمت رس اصلاح شده بیش تر از رس معمولی است، اگر در فرآیند تثبیت و جامدسازی خاک آلوده به فنل فقط عامل مقدار مقاومت فشاری مد نظر باشد، استفاده از رس معمولی در مقایسه با رس اصلاح شده مقرون به صرفه تر خواهد بود.
    کلیدواژگان: تثبیت و جامدسازی، مقاومت فشاری آزاد، فنل، رس اصلاح شده
  • مهسا رخ بر *، افشین قشلاقی، گیتی فرقانی صفحات 363-384
    معدن کاری از منابع بالقوه ورود فلزات به داخل محیط به ویژه خاک و گیاهان است. در این پژوهش غلظت و دسترس پذیری فلزات سنگین در خاک ها و گیاهان اطراف سدهای باطله معدن ایرانکوه به عنوان بزرگ ترین معادن سرب و روی کشور بررسی شده است. برای این منظور 31 نمونه خاک از زمین های گلخانه ای اطراف سد باطله فرآوری معدن برداشت شد و غلظت فلزات سنگین، محتوای دسترس پذیر آن ها به همراه برخی خواص فیزیکوشیمیایی خاک اندازه گیری شد. نتایج نشان دهنده غلظت بالای فلزات Zn، Pb و Cd در نمونه های خاک (میانگین به ترتیب 955، 261 و 17/2 میلی گرم بر کیلوگرم) است و با نزدیک شدن به سد باطله بر درجه آلودگی هر سه فلز افزوده می شود. هم چنین این سه فلز با سایر فلزات هم بستگی ضعیفی داشته و از بین خواص خاک نیز با درصد رس هم بستگی معناداری نشان می دهند. برای استخراج فلزات از 17 نمونه خاک منطقه از محلول DTPA استفاده شد. بر اساس نتایج به دست آمده از این روش، سهم غلظت دسترس پذیر از غلظت کل برای فلز Cd از دو فلز دیگر بیش تر است (60 % برای کادمیم، 20 % برای روی و 10 % برای سرب) و با توجه به ماهیت قلیایی نمونه های خاک بخش دسترس پذیر برای هر سه فلز درصد کمی از غلظت کل آن ها را شامل می شود. تعیین غلظت کل فلزات در سبزیجات کشت شده در خاک های گلخانه ای (گیاه ریحان- (Ocimum basilicumنیز نشان داد که غلظت هر سه فلز بررسی شده بسیار بیش تر از غلظت مجاز آن در گیاهان غیرآلوده است و هم بستگی منفی و معناداری بین غلظت فلزات در ریشه و میزان زیست دسترس پذیر آن ها در خاک دیده می شود. که با توجه به نتایج، مصرف این سبزیجات می تواند با ایجاد خطر سلامتی برای مصرف کنندگان در طولانی مدت همراه باشد.
    کلیدواژگان: خاک، فلزات سنگین، زیست دسترس پذیری، سبزیجات، معدن ایرانکوه
  • کاظم صابر چناری *، حسین سلمانی، مریم سادات میرعابدینی صفحات 385-404
    هدف از این پژوهش ارزیابی خطر زمین لغزش حوزه آبخیز زیارت استان گلستان با استفاده از تئوری دمپستر-شفر در سیستم اطلاعات جغرافیایی است. در گام اول با استفاده از گزارشات موجود و تفسیر عکس های هوایی نقشه پراکنش نقاط لغزشی منطقه بررسی شده تهیه شد. از کل نقاط لغزشی (50 نقطه) 35 نقطه آن (70 درصد) برای تهیه نقشه پهنه بندی خطر و نقاط باقی مانده (30 درصد) برای ارزیابی مدل در نظر گرفته شد. در گام دوم 12 عامل موثر بر زمین لغزش برای تهیه نقشه پهنه بندی خطر زمین لغزش در نظر گرفته شد. این عوامل شامل درصد شیب، جهت شیب، ارتفاع، خطوط هم باران، زمین شناسی، کاربری اراضی، بافت خاک، فاصله از جاده، فاصله از گسل، تراکم گسل، فاصله از رودخانه، شاخص قدرت رودخانه هستند. سپس، وزن کلاس های هر عامل مشخص شده و نقشه پهنه بندی خطر زمین لغزش منطقه با 13 روی کرد مدل سازی با استفاده از تئوری دمپستر- شفر تهیه شد. سرانجام برای ارزیابی مدل ها منحنی عملکرد نسبی ترسیم و سطح زیر منحنی محاسبه شد. نتایج ارزیابی نشان داد، تئوری دمپستر-شفر برای روی کرد ششم مدل سازی (حذف عامل لیتولوژی) با سطح زیر منحنی9/92٪ (عالی) و انحراف معیار 045/0، بیش ترین دقت را دارد. از این رو، نقشه خطر زمین لغزش تهیه شده برای منطقه بررسی شده می تواند برای برنامه ریزان و مهندسان در شناسایی مناطق مستعد خطر زمین لغزش و ارائه راهکارهای مناسب برای کاهش و مدیریت خطر مفید باشد.
    کلیدواژگان: خطر زمین لغزش، تئوری دمپستر، شفر، زیارت، گلستان
  • سیدمحمود فاطمی عقدا، حبیب شاه نظری، حمیدرضا کرمی *، مهدی تلخابلو صفحات 405-426
    خاک های کربناته ازلحاظ ویژگی های مقاومتی، خردشدگی دانه ها و نشست خاک، از خاک های مسئله دار در طبیعت هستند که گاهی مشکلاتی را برای مهندسان ژئوتکنیک به وجود می آورند. بخش اعظم این خاک ها در بستر آب های کم عمق مناطق گرمسیری واقع شده است. در ایران نیز در سواحل و جزایر خلیج فارس و دریای عمان لایه های نسبتا ضخیمی از رسوبات کربناته موجود است. با توجه به اهمیت و گستردگی پروژه هایی بزرگی نظیر ساخت پل بزرگ خلیج فارس مابین بندرعباس و جزیره قشم، مخازن ذخیره نفت و گاز، سکوهای استخراج نفت و ساخت اسکله ها که اخیرا در این مناطق در دست اجرا هستند، شناخت و بررسی چنین خاک هایی اهمیت فراوانی دارد. در این تحقیق به بررسی تاثیر بافت رسوبات کربناته بر خردشدگی دانه ها می پردازیم. نتایج تحقیق نشان می دهد افزایش اندازه موثر دانه ها و ضریب شکل آن ها به صورت توانی با خردشدگی آن ها ارتباط داشته و با افزایش هم زمان دو پارامتر فوق میزان خردشدگی تشدید می شود.
    کلیدواژگان: خاک های کربناته، خردشدگی، ضریب شکل، اندازه موثر سنگ دانه
  • مجید مهدی، هوشنگ کاتبی صفحات 427-454
    تسلیح خاک به وسیله ژئوسنتتیک ها روشی موثر برای افزایش مقاومت برخاس] سازه های مدفون است. در این مقاله از المان مسلح کننده جدیدی که شامل تعدادی صفحات مهاری است و به ژئوگرید متصل می شود و موجب افزایش مقاومت بیرون کشیدگی ژئوگرید می شود استفاده شده است که به آن سیستم مهار- شبکه گفته می شود. بررسی عددی سه بعدی با استفاده از نرم افزار تفاضل محدود FLAC-3D برای بررسی مقاومت برخاست خطوط لوله مدفون در ماسه مسلح شده با این سیستم جدید انجام شده است. نتایج نشان می دهند که به علت گسترده تر شدن سطح گسیختگی خاک، استفاده از این سیستم مهار-شبکه در توده خاک، مقاومت برخاست خطوط لوله مدفون را به طور چشم گیری افزایش می دهد. طوری که جهت لوله با قطر خارجی 50 میلی متر، استفاده از سیستم مسلح کننده مهار- شبکه موجب افزایش مقاومت برخاست لوله به میزان 3/2 برابر حالت استفاده از ژئوگرید و 7/3 برابر حالت بدون مسلح کننده می شود. در مقایسه با چند لایه مسلح کننده، بازدهی استفاده از یک لایه مسلح کننده بیش تر است. هم چنین بازدهی لایه مسلح کننده در خاک های سست بیش تر از خاک های متراکم است. به علاوه، با افزایش قطر لوله، تاثیر لایه مسلح کننده کم تر خواهد بود.
    کلیدواژگان: مقاومت برخاست، خطوط لوله مدفون، مدل سازی عددی، خاک مسلح، ژئوگرید، مهار، شبکه
  • علیرضا نجیبی، محمد غفوری *، غلامرضا لشکری پور، محمدرضا آصف صفحات 455-470
    تعیین جهت و مقدار تنش های برجا پیش نیاز اساسی در حفر چاه های نفت و انجام عملیات توسعه میادین نظیر شکافت هیدرولیکی محسوب می شود. تحلیل شکستگی های برشی یکی از روش های تعیین جهت و مقدار تنش های برجا است. شکستگی های برشی به دلیل اعمال فشار گل حفاری کم تر از مقدار بهینه، به موازات جهت تنش برجای افقی حداقل (Sh) در دیواره چاه گسترش می یابند. در این پژوهش، جهت و مقدار این تنش ها در یکی از چاه های نفت منطقه اهواز به روش تحلیل شکستگی های برشی اندازه گیری شده است. بر این اساس، جهت تنش برجای افقی حداکثر (SH) در امتداد E35N و جهت Sh نیز در راستای W55N قرار دارد. بزرگای تنش برجای قائم (SV) کم تر از مقدار SH و بیش تر از مقادیر Sh است که بیان گر وجود رژیم تکتونیک امتدادلغز در منطقه است. تعیین جهت و مقدار این تنش ها امکان تخمین فشار بهینه گل حفاری و انتخاب مسیر مناسب حفاری در حفر چاه های انحرافی را فراهم می کند.
    کلیدواژگان: تنش های برجا، شکستگی های برشی چاه، ژئومکانیک، شکستگی، اهواز
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  • Mojtaba Bahaaddini * Pages 319-342
    Determination of the mechanical properties of rock materials has been remained as a challenge for engineering geologists. In-situ tests are rarely used to determine the mechanical properties of rocks due to difficulties in sample preparation, performing and interpretation of the results, high costs as well as the required long time for doing the experiments. The common approach to determine the mechanical properties of rock materials is through conducting laboratory experiments and estimation the in-situ properties based on these laboratory results. This approximation, which is called scale effect, has been remained as a challenge for engineering geologists and practical rock engineers for decades.
    Keywords: model can provide a better estimation of tensile strength at different diameters
  • Nima Headarzadeh *, Tania Taslimi Pages 343-362
    Introduction
    One of the most important 1-ring aromatic organic pollutants is phenol and its related compounds. These compounds are classified as hazardous wastes base on U.S.EPA primary contaminates list. The phenolic compounds are very poisonous and these are harmful for human health and also for other biota.
    To control the movement of such hazardous organic waste in a contaminated soil, solidification/stabilization (S/S) process can be an effective alternative. Due to the negative impact of organic compounds on the cement hydration, the cement-based S/S may be not effective for controlling the movement of such pollutants. To avoid these effects, using some additives during solidification period has been recommended. One of the proposed of such compounds is organophilic clay that is the modified montmorillonite by quaternary ammonium salts (QAS). There are several researches to evaluate the organophilic clay effect on adsorption and stabilization of organic compounds during S/S process. The effectivity of S/S process can be examined by several tests such as leaching test, durability, unconfined compressive strength (UCS), etc.
    In this study, efficiency of ordinary and organophilic clay was evaluated in the solidification and stabilization process based on unconfined compressive strength of a phenol-contaminated soil.
    Material and
    Methods
    In this study, an artificially phenol contaminated sand was considered to evaluate the effectivity of the white cement based S/S process by using two different additives of ordinary and organophilic clay.
    The contaminated sand contains 2000 ppm of phenol. S/S process was conducted on 14 samples with different amounts of white cement (15 and 30 wt%) as binder and ordinary/organophilic clay (0, 8, 15, and 30 wt % for each of them) as the additives. Two zero percent additive samples are considered as control samples.
    All samples were cured for 28 days and then UCS test was conducted for all of them.
    Results And Discussion
    Unconfined compressive strength of all examined samples were ranged from 2226 to 6999 KPa. In the samples with equal amount of cement, th higher UCS values can be observed in blank samples (without any additives and phenol). By adding phenol in the examined sand, UCS of the solidified sample reduces 3 -3.5%.Moreover, results showed that UCS was reduced by increasing the amount of clays. The reduction of the samples containing organophilic clay was higher than samples containing ordinary clay. Unconfined compressive strength values of all samples met the minimum standards indicated by France, Netherlands, Britain and America for disposal in a sanitary landfill. The sample with 30% white cement and 8% bentonite was the maximum amount of UCS (4856 KPa) and the sample with 15% white cement and 30% organophilic clay was the minimum one (2226 KPa). In this study, the average cost of organophilic clay-based solidified samples was 2.3 to 2.8 times more than the average cost of the bentonite-based solidified samples.
    Conclusion
    In this study, the strength of the cement-based solidified samples contaminated by phenol was investigated. The summary of the findings of the research is as follows: 1. By adding the phenol to pure sand, the UCS of the samples can be reduced 3-3.5 %.
    2. Addition of organophilic clay reduces the UCS of the samples more than the ordinary clay (bentonite) in the same amount.
    3. All samples met the recommended UCS level for the S/S process. The minimum UCS level is for the sample with 15% of cement and 30% of organophilic clay.
    The cost of S/S process is between 23 and 650 $/ton of contaminated soil depending on the amount of used additives and binder. The samples containing organophilic clay has a higher cost than the similar sample containing ordinary clay.
    4. To evaluate the S/S process effectivity, a leaching test of phenol (such as TCLP) is recommended.
    Keywords: Solidification, stabilization, Unconfined compressive strength, Phenol, Organophilic clay
  • Mahsa Rokhbar *, Afshin Qishlaqi, Giti Forghani Pages 363-384
    Introduction
    Exploitation or processing of ores is usually associated with the production of a large amount of waste materials. These materials often have a high concentration of metals which can enter the environment through weathering or erosion. It is well-known that the measurement of the total concentration of metals cannot be an adequate for evaluating the pollution status of soil. Therefore, in most studies on soil contamination, bioavailability content of metals is determined by which can predicate the fate of the metals entering into the other parts of the environment such as plants, water or human food chain. The bioavailability of metals in the soil environment is the exchangeable and absorbable metals for plants, which depends on their exchangeability and absorption by soil organisms especially plants. This is also the function of the chemical form of each element in the soil. The main purpose of the present study was to measure the total concentrations along with the bioavailable content of metals in soils and plants around the Irankuh mine tailing dams.
    Area of study: The Irankuh lead and zinc mine is located 20 kilometers southwest of Isfahan. This mine is of MVT type Pb-Zn deposit which occurred mainly in limestone and dolostone of lower cretaceous age. The Irankuh mine is an open-pit mine with annual extraction of 358 thousand of PbO and ZnO. The exploitation of mine is also associated with the production of a large amount of waste material which is piled in open dumps around the mine. The main minerals of ores are galena, sphalerite and pyrite.
    Materials And Methods
    31 sampling sites were selected randomly for collecting agricultural soils around the tailing dams. Each soil sample is actually composite sample of four samples which are taken from a depth of 15 to 20 cm. Seven cultivated plants (Ocimum basilicum) were sampled from green houses in the vicinity of tailing dams. After drying and sieving, about 50g of the soils are chemically analyzed in order to determine the total concentration of the metals by the ICP-OES method. Plant samples after drying were changed to ash in the furnace at temperature > 500 C. The concentrations of metals (Zn, Pb and Cd) were then measured by Atomic Absorption Spectrometers in their stem, roots and leaves.
    pH samples of soil were also determined using the EPA 9045 method. Walkley and Black method were used to measure the amount of organic matter. The cation exchange capacity (CEC) of soil samples was also determined based on EPA 9087 method. Soil texture determined using hydrometric method and then classified according to USDA classification. Diethylene Triamine Pentaacetic Acid (DTPA) extractable metals (bioavailable content) were determined using the method by Lindsay and Norvell (1978) and their concentrations in the DTPA extracts were determined by Atomic Absorption Spectrophotometer (AAS).
    The metal transfer from soil to plant was calculated using the transfer factor (TF: metal content in plant divided by metal content in soil).
    Results And Discussion
    The soil pH of the studied samples varies from 7.36 to 8.35. Cation exchange capacity (CEC) of soil samples was estimated to be in the range of 4 to 22.2 Meq/100 g. Also, the amount of organic matter in the studied soil samples varies from 0.17 to 3.43%. The relative high levels of soil organic matter are probably due to addition of organic manure to soil through agricultural activity. The total concentration of these three matls are significantly higher than their corresponding values in the crust implying that the mining activity and tailing dams greatly elevated the concentration of these metals in soils. Statistically, there is a significant positive correlation among Zn, Pb and Cd (at confidence level of 0.01) indicating that their potential source is the same or having similar geochemical behavior in the soil. The soil clay content showed a significant correlation at the level of 0.05 with Zn, Cd and Pb. This indicates that clay fraction plays a significant role in absorption of these metals in soil. According to the results of single extraction (DTPA method), the proportion of available content for Cd is higher than that of Zn and Pb. Cadmium is often characterized by its high mobility in soil media. Based on the correlation coefficients at the confidence level of 0.01, it is also observed that the increase in total concentration of Cd increased its bioavailability content in the soil consequently increase the availability of other elements in the soil. Therefore, it can be inferred that the availability of Cd in the soils of the study area is likely to be increased in the presence of Zn and Pb because in sites where the total concentration of Pb and Zn is high, the content of Cd availability has also elevated.
    Based on the comparison of the average concentration of the metals in different parts of the plants, the concentration of metals is ordered as follows stem> leaf> root, which indicates the high root capacity for the accumulation of metals. The average transfer factor (TF) for Cd is obtained much higher than those of Zn and Pb. There is also a negative significantly correlation between the concentrations of Cd in the aerial parts of the plants and its bioavailability concentration in the soil. Also, there is positive and significant correlation between Zn and Cd for all three different parts and its bioavailability concentration in the soil. In the case of Pb, a significant correlation is observed between stem and root parts. This means that Cd and Zn after being absorbed by the root, are more likely being uptake by the plants due to high mobility of zinc. However due to less mobility of Pb, it is seemingly entered into the plant aerial parts after absorption by the root.
    Conclusion
    The concentration and degree of contamination of the studied soils is very high in terms of total Pb, Zn and Cd concentrations in agricultural soils around the Irankuh mine. The increased heavy metal contents in soils can be attributed to mining activity and tailing dams near cultivated lands. The measurement of the bioavailable content of these metals indicates that the Cd has the highest availability as compared to Zn and Pb. The average concentration of Pb and Cd in different parts of plant which is higher than the permissible limits, implying that the transfer of the available metal part (especially Cd) from the contaminated soil into the plant. Based on the calculated health risk assessment index in this study, it can generally be concluded that the gradual accumulation of these metals, especially in aerial parts of basil might have health hazards for local consumers.
    Keywords: Soil, Heavy metals, Bioavailability, Vegetables, Irankuh mine
  • Kazem Saber Chenari *, Hossein Salmani, Maryam Sadat Mirabedini Pages 385-404
    Introduction
    Landslides are natural events that one or more factors can effect in its occurrence that each of them plays a special role in this field. The hazard assessments of this phenomenon are a complicated problem due to the interference of the effective factors in its occurrence. The uncertainty that is due to ambiguous conditions of geology characteristics, hydrology, tectonics, land cover, rain, erosion, temperature fluctuations in the slope instability demonstrate the benefit of accurate methods in the study of slope instability. Since the prediction of the landslide occurrence is out of the power of current knowledge, identifying sensitive areas to landslide and ranking it can protect us from landslide dangers. According to preliminary estimates, annually 140 million dollar financial damages inflict by landslides over the country, while the loss of unrecoverable natural resources is not counted. In general, the ultimate goal of studying landslides can be found the ways that to reduce damages caused by them. Therefore, it is necessary to prepare the landslide hazard map.
    The main goal of this research is landslide hazard zonation of Ziarat watershed using Dempster-Shafer. For this purpose, 13 modeling approach (using all factors and eliminating of individual factors) to prepare the hazard maps have used. Ultimately, the accuracy of the model has been evaluated using receiver operating characteristic (ROC) curves. The study area is one of the most prone areas to the landslide in the Golestan region. Sensitive lithology units, high diversity of topography and land-use changes have increased landslide susceptibility in this area. Therefore, investigation of effective factors in landslide occurrence and providing zonation maps to take management action in this area is necessary.
    Material and
    Methods
    The study area is located in northern Iran, Golestan province. The Ziyarat watershed with an area of about 7800 hectares lies between longitudes 54º 10ʹ 13ʺE and 54º 23ʹ 55ʺE, and latitudes of 36º 36ʹ 58ʺN and 36º 46ʹ 11ʺN. At first, extensive field observations of the study area and aerial photos in 1:25000 scales have been used. So, a total of 50 sliding points are recognized and inventory map is produced (dependent variables). Then, 70% of total points (35 points) have considered for hazard zonation maps and 30% (15 points) for model validation.
    In this research, twelve factors affecting (independent variables) landslide occurrence to provide hazard maps were applied. These factors include land-use, soil texture, geology, rainfall, slope, aspect, altitude, distance from faults, roads and rivers, stream power index (SPI) and plan curvature (CP). These factors can be divided into three broad categories which are topographical, geological and environmental conditioning parameters. The maps of these 12 factors have been produced using basis maps (DEM and Geology maps) in GIS software. The amount of Landslide density in each factor class have calculated from a combination of independent and dependent variables, and rating of classes have done based on Dempster-Shafer equations. Finally, the Landslide hazard zoning map has drawn from the summation of weighting maps in Arc GIS with 13 approaches. In this map, Value of each pixel is calculated by summing weight of all factors in that pixel. The pixel values are categorized based on natural breaks classifier into very low, low, medium, high and very high hazard zones. Then, an accuracy of zoning map has been evaluated by ROC.
    Results And Discussion
    The result of effecting factors on landslide classification shows that Mobarak formation, forest and agriculture land use, areas with low distance from road and rivers, low altitudes, rainfall buffer of 550-650 mm, northwest aspect, clay-loam soil texture, areas with high stream power index, high slope amplitude and area with fault density lower than 2 km/km2 contain the most susceptibility to landslide. The result of model validation using ROC demonstrates that with eliminating lithology factor Dempster-Shafer model with 92.9% accuracy is located in the great class. Also, the model accuracy shows that with eliminating rain and altitude factors the model accuracy is decreased to 73.8% and 80.4%, respectively. So, these two factors were identified as the most effective factors in the occurrence of the landslide in the studied area. Based on the landslide zoning hazard map of the Ziarat watershed and landslide points (15 points) that are considered for model validation the 20, 40, 26.67, 13.33 and zero percent of landslides is situated in the very high, high, moderate, low and very low hazard classes.
    Conclusion
    In this research, susceptible areas to landslide in the Ziarat watershed have been mapped with the Dempster-Shafer model. For this purpose, 13 modeling approach to prepare the hazard maps have been used. The following conclusions are obtained from this study.
    - The rain and altitude factors were identified as the most effective factors in the occurrence of landslide in the Ziarat watershed.
    - Based on the landslide zoning hazard map of the Ziarat watershed 60 percent of landslides is situated in the very high to high hazard classes.
    - The produced landslide hazard map is useful for planners and engineers to reorganize the areas which are susceptible for landslide hazard, and offer appropriate methods for hazard reduction and management.
    Keywords: Landslide Hazard, Dempster, Shafer model, Ziarat, Golestan
  • Seyyd Mahmod Fatemi Aghda, Habib Shahnazari, Hamidreza Karami *, Mehdi Talkhablou Pages 405-426
    Carbonate soils are different from silicate soils respect to their origination and engineering behavior. Particles of these soils are mainly residual or debris of sea animals or plants with large amount of calcium carbonate. They also may be chemical sedimentation of calcium carbonate over other soil particles in specific region of seas and oceans. The most important characteristic of these soils is the crushability of their aggregates under loading which is mainly due their shape and also small voids inside of them. Crushability and subsequent volume changes in carbonate soils have caused many engineering problems in some geotechnical structures such as.
    Keywords: Carbonate soils, Sand, Crushing, Effective size, Shape index
  • Majid Mahdi, Hooshang Katebi Pages 427-454
    Recently, several studies on buried pipelines have been conducted to determine their uplift behavior as a function of burial depth, type of soil, and degree of compaction, using mathematical, numerical and experimental modeling.
    One of the geosynthetics applications is the construction of a reinforced soil foundation to increase the bearing capacity of shallow spread footings. Recently, a new reinforcement element to improve the bearing capacity of soils has been introduced and numerically studied by Hatef et al. The main idea behind the new system is adding anchors to ordinary geogrid. This system has been named as Grid-Anchor (it is not a trade name yet). In this system, a foundation that is supported by the soil reinforced with Grid-Anchor is used; the anchors are made from 10×10×10 mm cubic elements. The obtained results indicate that the Grid-Anchor system of reinforcing can increase the bearing capacity 2.74 times greater than that for ordinary geogrid and 4.43 times greater than for non-reinforced sand.
    Keywords: Uplift Resistance, Buried Pipelines, Numerical Modeling, Reinforced Sand, Geogrid, Grid, Anchor
  • Ali Reza Najibi, Mohammad Ghafoori *, Gholam Reza Lashkaripour, Mohammad Reza Asef Pages 455-470
    Determination of in situ stress-direction and magnitude are prerequisite for any oil well drilling and oil field development such as hydraulic fracturing. One of the simplest and most widely used methods is called borehole breakout analysis. Breakouts are compression fractures made in the direction of minimum horizontal in situ stress (Sh), if drilling mud pressure be lower than optimum mud pressure. Some borehole imaging logs such as FMI, FMS and UBI are appropriate tools for wellbore fracture detection. These fractures are distinguished in the logs as dark and symmetrical points (or lines) on both sides of the well and are used as an indicator for in situ stress studies. The size and shape of these fractures are strongly depend on the magnitude of the in situ stress. Therefore, many researchers suggested that by analyzing the geometric shape of the borehole breakout is an appropriate technique for estimation of in situ stress components.
    Keywords: In situ stress, Borehole Breakout, Geomechanics, Fracture, Ahwaz