بررسی خصوصیات زمین‌شناسی مهندسی پریدوتیت‌ها(مطالعۀ موردی: شهرستان هرسین، استان کرمانشاه)

بخش اعظم شرق و جنوب شرق استان کرمانشاه از رخنمون پریدوتیت‌ها تشکیل‌شده است. شناخت ویژگی‌های زمین‌شناسی مهندسی پریدوتیت‌های هرسین به شناخت عمومی زمین‌شناسی مهندسی محل کمک زیادی می‌کند. هدف این مقاله بررسی و معرفی خصوصیات زمین‌شناسی مهندسی پریدوتیت‌های هرسین در استان کرمانشاه است. در این پژوهش، به‌منظور شناخت خصوصیات و رفتار مهندسی این سنگ‌ها، 15 بلوک از پریدوتیت‌های هرسین انتخاب شد و برای انجام آزمایش‌های آزمایشگاهی به آزمایشگاه انتقال داده شد. خصوصیات سنگ‌‌شناسی، ویژگی‌های فیزیکی و مکانیکی پریدوتیت‌ها تعیین ‌شده است. نمونه‌ها تحت آزمایش‌های سختی چکش ‌اشمیت، دوام وارفتگی، شاخص بار نقطه‌ای، مقاومت فشاری تک‌محوری، مقاومت کشش برزیلی و سرعت موج قرار گرفته‌اند. نتایج این تحقیق نشان داد که تفاوت در خصوصیات سنگ‌شناسی و فیزیکی منجر به تغییر در خصوصیات مکانیکی آن‌ها شده است. با استفاده از آنالیزهای رگرسیون نرم‌افزار excell، ارتباط بین خصوصیات فیزیکی و مکانیکی پریدوتیت‌ها تعیین شد. بر اساس نتایج به‌دست ‌آمده، میزان انطباق بیش‌تری بین نتایج خصوصیات مکانیکی در حالت خشک نسبت به اشباع وجود دارد. بیش‌ترین انطباق بین آزمایش مقاومت کششی برزیلی(bts) با سختی ‌اشمیت (shv) در حالت خشک است که میزان ضریب تعیین(r2) برابر 0/95 است

The study of engineering geological properties of peridotites in Harsin, Kermanshah province (A case study)

Because of the diversity in petrography, peridotites have variable physical and mechanical properties. For this reason, knowledge of resistance properties and their deformation will help with the prediction of engineering behavior of these rocks. Due to the large spread of igneous rocks, especially peridotite, in Zagros, northeastern and central Iran, special attention has been paid to their petrographic, physical and mechanical characteristics. The construction of the structure within or on the peridotites and the choice for the purpose of the stone borrow depends on the recognition of its engineering geology characteristics. In this paper, in addition to the field and laboratory study, the geological characteristics of peridotite engineering has been investigated. Material and methods In order to study the geological characteristics of the peridotites of Harsin region, 15 suitable blocks were selected and transferred to the laboratory. Accordingly, from collected rock samples, 150 cylindrical cores of diameter 54 mm were prepared and physical and mechanical tests were performed according to (ISRM, 2007) and (ASTM, 2001) guidelines. In this research, after sampling of the study area and preparing the core for the lithological characteristics of the samples by providing thin sections of them with polarizing microscopy was studied.Results and discussionBy considering the results of laboratory tests and analysis from Harsin peridotites in Kermanshah province, we can acclaim that with increasing the percentage of minerals in olivine and pyroxene in rock, the strength was decreased and the levels weaknesses, which is due to the weak structure of the mineralolivine and pyroxene. According to the physical properties test and Anon classification, the porosity percentage in porosity percentage is low and as a result the amount of water absorption index is low. Based on the Gamble classification, all peridotites are very resistant to durability and based on the Franklin and Chandra classification, all samples are extremely resistant. The results of this study showed that the single axial compressive strength, elasticity modulus, point load index and tensile strength were decreased with an increase in humidity content of peridotite samples. This is due to the fact that with the increase of humidity pore pressure of water increases. According to the Anon classification, the peridotites are very high in terms of the length of the longitudinal passage through the rock. The highest compliance between the Brazilian Tensile strength test (BTS) and Schmidt hammer (SHV) was achieved in the dry condition and the determination coefficient (R2) equals to 0.95 was obtained. Also there is an acceptable relation between the Brazilian Tensile Strength Test (BTS) and the dry volume unit weight ( gamma;d) with the determination coefficient (R2) of 0.93. In addition, there is an admissible relationship between durability test and singleaxial compressive strength, with a coefficient determination (R2) of 0.94. Regarding the obtained regressions in this study, the physical and mechanical properties show good agreement and most of the equations have an acceptable coefficient determination.