بررسی تأثیر زبری سطح ناپیوستگی بر مقاومت نمونه‌های سنگی درزه‌دار

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه مهندسی مکانیک سنگ، دانشگاه تربیت مدرس

2 1. گروه مهندسی مکانیک سنگ، دانشگاه تربیت مدرس

3 گروه مهندسی مکانیک سنگ، دانشگاه بین‌المللی امام خمینی قزوین

چکیده

ناپیوستگی­ها یکی از مهمترین عواملی هستند که باعث ایجاد آنیزوتروپی مکانیکی در سنگ شده و سبب کاهش مقاومت سنگ می­گردند، در نتیجه جهت توصیف رفتار سنگ باید خواص مربوط به ناپیوستگی­ها و میزان تاثیری که بر روی مقاومت سنگ می­گذارند مورد توجه و بررسی قرار گیرد. از جمله مهمترین خواص ناپیوستگی­ها که بر روی مقاومت نمونه­ی انیزوتروپ اثر می­گذارد، زبری سطح ناپیوستگی­هاست. از طرفی با توجه به اینکه در طبیعت سنگ­ها تحت فشار جانبی قرار دارند، بنابراین بهتر است رفتار سنگ­های درزه­دار تحت شرایط محصور شده مورد بررسی قرار بگیرد. در تحقیق حاضر به منظور بررسی تأثیر زبری سطح درزه بر روی مقاومت سنگ، از نمونه­های مصنوعی ساخته شده از ترکیب گچ و سیمان استفاده شده است. نمونه­های مصنوعی در چهار سطح زبری و در هفت زاویه­ی شیب ناپیوستگی نسبت به تنش اصلی حداکثر تهیه شدند، و در پنج فشار جانبی 5/0، 5/1، 2، 5/3 و 5 مگاپاسکال تحت آزمایش مقاومت فشاری سه محوری قرار گرفتند. نتایج حاصل از این تحقیق نشان داد با افزایش زبری سطح ناپیوستگی، مقاومت سنگ­های انیزوتروپ افزایش می­یابد، که این افزایش مقاومت هنگامی که زاویه­ی ناپیوستگی با تنش اصلی حداکثر بین ˚25 تا ˚50 باشد بیشتر از بخش­های دیگر است. همچنین نتایج نشان داد که بیشترین مقاومت سنگ انیزوتروپ در یکی از زوایای 0 و یا 90 درجه اتفاق می­افتد که این زاویه برای مقادیر مختلف JRC متفاوت است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of discontinuity surface roughness on the strength of jointed rock samples

نویسندگان [English]

  • Abolfazl Rezaeipoor 1
  • Hamidreza Nejati 2
  • Abdolhadi Ghazvinian 1
  • Mir raoof Hadei 3
1   Rock Mechanics Division, Tarbiat Modares University, Tehran, Iran, h.nejati@modares.ac.ir
2    Rock Mechanics Division, Tarbiat Modares University, Tehran, Iran, h.nejati@modares.ac.ir
3 Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

It is seldom possible that rock engineering structures found without joints, cracks, or discontinuities. Discontinuities are one of the most important phenomena that cause the mechanical anisotropy in rocks. This mechanical anisotropy would impose reduction of strength. Therefore the discontinuities and degree of their influence on the rocks must be studied carefully in order to define the behavior of rocks. The confining pressure, on the other hand, is an important parameter that controls the percentage effect of the rock discontinuities on the rock strength. The purpose of this study is evaluation of the effect of discontinuity surface roughness on strength of jointed rock samples at different confining pressures. For this purpose, an intensive laboratory investigation was undertaken to test jointed specimen at various discontinuity angles (β=0, 15, 30, 45, 60, 75 and 90 degrees) and confining pressures (0.5, 1.5, 2, 3.5 and 5 MPa). The rock discontinuities possess various roughness that were controlled by joint roughness coefficient (JRC=0, 7, 12 and 17). Fabricated artificial samples which included a rough discontinuity were prepared by Cement and Plaster of Paris. These specimens were used for simulation of mechanical anisotropy subjected to uniaxial and triaxial tests based on the ISRM suggested methods. The results of experimental tests indicated that, with an increase in discontinuity surface roughness and lateral pressure, the strength of the anisotropic samples increases. Also it is shown that the orientation of discontinuity influence on the strength of specimens and the maximum strength achieved at the specimen with β=25 to 50 degrees.

کلیدواژه‌ها [English]

  • Anisotropy
  • Discontinuity Surface Roughness
  • Confining Pressure
  • Jointed Rocks
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