تأثیر میزان تنش و ابعاد صفحه بر مدول تغییر شکل توده سنگ در آزمایش بارگذاری صفحه‌ای

نوع مقاله : یادداشت فنی

نویسندگان

1 گروه زمین شناسی، دانشکده علوم، دانشگاه فردوسی مشهد

2 گروه زمین شناسی، دانشکده علوم، دانشگاه اصفهان

10.29252/anm.8.16.95

چکیده

مدول تغییر شکل توده‌سنگ که از مهم‌ترین پارامترهای توده‌سنگ در طراحی‌های مهندسی سنگ است، به دو روش مستقیم(با استفاده از روابط تجربی) و غیر مستقیم(با استفاده از آزمایش‌های برجا) به دست می‌آید. آزمایش بارگذاری صفحه‌ای با توجه به حجم نسبتاً بزرگی از سنگ، که تحت تأثیر قرار می‌دهد و نیز روش انجام ساده‌تر آن، از معمول‌ترین آزمایش‌ها برای اندازه‌گیری مدول تغییرشکل‌پذیری برجای توده‌سنگ است. این آزمایش‌ها بسته به هدف آزمایش و کاربرد نتایج آن، با تنش‌های متفاوت و اندازه صفحات بارگذاری متفاوت انجام می‌شوند. در این پژوهش، مقایسه‌ای بین نتایج آزمایش‌های انجام شده با دو تنش مختلف و همچنین صفحات با قطر متفاوت صورت گرفته است. در این مقایسه از روش‌های آماری تحلیل همبستگی و آزمون t با زوج داده‌ها استفاده گردید. نتایج تحلیل‌های انجام شده بر روی آزمایش‌های با حداکثر تنش‌های 20 و 40 مگاپاسکال، نشان می‌دهد که بین نتایج آزمایش با بارهای مختلف، اختلاف معنی‌داری وجود ندارد و میزان بیشینه تنش وارده بر سنگ، بر مدول تغییرشکل‌پذیری به دست آمده از آزمایش، تأثیری نداشته است ولی نتایج حاصل از آزمایش‌هایی که با دو صفحه با قطرهای متفاوت در یک موقعیت انجام شده‌اند، نشان می‌دهد که، اختلاف معنی‌داری بین آنها وجود دارد و مدول‌ تغییر شکل‌پذیری به دست آمده از آزمایش با صفحات با قطر بزرگ‌تر، در توده‌سنگ‌های با کیفیت بالا، بزرگ‌تر از صفحات با قطر کم‌تر بوده و در توده‌سنگ‌های ضعیف، برعکس است. به نظر می‌رسد، این اختلاف ناشی از تأثیر نسبت ابعاد صفحه بارگذاری به ابعاد گالری آزمایش باشد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Effects of Stress Value and Loading Plate Dimensions on In-situ Deformation Modulus of Rock Mass in Plate Loading Test

نویسندگان [English]

  • Mohsen Rezaei 1
  • Mohammad Ghafoori 1
  • Rasoul Ajalloeian 2
1 Geology Group, Dept. of Sciences, Ferdowsi University of Mashhad
2 Geology Group, Dept. of Sciences, University of Isfahan
چکیده [English]

Summary
The plate loading test is one of the most common in-situ tests used for evaluation of rock mass deformation modulus. In this test, during several cycles of loading and unloading, corresponding displacements are measured. These tests are carried out under different values of stress and by different plate dimensions. In this study, a comparison has been made between the results of this test considering two different stress values and two different plate sizes.
 
Introduction
Rock mass deformation modulus (Erm) is a basic input parameter for most rock engineering projects. For these purposes, it is necessary to obtain this parameter before starting numerical modeling. The plate loading test is a common test for determination of rock mass deformation modulus. This test has been used in several projects around the world. Erm of rock masses in Bakhtiari dam site is determined by Plate loading tests using different loading plate sizes and different stress values. Bakhtiari dam site is located in southwest part of Iran, almost 70 km northeast of Andimeshk city (Khuzestan province), and 65 km southwest of Doroud city (Lorestan province). In this paper, the obtained Erm from plate loading tests with different stress values and different plate sizes has been compared.
 
Methodology and Approaches
Plate loading tests at Bakhtiari Dam site are carried out using rigid loading plates with diameters of 650 and 915 mm and under maximum stresses equal to 20 and 40 MPa. In this test, two opposite areas in test galleries are loaded using rigid loading plates by means of hydraulic pump system. During the tests, the rock displacements are measured using borehole extensometers that fixed in several positions inside the drilled boreholes in the center of each loading area. The deeper extensometer in each borehole (used as a fixed point) is positioned at the end of borehole at depths more than 6 m. Erm is calculated according to ASTM D 4394 – 08.
 
Results and Conclusions
In the Bakhtiari dam site, plate loading tests carried out to determine deformation modulus of rock mass with different loading plate size and different stresses. In case of two maximum stress values of 20 and 40 MPa, no significant difference is evaluated. Conversely, using two different diameter plates in same position resulted in significant different results. For high quality rock masses, the larger the plate diameter is, the greater the evaluated Erm is. This difference is recognized to be related to the ratio of gallery dimension to loading plate size.

کلیدواژه‌ها [English]

  • Rock Mass
  • Plate Loading Test
  • Stress
  • In Situ Test
  • Deformation Modulus

مراجع

[1]           Palmstrom, A. and R. Singh, (2001), "The deformation modulus of rock masses - comparisons between in situ tests and indirect estimates", Tunnelling and Underground Space Technology, 16(3), 115-131.
[2]           Sonmez, H., Gokceoglu, C., Nefeslioglu, H. A., & Kayabasi, A., (2006), "Estimation of rock modulus: For intact rocks with an artificial neural network and for rock masses with a new empirical equation", International Journal of Rock Mechanics and Mining Sciences, 43, 224-235.
[3]           Hoek, E. and M. S. Diederichs, (2006), "Empirical estimation of rock mass modulus", International Journal of Rock Mechanics and Mining Sciences, 43, 203-215.
[4]           Barton, N., (2002), "Some new Q-value correlations to assist in site characterisation and tunnel design", International Journal of Rock Mechanics and Mining Sciences, 39, 185-216.
[5]           Palmstrom, A., (1996), "Characterizing rock masses by RMi for use in practical rock engineering(Part1: the development of the rock mass index(RMi))", Tunnelling and Underground Space Technology, 11(2), 175-188.
[6]           Deere, D. U. (1989). "Rock quality designation(RQD) after twenty years ", U.S. Army crops of engineering: 67.
[7]           Gokceoglu, C., Sonmez, H., & Kayabasi, A., (2003), "Predicting the deformation moduli of rock masses", International Journal of Rock Mechanics and Mining Sciences, 40, 701-710.
[8]           Zhang, L. and H. H. Einstein,(2004), "Using RQD to estimate the deformation modulus of rock masses", International Journal of Rock Mechanics and Mining Sciences, 41, 337-341.
[9]           Kayabasi, A., Kayabasi, A., Gokceoglu, C., & Ercanoglu, M., (2003), "Estimating the deformation modulus of rock masses: a comparative study", International Journal of Rock Mechanics and Mining Sciences, 40, 55-63.
[10]         Hoek, E., Carranza-Torres, C., & Corkum, B., (2002), "Hoek- Brown failure criterion- 2002 edition", North American Rock Mechanicss Society Meeting, Torento, Canada.
[11]         Nejati, H. R., Ghazvinian, A., Moosavi, S. A., & Sarfarazi, V., (2014), "On the use of the RMR system for estimation of rock mass deformation modulus", Bulletin of Engineering Geology and Environment, 73(2), 531-540.
[12]         Palmstrom, A. (1995). "RMi - a rock mass characterization system for rock engineering purposes", Oslo, University of Oslo, Ph.D: 381.
[13]         Sonmez, H., Gokceoglu, C., & Ulusay, R., (2004), "Indirect determination of the modulus of deformation of rock masses based on the GSI system", International Journal of Rock Mechanics and Mining Sciences, 41, 849–857.
[14]         Carvalho, J.,(2004), "Estimation of rock mass modulus", Personal comminucation.
[15]         Shen, J., Karakus, M., & Xu, C., (2012), "A comparative study for empirical equations in estimating deformation modulus of rock masses", Tunnelling and Underground Space Technology, 32, 245-250.
[16]         Lowson, A. R. and Z. T. Bieniawski (2013). "Critical Assessment of RMR based Tunnel Design Practices: a Practical Engineer’s Approach", RAPID EXCAVATION & TUNNELING, Washington, DC: 180-189.
[17]         Goodman, R. E., Van, T. K., & Heuze, F. E., (1968), "Measurement Of Rock Deformability In Boreholes", The 10th U.S. Symposium on Rock Mechanics (USRMS), Austin, Texas.
[18]         Kavur, B., Cvitanović, N. Š., & Hrženjak, P.,(2015), "Comparison between plate jacking and large flat jack test results of rock mass deformation modulus", International Journal of Rock Mechanics and Mining Sciences, 73, 102-114.
[19]         ISRM, (1978), "Suggested Methods for Determining In Situ Deformability of Rock", ISRM Commission on Standardization of Laboratory and Field Tests,
[20]         ASTM, (2008), "Standard Test Method for Determining the In Situ Modulus of Deformation of Rock Mass Using the Rigid Plate Loading Method", West Conshohocken, United States, D 4394 – 08.
[21]         ISRM,(1979), "Suggested methods for determining in-situ deformability of rock- Part I: Suggested method for deformability determination using a plate test", International Journal of Rock Mechanics  Mining Sciences and Geomechanics, 16, 197-202.
[22]         ASTM, (1998), "Standard Test Method for Determining the In Situ Modulus of Deformation of Rock Mass Using the Flexible Plate Loading Method", West Conshohocken, United States, D 4395 – 98.
[23]         Unal, E.,(1997), "Determination  of  in-situ deformation modulus:  New  approaches  for plate loading  tests", International Journal of Rock Mechanics and Mining Sciences, 34, 897-915.
[24]         Palmstrom, A. (2009). "Combining the RMR, Q, and RMi classification systems." from www.rockmass.net.
[25]         Singh, B. and R. K. Goel, (2011), "Engineering Rock Mass Classification, Tunneling, Foundations, and Landslides", Waltham, Elsevier Inc.
[26]         Hoek, E., Carter, T. G., & Diederichs, M. S., (2013), "Quantification of the Geological Strength Index Chart", 47th U.S. Rock Mechanics /Geomechanics Symposium, San Francisco, California American Rock Mechanics Association.
[27]         Rahimi, B., Shahriar, K., & Sharifzadeh, M., (2014), "Evaluation of rock mass engineering geological properties using statistical analysis and selecting proper tunnel design approach in Qazvin–Rasht railway tunnel", Tunnelling and Underground Space Technology, 41, 206-222.
[28]         David, H. A. and J. L. Gunnink,(1997), "The Paired t Test Under Artificial Pairing", The American Statistician, 51(1), 9-12.
روش های تحلیلی و عددی در مهندسی معدن
دوره 8، شماره 16
آبان 1397
صفحه 95-106

فایل ها

سابقه مقاله

  • تاریخ دریافت: 04 مهر 1394
  • تاریخ بازنگری: 13 مهر 1395
  • تاریخ پذیرش: 20 آذر 1395

هم رسانی

ارجاع به این مقاله

آمار