تحلیل پایداری و طراحی سیستم نگهداری موقت محل انشعاب تونل‏های پنستاک از تونل انتقال آب سد رودبار لرستان با استفاده از نرم افزار FLAC 3D

نوع مقاله: گزارش فنی

نویسندگان

دانشکده مهندسی معدن، دانشگاه صنعتی اصفهان

10.29252/anm.7.13.113

چکیده

امروزه سازه‏های بزرگ زیرزمینی به‌منظور توسعه راه و راه‏آهن، انتقال آب، ذخیره‏سازی نفت و گاز، نیروگاه‏های زیرزمینی، دفن زباله‏های اتمی و غیره احداث می‏شوند. از مهم‌ترین اهداف طراحی این فضاها، ارزیابی پایداری و در صورت لزوم طراحی سیستم نگهداری آنها است. در این پژوهش، پایداری محل انشعاب تونل‏های پنستاک از تونل انتقال آب سد رودبار لرستان بررسی شده است. با تجزیه و تحلیل آماری روی نتایج حاصل از آزمایش‏های آزمایشگاهی و برجای انجام شده در ساختگاه سد، روابط تجربی موجود و اعمال قضاوت مهندسی، پارامترهای ژئومکانیکی توده سنگ محل انشعاب تعیین شد. با توجه به ضعیف بودن توده سنگ محل انشعاب، محیط سنگی محل انشعاب، به صورت محیط پیوسته در نظر گرفته شد و با استفاده از نرم‌افزار FLAC3D، مدل‏سازی گردید. با توجه به نتایج حاصل از مدل‏سازی عددی و نیز تعیین ناحیه تأثیر (زون پلاستیک)، جهت مهار جابجایی‏ها و پایدارسازی فضای مذکور، سیستم نگهداری موقت به صورت ترکیبی از شاتکریت و شبکه پیچ سنگ با طول مناسب طراحی شد. مقادیر بیشینه جابجایی به وجود آمده در سقف، کف و دیواره‏های فضای محل انشعاب، پس از 16 مرحله حفاری و نصب سیستم نگهداری، نشان دهنده پایداری فضای محل انشعاب و مناسب بودن فاصله بین دو تونل پنستاک از یکدیگر است. همچنین بررسی منحنی اندرکنش نیروی محوری- ممان خمشی نشان داد، مقطع شاتکریت طراحی شده پایدار است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Stability Analysis and Support System Design of Penstock Tunnels Bifurcation with Headrace Tunnel of Rudbare-Lorestan Dam Project

نویسندگان [English]

  • Hossein Behzadinejad
  • Lohrasb Faramarzi
  • Mohammad Darbor
Department of Mining Engineering, Isfahan University of Technology, Iran
چکیده [English]

Summary
In this research, stability of penstock tunnels bifurcation with headrace tunnel of Rudbare-Lorestan dam powerhouse was studied. Due to the weak rock masses at the bifurcation area, the numerical modeling using FLAC3D was performed. According to the results of numerical modeling and determination of plastic zone and the empirical methods, the temporary support system consists of shotcrete and rock bolt with adequate length are suggested. Based on laboratory and in situ tests, the geomechanical parameters are determined.
 
Introduction
Today, large underground structures are constructed in order to transfer the water, oil and gas storage, underground power plants, radioactive waste repositories and etc. With the development and upgrade of infrastructures, tunnel construction is increasing all over the world and tunnel engineers are more aware of the importance of the safety and economics of tunnel construction. Stability of underground structures depend on size and geometry of construction, excavation technique, in situ stress conditions and support system and its installation time. 
 
Methodology and Approaches
In order to estimate the deformation modulus of the rack mass in the headrace tunnel, in situ tests including of plate loading and dilatometer tests were performed. Then elasto-plastic behavior was defined for the rock mass by mohr-columb criterion and model was executed numerically to reach static stability. The Bifurcation cavern have been excavated by heading and benching method that is executed through drill and blasting technique.
 
Results and Conclusions
The empirical method suggest shotcrete with rock bolts to support weak rock masses. Also the numerical analysis demonstrate the installation of rock bolts with shotcrete as a temporary support system. Due to the large plastic zone caused by excavation processes, the value of the advancing step 0.8 m was determined. Also, the analysis of rock mass plastic zone in bifurcation area determined a suitable length of 6 meters for rock bolts. During the excavating of rock pillars, the value of change in the axial force acting on the rock bolt in the right wall of the tunnel No. 1, was increased. Also, the excavation of tunnel No. 2 at a distance of 11 meters from the tunnels No. 1, No. 4 and No. 5, was shown the less influence on the value of axial forces applied to the rock bolts. After the 16 stages of excavation advancement steps and installation of support systems, the maximum values of displacement in the roof, floor and walls of the bifurcation, were respectively 2.8, 3.67 and 1.5 cm

کلیدواژه‌ها [English]

  • Penstock Tunnels
  • Geomechanical Parametes
  • Numerical simulation
  • Plastic zone
  • Temporary support system
[1] Moorak, S., & Cording, E. J. (2007). Ground–liner interaction in rock tunneling. Tunnelling and Underground Space Technology, 22(1), 1-9.

[2] Stille, H., & Palmstrom, A. (2008). Ground behaviour and rock mass composition in underground excavations. Tunnelling and Underground Space Technology, 23(1), 46-64.

[3] Hoek, E. (2011). Cavern Reinforcement and Lining Design. prepared for RocNews.

[4] Li, S., Yu, H., Liu, Y., & Wu, F. (2008). Results from in-situ monitoring of displacement, bolt, load and disturbed zone of a powerhouse cavern during excavation process. International Journal of Rock Mechanics and Mining Sciences, 45(8), 1519-1525.

[5] Martin, C. D., Kaiser, P. k., & Christiansson, R. (2003). Stress, instability and design of underground excavations. International Journal of Rock Mechanics and Mining Sciences, 40(7-8), 1027-1047.

[6] Hoek, E. (2007). Practical Rock Engineering. British Columbia, Canada.

[7] Cai, Y., Esaki, T., & Jiang, Y. (2004). A rock bolt and rock mass interaction model. International Journal of Rock Mechanics and Mining Sciences, 41(7), 1055-1067.

[8] Hoek, E. (1999). Support for very weak rock associated with faults and shear zones. The International Symposium on Rock Support and Reinforcement Practice in Mining, Kalgoorlie, Australia.

[9] Zhu, W. S., Sui, B., Li, X. J., & Li, s. c. (2008). A methodology for studying the high wall displacement of large scale underground cavern complexes and its applications. Tunnelling and Underground Space Technology, 23, 651-664.

[10] Malmgren, L., & Nordlund, E. (2008). Interaction of shotcrete with rock and rock bolts- A numerical study. International Journal of Rock Mechanics and Mining Sciences, 45(4), 538-553.

[11] Ghafoori, M., Lashkaripoor, Gh., & Tarigh, S. (2008). Evaluation of geomechanical properties in the headrace tunnel rock masses of Daroongar dam in order to determining of support system. Journal of Iranian Association of Engineering Geology, 1(2), 1-14.

[12] Moeini, E., Hosseini, M., Sharifi, M., & Ebtekar, S. (2010). Stability analysis and design of support system of headrace tunnels of Gotvand dam. Iranian Journal of Mining Engineering, 5(10), 91-96.

[13] Gurocak, Z. (2011). Analyses of stability and support design for a diversion tunnel at the Kapikaya dam site, Turkey. Bull Eng Geol Environ, 70, 41-52.

[14] Jiang, Q., & Feng, X. (2011). Intelligent Stability Design of Large Underground Hydraulic Caverns, Chinese Method and Practice, 4, 1542- 1562.

[15] Ahmadi, A., Shahriar, K., & Asadi, A. (2013). Stability analysis of Amirkabir water conveyance tunnel in strain softening condition using self-similarity method and convergence-confinement curves. Tunneling & Underground Space Engineering, 2(1), 37-48.

[16] Kumar Shrestha, P., & Kanta Panthi, K. (2014). Analysis of the plastic deformation behavior of schist and schistose mica gneiss at Khimti headrace tunnel, Nepal. Bull Eng Geol Environ, 73, 759-773.

[17] Lamas, L. N., Leitao, N. S., Esteves, C., & Plasencia, N. (2014). First infilling of the Venda Nova II unlined high-pressure tunnel: observed behaviour and numerical modelling. Rock Mechanics & Rock Engineering, 47, 885-904.

[18] Dehghani, B., Faramarzi, L., & Sanei, M. (2015). Stability analysis of powerhouse caverns of Bakhtiary dam using 3DEC software. Analytical and Numerical Methods in Mining Engineering, 4(8), 95-108.

[19] Iran Water & Power Resources Development Co. (2007). Engineering Geology Report. Rudbar Lorestan Dam and Powerhouse Plan, Second Phase Studies.

[20] Iran Water & Power Resources Development Co. (2007). Laboratory Tests Report of Rock Mechanics for Rudbar Dam and Powerhouse and Geomechanical Parameters of Dam and Head Race Tunnel. Rudbar Lorestan Dam and Powerhouse Plan, Second Phase Studies.

[21] Behzadi-Nezhad, H. (2011). Stability Analysis and Support System Design of Bifurcation of Penstock Tunnels with Rudbar Dam Powerhouse Headrace Tunnel, M.Sc. Thesis, Department of Mining Engineering, Isfahan University of Technology.

[22] Aksoy, C. O., Kantarci, O., & Ozacar, V. (2010). An example of estimating rock mass deformation around an underground opening using numerical modeling. International Journal of Rock Mechanics & Mining Sciences, 47, 272-278.

[23] Ren, G., Smith, J.V., Tang, J.W., &Xie, Y. M. (2005). Underground excavation shape optimization using an evolutionary procedure. Computers and Geotechnics, 32, 122-132.

[24] Huang, Z., Broch, E., & Lu, M. (2002). Cavern roof stability- mechanism of arching and stabilization by rockbolting. Tunnelling and Underground Space Technology, 17, 249-261.

[25] Tezuka, M., & Seoka, T. (2003). Latest technology of underground rock cavern excavation in Japan. Tunnelling and Underground Space Technology, 18,127-144.