تاریخ دریافت: 08 مهر 1395،
تاریخ بازنگری: 18 آبان 1396،
تاریخ پذیرش: 21 آذر 1396
چکیده
طراحی سازه‌های زیرزمینی باید با توجه به شرایط ساختاری توده‌سنگ صورت گیرد. در این زمینه شرایط قرارگیری درزه‌ها، زوایه آنها نسبت به فضای زیرزمینی و زاویه درز‌ها نسبت به هم از اهمیت ویژه‌ای برخوردار است. در این مطالعه پایداری ساختاری تونلی با مقطع نعل اسبی در توده‌سنگ درزه‌دار حاوی دو دسته درزه با فاصله‌داری‌های متفاوت مورد بررسی قرار گرفت. برای مدلسازی درزه‌ها پارامترهای سختی برشی درزه‌ها، شیب دسته درزه‌ها، بازشدگی و فاصله‌داری، نسبت فاصله‌داری درزه‌ها به عرض دهانه تونل () و نسبت تنش‌های برجا به عنوان متغیرهای مدلسازی در نظر گرفته شد. مساحت زون ریزش با تغییر هر یک از شاخص‌ها به طور جداگانه محاسبه شد و بهترین حالت ممکن که دارای کمترین سطح زون ریزش است، تعیین شد. نتایج نشان داد که اگر اختلاف شیب دو دسته‌درزه کمتر از 40 درجه باشد بیشترین سطح زون ریزش تشکیل می‌شود و افزایش اختلاف شیب دسته درزه‌ها بیش از 40 درجه موجب کاهش سطح ریزش می‌شود. همچنین افزایش نسبت فاصله‌داری درزه‌ها به عرض دهانه تونل منجر به افزایش مساحت زون ریزشی و ناپایداری بیشتر می‌شود. ناپایداری در نسبت مذکور در بازه‌های 11/0 تا 33/0 وجود دارد و برای مقادیر بیش از 33/0 برای نسبت ذکر شده به علت افزایش ابعاد بلوک و عدم امکان ریزش، ناپایداری به صفر می‌رسد. ایمن‌ترین حالت و کمترین مساحت زون ریزش در نسبت و بیشترین مساحت در نسبت اتفاق افتاد.
Numerical Investigation of the Influence of Geometrical and Mechanical Parameters of the Intersecting Joint Sets on the Area of Failure Zones around Tunnel
Dept. of Mining, Shahid Bahonar University of Kerman, Iran
چکیده [English]
Summary One of the important problems in designing underground structures is geometrical and mechanical parameters of joint sets. Therefore designing underground structures should be done according to the structural conditions of the rock mass. In this regard, it is important to consider joint condition and spatial position of joints toward the underground excavation. In this study, using UDEC software, the structural stability of a tunnel with a horseshoe cross section in an intersecting jointed rock mass is investigated. Rock mass was containing two joint sets with different joint spacing. In the numerical models, joint shear stiffness, joint dip, joint opening, joint spacing, the ratio of joint spacing to width tunnel (l/b) and in situ stress were considered as variables. The area of failure zone was calculated separately by changing abovementioned parameters and the best condition concerning the least failure zone was determined. According to results, the largest failure area will created when dip difference between joint sets is lower than 40 degree, and further increasing of dip difference between joint sets causes reduction of area of failure zone. Also, increasing the ratio of joint spacing to tunnel width, leading to increase of the area of failure zone and consequently increase of instabilities. Instability exist in the range of this ratio from 0.11 to 0.33, and increasing of the ratio more than 0.33 provides improvement of stability condition (i.e., instability approaches zero) due to increasing block size and impossibility of block caving. The safest situation regarding minimum and maximum area of failure zone will occur for l/b=0.11 and 0.33, respectively.
Introduction In this research, the effective parameters of jointed rock mass, which affect the tunnel stability and the extent of the failure zone, were examined. The final shape of failure zone has presented in a table. Also the safest situation of intersecting joints has introduced.
Methodology and Approaches UDEC software has the ability of modeling jointed rock masses by considering the characteristics of joints. Therefore, using this software, the extent of the failure zone were calculated.
Results and Conclusions In this research, the area and the shape of failure zone of a jointed-rock are analyzed and the effect of main parameters on tunnel stability are discussed.
کلیدواژه ها [English]
Stability analysis, Joint, Geometrical parameters, numerical modeling, Area of failure zone, UDE
مراجع
[1] Goodman, R.E., (1989), Introduction to rock mechanics, John Wiley & Sons.
[2] Bieniawski Z.T., (1973), Engineering classification of jointed rock masses, Trans. S. Afr. Inst. Civil Engineering; 15(12):335–44.
[3] Jia, p. Tang, C.A, (2007), Numerical study on failure mechanism of tunnel in jointed rock mass, Tunneling and Underground Space Technology.
[4] Lee, D-H,2003,A parametric study of the discontinuity in rock mass and its influence on tunnel behavior, Technology roadmap for rock mechanics, South African Institute of Mining and Metallurgy.
[5] Bieniawski, Z.T., (1984), Rock Mechanics Design in Mining and Tunneling, A.A. Balkema, Rotterdam.
[6] Cecil, O.S., (1970),Correlations of Rock Bolt - Shotcrete Support and Rock Quality Parameters in Scandinavian Tunnels, Ph.D. thesis University of Illinois, also in Proc. Swedish Geotech. Institute, No. 27.
[7] Madkour, H, (2012), Parametric analysis of tunnel behavior in jointed rock”, Ain Shams Engineering Journal.
[8] DalgIç S., (2003), Tunneling In Fault Zones, Tuzla Tunnel, Turkey, Tunneling and Underground Space Technology, Vol. 18, No. 5, 453-465.
[9] NikAdat, N (2014). “Investigating the effect of the geometric properties of discontinuities on stress distribution around underground spaces by boundary element method and finite element method”, Master of Science thesis, Mining and Metallurgy faculty, Rock mechanics, Yazd University, Iran. (In Persian).
[10] Zare Rashkooye, H and Emami meybodi, E. (2008). “Numerical analysis of the influence of geometrical and geomechanical properties of joints on the behavior of tunnel”, the third Iranian Rock Mechanics Conference, Amirkabir University of Technology, Tehran, Iran. (In Persian)
[11] Esterhuizen, G.S., Iannacchione, A.T, (2005), Effect of Dip and Excavation Orientation on Roof Stability in Moderately Dipping Stone Mine Workings, Alaska Rocks, Proceedings of the 40th U.S. Rock Mechanics Symposium, Anchorage, Alaska.
[12] Hoseyni and Etemadi, (2014). “The effect of Angle intersection of two discontinuities on the stability of the tunnel”, Seventh Conference of geology and the environment of Iran. (In Persian)
[13] ITASCA consulting group, UDEC, (2000).
[14] Regulations of road and rail tunnels SNIP II-44-78.
ابتدای صفحه