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Published byIzabella Pauling Modified over 2 years ago

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3 Generally, support system for a tunnel is designed by some analytical calculation + experience Designs are often suitable but not optimum In this paper selection is optimised and ranked Selection process is assumed to be a multi-criteria decision making problem

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Optimum support system is chosen for C1 tunnel of Tabas coal mine of Iran C1 is the main entry of the mine → Long life → Support system is important 4

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Uni-axial compressive strength: 10.7 MPa Tensile strength based on Brazilian test: 1.3 MPa Young’s modulus: 4385 MPa Poisson’s ratio: 0.25 Friction angle: 35 degrees Cohesion: 5 MPa Vertical and horizontal in-situ stresses: 12.50, and 4.71MPa 5

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6 The geometry of tunnel is defined Geomechanical parameters of the surrounding rock mass were input to the model Potential values for failure and displacement parameters are calculated Various support systems are applied in the model and the stability of the tunnel after application of each support system is determined

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No.Support system explanationIndex 1Supporting by B40 shotcrete 5 cm in thicknessA 2Supporting by B40 shotcrete 8 cm in thicknessB 3Supporting by B40 shotcrete 8 cm in thickness together with rock boltsC 4Application of roof piping together with cement injectionD 5Application of rock bolts to the gallery, roof and sidesE 6Application of steel arches with 1m spacingF 7Application of steel arches with 0.5 m spacingG 8Supporting by B50 shotcrete, 5 cm in thicknessH 9Supporting by B50 shotcrete, 8 cm in thicknessI 10Application of steel arches with 1 m spacing together with rock boltsJ 8

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Model index Displacement at point (cm) The maximum stress on tunnel circumference (MPa) Safety factor 1234 A B C D E F G H I J

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14ab c d EMV EMV

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Step 1: Hierarchy Tree Step 2: Decision Making Matrix Step 3: Pair-wise Comparison Matrix Step 4: Normalized Matrix Step 5: Relative Weights Step 6: Attributes Weights Vector 17

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Alternatives Criteria Goal 19 Support SystemCDGJ Weight The overall inconsistency < 0.1 is acceptable

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CDGJ C C C C C C C Criteria Support Systems with safety factor > 2 22

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A*A* A-A- C C C C C C C positive ideal solutionnegative ideal solution 23

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Support system Positive distance Negative distance Relative closeness 24

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Step 1: deviation matrixStep 2: preference functionsStep 3: preference index and matrixStep 4: outgoing flowsStep 5: entering flowsStep 6: ranking 26

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C1C2C3C4C5C6C7 C-D: C-G: C-J: D-C: D-G: D-J: G-C: G-D: G-J: J-C: J-D: J-G: support systems Criteria 27

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CriteriaC1C2C3C4C5C6C7 Threshold C1C2C3C4C5C6C7 P(C,D) P(C,G) P(C,J) P(D,C) P(D,G) P(D,J) P(G,C) P(G,D) P(G,J) P(J,C) P(J,D) P(J,G) Preference function 28

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CDGJ C D G J support system 29 Matrix of preference indexes Preferenceindex Preference index Preference function Weight of the ith attribute

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CDGJ Outgoing flow Entering flow Net flow support system 30 Outgoing flow Entering flow Net flow

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Preference1234 AHPJGCD TOPSISJGCD PROMETHEEJCGD J: Application of steel arches with 1 m spacing together with rock boltsG: Application of steel arches with 0.5 m spacingC: Supporting by B40 shotcrete 8 cm in thickness together with rock boltsD: Application of roof piping together with cement injection 31

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