24 15 Vol.24 No.15 2005 8 Chinese Journal of Rock Mechanics and Engineering Aug. 2005 1 1 2 3 (1. 471023 2. 230026 3. 430070) 2 2 2 2 2 TU 457 A 1000 6915(2005)12 2689 08 MODEL EXPERIMENT STUDY ON THE DIFFERENT REINFORCEMENT EFFECTS OF UN-BONDED ANCHOR CABLE AND FULL-LENGTH BONDED ANCHOR CABLE IN ROCK ENGINEERING CHEN An-min 1 SHEN Jun 1 2 GU Xin 3 (1. The Third Research Institute of the Corps of Engineering General Staff of CPLA Luoyang 471023 China 2. Department of Modern Mechanics University of Science and Technology of China Hefei 230026 China 3. School of Civil Engineering and Architecture Wuhan University of Technology Wuhan 430070 China) Abstract The different reinforcement effects of the two typical anchor cables un-bonded anchor cable and full-length bonded anchor cable are studied by model experiments of the underground openings and the shear strength of rock mass structural planes. The different reinforcement effects and characteristics of the two typical anchor cables are analyzed and compared by the excavation displacement failing loads load-displacement characteristics strain distribution characteristics of the underground opening wall and the macroscopic damage process of the openings and etc.. By shear tests of reinforced specimen with structural planes and that without structural planes the different reinforcement effects of the two typical anchor cables on rock mass structural planes are compared. The comparison results of peak shear strength of the reinforced specimen and the variation characteristics of the tensile force of the two typical anchor cables in shearing process are given. The tensile force of the un-bonded anchor cable increases with the shear displacement however the tensile force of the full-length bonded anchor cable has almost no change in shearing process. Based on the comprehensive comparison of the reinforcement effects of the two typical anchor cables some suggestions on the design of reinforcement 2004 08 17 2005 02 29 (1968 ) 1990 E-mail chenanmin@126.com
2690 2005 engineering are put forward. Key words rock mechanics un-bonded anchor cable full-length bonded anchor cable reinforcement effect underground openings model experiment shear strength experiment of rock mass structural planes 1 5 2 2 [1 6] [7 9] 2 2.1 [10] 3 64.5 2 cm 64.5 cm 20 cm( ) 15 cm 10 ( 1 2) cm φ 2 mm 4 cm φ 0.8 mm 2 1.7 MPa PYD 50 2 I P v = 1.2 MPa P H = 0.3 MPa N = P H /P v = 1/4 8 2 P v L = 10 cm L = 4 cm 1 Fig.1 Structure of un-bonded anchor cable(uac) 64.5 cm P H = 1/4P v D = 15 cm 64.5 cm 2 Fig.2 Structure of full-length bonded anchor cable 3 0 Fig.3 Sketch of the model of reinforced underground openings
24 15. 2691 5 1 II III IV IV V 1 Table 1 Characteristics of experimental models ( ) I II III 15 N IV 30 N 2.3 2 V 30 N 3 3 P v P v 2.2 R c ( θ = 0 ) ( θ = 90 ) + 2 2 u D 2 Table 2 Displacements of underground openings u 10 2 D (θ = 0 ) (θ = 90 ) I 2.00 1.33 IV 0.70 0.33 V 1.33 0.91 3 Table 3 Comparison between the initial failure load and collapsing load of the underground openings P / R v c P / R v c I 1.41 1.5 IV 1.65 2.0 V 1.65 2.2 2 3 (1) 2 (1) 2 (IV) 17% 35% 25% 40% (IV) 67% (2) 2 68% (2) 2 10% 2 53%( ) 36%( )
2692 2005 4 (1) (2) 2.4 (3) 2 (OA ) 2 AB 4 O 2.5 u v / D 2 4 Fig.4 Load-displacement curves of the underground opening 5 5 = θ 90 wall in vault-floor orientation 5 3 P v /R c = 0.95 1.18 1.41 R 0 2 5 2 K v = P v /u v MPa/m (N/m) MPa u v (mm) K v = Pv / uv OA AB BC ( 4) 2.6 R v / R c = 1.0 1.5 2.0 Table 4 4 Convergent deformation stiffnesses of the underground opening /(MPa m 1 ) OA AB BC I 1 104(1.00) 360(0.33) 144(0.13) IV 1 584(1.43) 480(0.43) 284(0.26) V 1 173(1.06) 925(0.84) 386(0.35) OA 2 6 6 1 ( ) (1) = 1.41 = 1.65 = 1.76
24 15. 2693 P v /R c = 0.95 P v /R c = 1.18 P v /R c = 1.41 εθ /(10 3 µε) εθ /(10 3 µε) R/R 0 εr /(10 3 µε) (a) εr /(10 3 µε) R/R 0 R/R 0 R/R 0 (b) 5 (θ = 90 ) Fig.5 Radial and circular strain distribution along the skewback orientation (θ = 90 ) during the overloading test of the underground openings (a) (b) 6 2 Fig.6 Comparison of the failure shapes of the underground openings reinforced by un-bonded anchor cables and full-length bonded anchor cables (2) 2 = 1.65 2 = 1.65 1.76 1.88 2.00 2.24 2.35 3 ( ) 3.1 2
2694 2005 2 2 40 cm 40 cm 40 cm( ) 7 mm 7 Fig.7 Sketch of the shear experiment model of reinforced rock mass (a) 5 φ 2.5 mm 3 α = 60 75 90 2 (b) τ - u 2 9 2 Fig.9 Comparison of the shear strengths of anchored rock 3.2 mass structural planes reinforced by un-bonded anchor (1) ( 8) cables and full-length bonded anchor cables 2 57% 3.3 60% 2 ( 10) ( 11) ( ) 8 Fig.8 Comparison of the shear strengths of anchored model and un-anchored model 4 (2) ( 9) 2 4.1 2
24 15. 2695 (a) (b) 10 Fig.10 Variation characteristics of the tensile force of full-length bonded anchor cables (a) (1) 2 (2) 2 (3) 2 (4) 4.2 (1) (2) (3) (References) (b) 11 [1]. [M]. Fig.11 Variation characteristics of the tensile force of un-bonded anchor cables 1998.(Chinese Association for Anchorage Engineering in Rock
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