MODEL EXPERIMENT STUDY ON THE DIFFERENT REINFORCEMENT EFFECTS OF UN-BONDED ANCHOR CABLE AND FULL-LENGTH BONDED ANCHOR CABLE IN ROCK ENGINEERING

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1 24 15 Vol.24 No Chinese Journal of Rock Mechanics and Engineering Aug ( ) TU 457 A (2005) 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 China 2. Department of Modern Mechanics University of Science and Technology of China Hefei China 3. School of Civil Engineering and Architecture Wuhan University of Technology Wuhan 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 (1968 ) chenanmin@126.com

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.

2 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 6] [7 9] [10] cm 64.5 cm 20 cm( ) 15 cm 10 ( 1 2) cm φ 2 mm 4 cm φ 0.8 mm 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

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.

3 II III IV IV V 1 Table 1 Characteristics of experimental models ( ) I II III 15 N IV 30 N V 30 N 3 3 P v P v 2.2 R c ( θ = 0 ) ( θ = 90 ) u D 2 Table 2 Displacements of underground openings u 10 2 D (θ = 0 ) (θ = 90 ) I IV V Table 3 Comparison between the initial failure load and collapsing load of the underground openings P / R v c P / R v c I IV V (1) 2 (1) 2 (IV) 17% 35% 25% 40% (IV) 67% (2) 2 68% (2) 2 10% 2 53%( ) 36%( )

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.

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 = R 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 = 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 ( ) (1) = 1.41 = 1.65 = 1.76

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.

5 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 = = ( ) 3.1 2

5 Radial and circular strain distribution along the skewback orientation (θ = 90 ) during the overloading test of the

6 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 = (b) τ - u 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% % 2 ( 10) ( 11) ( ) 8 Fig.8 Comparison of the shear strengths of anchored model and un-anchored model 4 (2) ( 9)

9 Comparison of the shear strengths of anchored rock 3.

7 (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

8 and Soil. New Techniques in Rock-soil Anchorage Engineering[M]. Beijing China Communications Press 1998.(in Chinese)) and calculating method of inner bonding section of prestressed cables within rock mass[j]. Journal of Yangtze River Scientific Research [2]. [M]. Institute (3) (in Chinese)) 1996.(Xiong Houjin. New Progress of International Anchoring and Grouting Techniques for Geotechnical Engineering[M]. Beijing China Architecture and Building Press 1996.(in Chinese)) [7]. [J]. OVM 2000 (1) (Tian Yujia Lu Bing Huang Jiaqi et al. New series of anchor cable structures and its applications in [3]. [J]. engineering[j]. Communication of OVM 2000 (1) (in 2002 (4) 3 8.(Gao Dashui. The application and development of prestressed anchorage techniques in the high rock slop of the permanent ship-lock of the Three Gorges Project[J]. Anchorage Engineering in Rock and Soil 2002 (4) 3 8.(in Chinese)) Chinese)) [8]. [J] (2) (Yang Junzhi Chen Yanhong Cui Jinhai et al. Application in engineering practice of pull-compressed composite anchor cable with un-bonded section[j]. [4]. Anchorage Engineering in Rock and Soil 2001 (2) (in [J] (2) (Zhang Hongbo Huang Maosong Song Xiuguang et al. Analysis of influencing factors of prestressed cables in reinforcing landslide mass[j]. Rock and Soil Mechanics (2) (in Chinese)) Chinese)) [9]. [J] (5) (Han Jun Ding Xiuli Zhu Jiebing. New progress on anchorage techniques in rock-soil[j]. Journal of [5]. Yangtze River Scientific Research Institute (5) [J] (2) (Zhang Faming Liu Ning Chen Zuyu et al. Analysis of factors affected on load losses of high capacity and long rock anchors[j]. Rock and Soil Mechanics (2) (in Chinese)) 72.(in Chinese)) [10]. [J] ( ) (Gu Jincai Shen Jun Chen Anmin et al. Physical model tests [6]. research on force response characteristics of underground openings [J] (3) (Xu Nianfeng Mu Chunxia Wang Li. Exploration on working mechanism reinforced by anchor cables[j]. Chinese Journal of Rock Mechanics and Engineering (Supp.) (in Chinese))

(in Chinese)) 1996.(Xiong Houjin. New Progress of International Anchoring and Grouting Techniques for Geotechnical Engineering[M]. Beijing China Architecture and Building Press 1996.(in Chinese)) [7].

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