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Abstract In order to reveal the pullout mechanism of tunnel-type anchorages，the deformation characteristics and the potential failure patterns of surrounding rocks and to verify the design safety factor of the tunnel-type anchorage，a field model test with the similarity ratio of 1∶25 for tunnel-type anchorage was conducted in the exploration cave of the Puli Bridge. By performing the elasto-plastic and rheological tests under different loading conditions，the load transmission，deformation distributions and rheological characteristics of the anchorage and surrounding rocks were obtained. The test results show that the distribution curves of maximum deformation at the rear surfaces of anchorage and surrounding rocks exhibit symmetrical double-peak shapes，and those of the frontal surfaces exhibit upward convex shapes. The deformations at the rear surface are bigger than those at the frontal surface. The maximum deformation under 8P load(where，P is the design load) is only 61 μm，and the maximum deformation under 50P load is 566 μm. Due to the clamping effects of the surrounding rocks，the stress in the rear end diffuses very slowly to the front under overloading conditions. Under 50P load，the strain in the front end is only 3% of that in the rear end. The stress concentration clearly occurs at the rear end of the concrete anchorage and the strain is partly irreversible，i.e. the plastic deformation occurs. Having considered that the quality of rock masses at the testing area is better than the one of the prototype tunnel-type anchorage，the overloading stability coefficient is recommend to be larger than 8. As there is no observed rheological behavior under 6P load，the long-term stability coefficient is considered to be larger than 6.
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Received: 12 December 2013
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2015, Vol. 34 
