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| MUTUAL INFLUENCE BETWEEN SHEAR DILATATION OF ROCK MASS AND REBAR SUPPORT AROUND UNDERGROUND EXCAVATION |
(1. Beijing Research Institute of Uranium Geology，Beijing 100029，China；2. School of Civil and Environmental Engineering，University of Science and Technology Beijing，Beijing 100083，China；3. School of Engineering，Laurentian University，
Sudbury，P3E 2C6，Canada；4. School of Resources and Civil Engineering，Northeastern University，Shenyang，Liaoning
110004，China) |
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Abstract Taking the medium-fine-grained soft rock for example，the influence of shear dilatation of rock mass on the axial force distribution of fully grouted rebar bolts is analyzed. The difference in variable rock dilatation and constant rock dilatation on rebar behavior in rock mass is investigated. In addition，the suppressing effect of rebar on shear dilatation of rock mass near excavation is discussed. For the constant shear dilatation angles，the axial forces increase with increasing shear dilatation angles；and the gradient of axial forces shows an increasing trend. However，the assumption of constant shear dilatation angle cannot describe that the shear dilatation is dependent on confining pressure and plastic deformation，leading to underestimating axial force of rebar bolts near excavation and to overestimating axial force of rebar bolts from excavation boundaries. The established shear dilatation angle model considering both confinement and plastic shear strain reveals the large tensile loading on rebar bolts at low confinement conditions；and a rapid decrease in axial forces with increasing confining pressures can be observed，which is in agreement with actual behavior of rebar bolts observed in underground openings. The rebar bolts reinforcement improves the confining pressure near excavation and suppresses the large shear dilatation of rock mass. In the underground engineering design，the rock support under low confinement conditions should be considered to effectively control the rock deformation and failure.
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Received: 12 May 2010
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2010, Vol. 29 
