地下工程岩体剪胀与锚杆支护的相互影响

 探讨隧道开挖边界附近的岩体剪胀对全长黏结式锚杆轴力分布的影响，区分依赖围压和塑性剪切应变的岩体剪胀与恒定的岩体剪胀对锚杆支护作用影响的差异性，分析锚杆对岩体膨胀的抑制作用。研究结果表明，对于恒定的剪胀角值，锚杆轴力随着剪胀角的增加而增加，且梯度亦随之增加，但其不能反映剪胀对隧道围压和岩体塑性变形的依赖关系，从而低估锚杆在低围压区域内遭受的张拉荷载，并高估高围压区域的所受的张拉荷载。由剪胀角模型计算得出的锚杆轴力分布突显锚杆在低围压环境下承受的较大张拉荷载状态，以及围压增加导致其轴力快速降低的行为趋势，能够合理反映锚杆在地下工程应用中的力学行为。由于锚杆支护增加岩体围压，抑制高剪胀区的扩展，从而减小隧道围岩的变形。在地下工程支护设计中，应重点支护紧邻开挖面低围压环境的岩体以有效地控制其破坏和膨胀变形。

MUTUAL INFLUENCE BETWEEN SHEAR DILATATION OF ROCK MASS AND REBAR SUPPORT AROUND UNDERGROUND EXCAVATION

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.