摘要
通过分析原始垂直地应力对圆形地下洞室塑性区半径、围岩体塑性区和弹性区内岩体的位移变化以及对锚杆应力分布的影响,揭示原始垂直地应力对锚杆锚固效果的影响。研究结果表明,弹性区内任一点的应力大小与垂直地应力有关,而塑性区内任一点的应力与原始垂直地应力无关;随着垂直地应力的增大,巷道塑性区半径也在不断增大,二者之间呈明显的非线性关系;塑性区的径向位移及隧洞壁的最大位移也随之增大。同时,根据围岩与锚杆的相互作用,建立全长注浆岩石锚杆在圆形隧洞围岩中的应力分布解析本构方程。在此解析模型的基础上,对不同垂直地应力作用下锚杆的应力分布模式进行较详细分析,得出随着垂直地应力增大,锚杆的摩阻力和轴向载荷也随之增大,并且锚杆端部的应力集中现象更加明显,当锚杆端部的摩阻力超过围岩的容许抗剪强度时,则锚杆与围岩发生开裂破坏,故在设计与施工中应予以考虑。最后,提出提高和改善由于锚头开裂导致锚固效果降低的方法,对全长注浆岩石锚杆施加垫板,能有效改善锚杆的锚固效果。
By analyzing the effects of initial vertical geostress on plastic zone radius of circular underground tunnel, displacement changes in plastic and elastic zones of surrounding rock and bolt stress distribution mode, it is revealed that the initial vertical geostress is very important for reinforcement effect. The study results show that the stresses in elastic zone are related with the vertical geostress, but the stresses in plastic zone are opposite. With the vertical geostress increasing, the radius of plastic zone increases; and there is a nonlinear relation between the vertical stress and the radius of plastic zone. The radial displacements in plastic zone and the maximum displacement of tunnel wall increase with the increase of the vertical geostress. Based on the interaction between rock mass and rock bolt, the analytical constitutive equations of stress distribution of fully grouted rock bolt in surrounding rock of circular tunnel are built. On the basis of the model, the stress distribution mode of bolt under different vertical geostresses is analyzed. It is shown that the friction resistance and the axial load increase with the increasing vertical geostress, and stress concentration appears at bolt end more obviously. When the friction resistance at bolt end is more than the allowable shear strength of surrounding rock, the cracking failure happens in bolt and surrounding rock, which should be considered in design and construction. Finally, the method for improving the reinforcement effect when the anchor head cracks is put forward. It is suggested that setting plate can improve the reinforcement effect of fully grouted rock bolt.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2009年第A01期2928-2934,共7页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(50679015)
关键词
岩石力学
垂直地应力
注浆岩石锚杆
摩阻力
rock mechanics
vertical geostress
fully grouted rock bolt
friction resistance
