岩体流变对岩壁吊车梁锚杆应力的影响

Influence of Rheology on Bolt Stress of Rock-anchored Beam

流变是岩体的固有力学性质,对地下厂房开挖和运行的安全稳定性具有重大影响。但岩壁吊车梁设计时多采用仅考虑岩壁吊车梁自身所受荷载的刚体极限平衡法,忽略了围岩变形尤其是岩体流变变形的影响。因此,结合某水电站地下厂房工程,建立地下厂房系统有限元模型,基于岩体Drucker-Prager弹塑性本构关系和考虑时间硬化的等效流变原理,研究了地下厂房开挖过程和正常运行10年后岩体流变对岩壁吊车梁锚杆应力的影响。结果表明,在地下厂房正常运行10年后下游顶部第一排受拉锚杆在长度6.72 m处应力值达317.83 MPa,随着地下厂房运行时间的延长,岩壁吊车梁锚杆应力值逐渐变大,但应力变化速率逐渐减小,有必要采取工程措施,以便防止随着时间的延长岩体流变量逐渐增长,从而使岩壁吊车梁锚杆发生屈服。

Rheology is the inherent mechanical properties of rock mass,which has great influence on safety and stability of excavation and operation of underground powerhouse.The rock-anchored beam is designed with the rigid limit equilibrium method only considering the load of the rock-anchored beam itself,while the influence of the surrounding rock deformation,especially the rheological deformation of the rock mass is neglected.Therefore,the FEM model of underground powerhouse system is established for a hydropower station.The Drucker-Prager constitutive relation of rock mass and the equivalent rheology principle of time hardening are used to analyze the impact of rheology on the bolt stress of rock-anchored beam during the excavation process after 10 years normal operation.According to the calculations,it is shown that after 10 years normal operation,the stress reached 317.83 MPa at 6.72 mon the first row of the tension bolt.During the normal operation of the underground powerhouse in ten years,the bolts stress of the rock-anchored beam is increased,while the stress increased rate is gradually reduced.Therefore,engineering measure should be taken to prevent the bolts yield from the gradual increase of rock mass rheological.