Mechanics Analysis And Numerical Emuation Test On The Fully Grout-ed Bolts In Tunnel

Bolt support system has been applied widely in Geotechnical engineering ,but the research on work mechanism and designing method of bolt is mainly performed by lab experiment and in-situ tests .It is still a shortage of utilizing FEM method to study the detail properties of the bolted rock mass.In this paper, the systemic numerical tests on bolt support are made utilizing FEM method focused on the influence of bolts to inner force of supporting structure and the rock stress and deformation properties.Firstly, the relation between the ultimate tensile of the bolt and interface cohesive intensity between the bolt and rock is analyzed through the pulling-out test, on the basis of analyzing mechanism of bolt spreading force, an analytical model is proposed to predict the axial force and shear stress on the grouted bolt surface for tunnel bolting. Then compared with data of pulling-out test of bolt ,a numerical test model which embody correctly condition of bolt supporting is set up. The systemic numerical tests on bolt support in tunnels with weak interbed are then carried out, and the reinforce mechanism of bolt support are discussed. Finally , through researching the influence of parameters on bolt bearing capacity and supporting effect, the interaction behaviors of the rock bolt and rock mass his further described. Main conclusions can be:1, The interaction mechanism of the rock bolt and rock mass is theoretically analyzed in pulling-out tests and the relationship between the ultimate tensile force and interface cohesive intensity is established.2, AN analytical model to predict inner force on grouted rock bolt for tunneling is also proposed, it is meaningful to describe the mechanics characteristics of bolt and its main factors on mechanics characteristic of bolt.3, Through analyzing inner force and distortion of the supporting structure and rock mass, the reinforce mechanism of bolt support are further described4, The interaction mechanism of the rock bolt and rock mass change law of inner force and distortion about supporting structure is also described, to provide a quantitative evaluation for bolt supporting effect.