Layered Rock Tunnel Stability And Controlled Blasting Techniques

In the surrounding rock is layered one, the existence of bedding joints not only causes its anisotropy to be extremely remarkable, at the same time makes it discontinuous. When tunnels are constructed in the horizontal layered rock mass, the deformation and demolishment of the surrounding rock are complex and the problem of stability is quite prominent. In this paper, for the characteristics of layered rock, use the background of the tunneling projects on Ji-Huai Expressway in Hunan Province, the surrounding rock stability and blasting technique for controlling are studied deeply using MIDAS/GTS in this thesis. The numerical model is builded on the basis of field investigation, the influence of the stratification planes considered. The main work of this thesis are the followings:1,According to destruction mechanism of layed rockmass and the relationship between the chamber axis and the attitude of bed, divides the layed rockmass chamber into four kinds of destruction pattern such as bend-fall, curve-bend, frontier wall bend, ledger wall blows up, and has analyzed the influence factors in tunnel with layered rockmass.2,Numerical model is builded in which various laminations are regarded as the isotropic continuous medium and the influence of stratification plane is considered. Then a project is used to verify the accuracy of the model. And the model is certificated reliable through contrasting the computed result and the spot measurement.3,Analysing the laws of the plastic failure, deformation and stress change in rock on the condition of different degree and thickness. The influence on the surrounding rock stability of tunnels because of the different mechanics parameters of stratification plane is obtained.4,The dynamic stability of surrounding rock and ground motion effects were analyzed and compared between rock on the condition of different degree, we obtain the regulation of characteristic point's vibrate speed, acceleration and defeat district of shear srtain.5,Reasons of the excessive and deficient excavation in horizontal layer surrounding rock for soomth blasting were analyzed, combined with blasting numerical simulation results, the corresponding measures were constituted, and by using field test to obtain the decay law of tunnel blasting vibration in horizontal layered rockmass.