Abstract
Among several design methods of tunnel supporting structure, the load-structure method is widely used in different countries, but the determination of load is essential in this design method. The problem of rockburst is becoming more prominent as tunnel engineering enters the deep underground space. However, the research on the impact load on the supporting structure is insufficient in relevant fields. Therefore, from the perspective of energy, this paper deduces the method and model for calculating the impact load of the rockburst tunnel acting on the supporting structure by using the method of structural mechanics first, after the location effect of impact load is determined under different section types and different section sizes. The results indicated that: dynamic load factor K is related to the stiffness EI and supporting size coefficient K0 of the supporting structure, also the difference of impact load in different sections is proved. Tunnel rockburst-prone location is related to lateral pressure coefficient, thus when λ = 1, the probability of rockburst in the whole circular tunnel is the same, while side wall and vault are prone to rockburst in single-track horseshoe tunnel, and the side wall is prone to rockburst in double-track horseshoe tunnel; furthermore when λ > 1, the vault and the inverted arch are prone to rockburst; additionally, when λ < 1, the rockburst is most likely to occur in the arch waist of the circular tunnel and the side walls and the arch waist of the horseshoe tunnel. Finally, the rockburst tunnel’s local load-structure calculation model and the calculation process based on the model are provided.
Highlights
Geotechnical engineering has long been concerned with deep underground space, and tunnel engineering’s buried depth is increasing, resulting in higher and higher in-situ stress environments
Based on the data research and theoretical analysis method, from the perspective of energy and using the method of structural mechanics, this paper deduces the calculation formula of the impact load acting on the supporting structure of the rockburst tunnel
After obtaining the two key parameters, the size and velocity of the blasting block, the load acting on the supporting structure is estimated by the structural mechanic’s method
Summary
Geotechnical engineering has long been concerned with deep underground space, and tunnel engineering’s buried depth is increasing, resulting in higher and higher in-situ stress environments. More and more calculation methods of tunnel deformation have been proposed [16], the design methods of deep-buried hard rock tunnels for drilling, blasting, anchoring, and grouting in various countries are mainly divided into engineering analogy, load-structure, layer-structure, and theoretical calculation method. The design of rockburst tunnel supporting structures in China and other countries focuses mainly on engineering analogy. Through theauthor’s investigation, there is no complete calculation method to estimate the impact load acting on the supporting structure of the rockburst tunnel. To adopt a load-structure method in designing rockburst tunnel supporting structures, it is necessary to conduct an in-depth study on its impact load. Based on the data research and theoretical analysis method, from the perspective of energy and using the method of structural mechanics, this paper deduces the calculation formula of the impact load acting on the supporting structure of the rockburst tunnel. The local load-structure model of the rockburst tunnel and its calculation flow is derived
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