Abstract
Blasting in water-conveyance tunnels that cross rivers is vital for the safety and stability of embankments. In this work, a tunnel project that crosses the Yellow River in the north district of the first-phase Eastern Line of the South-to-North Water Diversion Project was selected as the research object. A complex modeling and numerical simulation on embankment stability with regard to the blasting power of the tunnel was conducted using the professional finite difference software FLAC3D to disclose the relationships between the blasting seismic waves with vibration velocity and embankment displacement under different excavation steps. Calculation results demonstrated that displacement generally attenuated from the tunnel wall to the internal structure of rocks under the effect of blasting seismic waves. The tunnel wall was in tension, and tensile stress gradually transformed into compressive stress with increased depth into the rocks. The curtain-grouting zone was mainly concentrated in the compressive zones. For different excavation steps, the vibration velocity at different feature points was high at the beginning of blasting and then gradually decreased. The resultant displacement was relatively small in the early excavation period and slowly increased as blasting progressed. The effects of different excavation steps on the safety of surrounding rocks and embankment under blasting seismic waves were simulated. We found that the blasting-induced vibration velocity was within the safe range of the code and that the calculated displacement was within the allowed range. Numerical simulation was feasible to assess the safety and stability of engineering projects.
Highlights
Borehole-blasting method is widely applied in tunnel construction
We found that the blasting-induced vibration velocity was within the safe range of the code and that the calculated displacement was within the allowed range
On the basis of elastic stress wave theory, Blair and Jiang [2] investigated the propagation law on blasting seismic waves during vertical column charge explosion under elasto-plastic conditions. They concluded that the surface vibration intensity in regions far from the explosive source increased with the increase of detonation velocity, whereas the surface vibration intensity in regions close to the explosive source increased to a critical value first and gradually decreased
Summary
Borehole-blasting method is widely applied in tunnel construction. The advantages of this method are simple operation and low cost. Apart from theoretical analysis and experimental test, Valliappan and Ang analyzed the effects of blasting excavation in underground tunnels on lower architectural and overground structures. They concluded that the generated high-intensity seismic waves from blasting excavation of underground tunnels generated outstanding amplitudes when they were propagated on the surface of rocks. Current studies mainly focus on propagation laws of blasting seismic waves in road tunnels, subways, and effects of blasting excavation on surrounding rocks of underground tunnels by numerical simulation, field monitoring, and so on. A numerical simulation based on the blasting in a tunnel that runs through the Yellow River was conducted to investigate the influences of blasting on the stability of surrounding rocks and embankment
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