Abstract
As the shield section passes through the silt-rock strata, the rock stratum of the tunnel section has to be blasted into blocks in advance, and the diameter of the blocks should be less than 30 cm after breaking, and then, the blocks could smoothly enter the soil cabin through the opening of the tunnel boring machine (TBM) cutter head and finally be discharged through the screw machine. The geology of rock blasting in silt-rock strata is complex, and the vibrations caused by blasting threaten the safety of buildings around the blasting area. According to the measured data of blasting vibrations at the sites, the waveform duration of vibration acceleration and the distribution characteristics of dominant frequency of vibration velocity were analyzed, the energy characteristics of vibration velocity were researched by wavelet analysis, and the attenuation laws of vibration velocity were studied by dimensional analysis (DA). The dominant frequency bands of vibration energy of ground are in the range of 0–15.625 Hz, and the distribution characteristics of frequency bands of vibration energy in different directions of the ground are similar to each other, but the energy magnitude is different from each other. The research results could provide a reference for the safe blasting distance of buildings under similar geological conditions.
Highlights
With the fast economic growth in China, the demand for urban underground space engineering is growing rapidly
In the construction of metro tunnel shield method, the silt-rock strata often encounter in the range of section, such as Shenzhen Metro Line 11 [2], Xiamen Metro Line 2 [3], Shenzhen Metro Line 5 [4], and Fuzhou Metro Line 1 [5], and when the shield machine passes through the silt-rock strata, the rock stratum in the lower part is not easy to break, while the silt stratum in the upper part is easy to enter into the soil cabin, especially the silt stratum, which is rich in groundwater
At 10 : 00 am on April 10, 2016, the dominant frequency of the blasting vibration velocity is between 30 and 70 Hz during the third blasting, and the analysis shows that the structural strength of the silt has been restored due to 10 days from the last blasting
Summary
With the fast economic growth in China, the demand for urban underground space engineering is growing rapidly. Ey concluded that when the rock stratum of the tunnel section was blasted into blocks in advance, and the diameter of the blocks should be less than 30 cm after breaking, the blocks could smoothly enter the soil cabin through the opening of the TBM cutter head and be discharged through the screw machine. As the shield section passes through the silt-rock strata, the rock stratum of the tunnel section has to be blasted into blocks in advance, and the diameter of the blocks should be less than 30 cm after breaking, and the blocks could smoothly enter the soil cabin through the opening of the cutter head and be discharged through the screw machine.
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