Abstract
Blasting excavation is extensively used in tunnel construction, and the adverse effect of ground vibration induced by blasting on surrounding structures and inhabitants is a critical problem. This study aims to investigate the tunnel hollow effect on triaxial peak particle velocities (PPV) and dominant frequencies induced by electronic detonator. Field experiments were conducted in a shallow tunnel construction site and the ground vibration waveforms were recorded. Variational mode decomposition (VMD) was applied to denoise and correct the zero-drift phenomenon, and the proposed method of selecting the optimal parameter was verified. A series of statistical analyses and tests were performed to evaluate the differences of peak particle velocity and dominant frequency among various monitoring points. The results showed that the hollow effect on Z-axis PPV is significant, and triaxial PPV is also affected when the horizontal distance exceeds 30 m. The hollow effect on dominant frequency could not be identified since the hollow of tunnel is a free face, and the dominant frequency of reflected wave remains unchanged. An augmented factor of 1.229 is determined carefully as the hollow effect factor on PPV. Therefore, blasting vibration induced by electronic detonator of the excavated zone should be attached with greater importance, and hollow effect on PPV should be considered in the blasting design of tunnel excavation.
Highlights
With the economy development and urbanization acceleration in China, underground space utilization has grown rapidly
Signal Decomposition by Variational Mode Decomposition (VMD). e measured vibration signals usually contain noises, and the zero-drift phenomenon might occur; denoising and zero-drift correction is required in most cases
Variational mode decomposition (VMD) was first proposed by Dragomiretskiy and Zosso [24], the thought of which is to decompose an input signal f0 into a series of subsignals, namely, intrinsic mode functions (IMF) um, which have sparsity properties while still could reproduce the input. e sparsity of each mode is defined as its bandwidth in the spectral domain, and VMD assumes that each mode m is compact around a center pulsation wm
Summary
With the economy development and urbanization acceleration in China, underground space utilization has grown rapidly. Studies show that only up to 30% of blasting energy is directly applied to rock fragmentation. The rest energy may cause adverse effects such as ground vibration, flying rocks, noise, and air blasts [1]. Among the above side effects of blasting, ground vibration has long been considered as the primary problem since its amplitude, dominant frequency, and duration might cause damage to nearby structures and nuisance to inhabitants [2]. In general, can be measured as ground displacement, acceleration, and velocity. Peak particle velocity (PPV) is used to assess the amplitude of ground vibration, and many regulations are designed based on PPV and dominant frequency [3, 4]
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