关键词: 分岔隧道, 小间距, 爆破监测, 动力特性, 频谱分析

Abstract: Bifurcation tunnel is one of the new types tunnels. Taking the project of Qishucao bifurcation as the background, the field experiments of vibration effects of rock masses in tunneling blasting have been done. Based on the measurement of waveforms of the vibration velocity in different distances away from the tunneling blasting sources in the working face of adjacent tunnel, blasting vibration analysis of concrete lining tunnel is described by analyzing the peak particle velocity and its main frequency, especially for the blasting dynamic characteristics of mid-board and its vibration velocity variation. The results of the tests and analysis show that: (1) the near-blast side of old tunnel is the strongest vibration zone and the radial vibration is the highest which has a regular varying character along the mid-board; (2) the seismic effect of cutting hole blasting is the most intensive and its intensity is about two times greater than that of the other two blast-holes blasting; (3) the main vibration frequency of concrete lining is mostly low frequency from 20 Hz to 95 Hz, the higher frequency is absorbed quickly. (4) the peak vibration velocity always appears at the vault or in the middle of the mid-board in the same testing cross-section of the old tunnel; the Sadoy ’s formula is not reasonable for the vibration prediction of particle vibration near the blasting face. In light of construction characteristics of the adjacent blasting, the control measures of blasting vibration are proposed; the presented research achievements have better applied to practical project; and satisfactory results are obtained.

Key words: bifurcation tunnel, adjacent tunnels, blasting monitoring, dynamic characteristics, spectrum analysis