Propagation characteristics of vibration waves induced in surrounding rock by tunneling blasting

Advances in Civil Engineering

Gao

2020

The blasting vibration signal obtained from tunnel construction monitoring is affected by the external environment, which contains a lot of noise that causes distortion during signal processing. To analyse the blasting vibration signal and determine the appropriate water seal blasting charge structure for construction, combined with wavelet threshold denoising method and HHT transformation, the blasting vibration signals of the four charge structures of conventional charge, water interval charge at both ends, water interval charge at the orifice, and water interval charge at the hole bottom are denoised and HHT is analysed. The results show that the wavelet threshold method can effectively eliminate high-frequency noise in the blasting vibration signals and retain information carried by the vibration signal itself. The frequency and energy of the blasting vibration signals of the water interval charge at both ends are densely distributed in the range of 0 s to 0.9 s and below 100 Hz. The frequency and energy of the blasting signals of the other three charging structures are reduced within the same range, sparse areas appear, and the instantaneous total energy is smaller than that with a water interval charge at both ends, which shows that the water interval charge at both ends can effectively apply explosive energy to the surrounding rock and reduce energy loss in the explosive. The blasting vibration signal energy of the water interval charge at both ends is mainly concentrated in components IMF2 to IMF5, and the corresponding frequencies are concentrated at 6 Hz to 11 Hz and 20 Hz to 70 Hz, while the blasting vibration signal energy of other three charge structures is mainly distributed in components IMF2 to IMF4, corresponding frequencies are concentrated within 20 Hz to 70 Hz, and the distribution at low frequencies is not obvious. Therefore, when using the water interval charge at both ends, it is necessary to increase the main vibration frequency of the original vibration signals by reducing the single section charge and using frequency shift technology to avoid the natural frequency of the structure and reduce resonance-induced damage.

Section: Introductionmentioning

confidence: 99%

Vibration Signal Analysis of Water Seal Blasting Based on Wavelet Threshold Denoising and HHT Transformation

Advances in Civil Engineering

Gao

2020

“…e results show that the maximum main stress decreases with the increase in the distance from the source. Chen et al [15] used the separation variable method to solve the displacement potential function of blasting vibration wave propagation and obtained the variation law of particle movement and stress with axial distance, radial distance, and time in the surrounding rock.…”

Section: Introductionmentioning

confidence: 99%

Optimization Analysis of Controlled Blasting for Passing through Houses at Close Range in Super‐Large Section Tunnels

Song

Mao

Tian

et al. 2019

Shock and Vibration

According to the on-site vibration velocity monitoring and peak vibration velocity prediction, it is found that the maximum vibration velocity generated by the existing Dizong blasting scheme does not meet the requirements of the maximum allowable vibration velocity of houses. Therefore, the existing blasting scheme is optimized by reducing the maximum single-segment charge and a variety of damping measures such as multistage duplex wedge groove, adding damping hole, and millisecond blasting. In addition, the blasting data before and after optimization are analyzed and compared by wavelet (packet) technology. The results show that the optimized blasting main frequency domain is increased to 50∼150 Hz and the maximum vibration intensity value is reduced by 79.8%. Based on the time-energy analysis, the maximum energy value is reduced by 67.75% compared with the original scheme, and the dominant energy of the original scheme is reduced by 97.81%, 71.49%, 82.44%, 95.93%, and 93.03%, respectively, after optimization. The maximum vibration velocity generated by the optimized blasting scheme construction is 1.12 cm/s, which is less than the maximum allowable vibration velocity of the building of 1.2 cm/s, which meets the maximum allowable vibration velocity requirements of the building. The optimized blasting scheme realizes the safe and rapid construction of the two steps of the Dizong tunnel, which can provide a reference for similar engineering construction in the future.

“…Yue et al [2] studied crack propagation in PMMA material with double holes under the directional controlled blasting. Chen et al [3,4] investigated the propagation characteristics of vibration waves induced in surrounding rock by tunneling blasting. By using the blasting technique, Verma et al [5] studied the blasting damage of a large-scale rock mass quality with a fault tunnel, and the results were verified by the ultrasonic testing of core samples obtained from a tunnel site experiment.…”

Section: Introductionmentioning

confidence: 99%

Study on the Fracture Behavior of Cracks Emanating from Tunnel Spandrel under Blasting Loads by Using TMCSC Specimens

Zhu

et al. 2019

Shock and Vibration

Radial cracks may exist around tunnel edge, and these cracks may propagate and weaken tunnel stability under nearby blasting operations. In order to study the blast-induced fracture behavior of radial cracks emanating from a tunnel spandrel, a tunnel model containing a spandrel crack (TMCSC) with different inclination angles was proposed in this paper. Crack propagation gauges (CPGs) and strain gauges were used in the experiments to measure crack initiation moment and propagation time. Finite difference models were established by using AUTODYN code to simulate crack propagation behavior and propagation path. ABAQUS code was used to calculate dynamic stress intensity factors (SIFs). The results show that (1) crack inclination angles affect crack initiation angles and crack propagation lengths significantly; (2) critical SIFs of both mode I and mode II decrease gradually with the increase of the crack propagation speed; (3) the dynamic energy release rates vary during crack propagation; and (4) there are “crack arrest points” on the crack propagation paths in which the crack propagation speed is very small.