Blast Vibration Control in A Hydropower Station for the Safety of Adjacent Structure

Abstract

The transverse cofferdam in Xiangjiaba hydropower station was a water retaining concrete structure with a length of 126 m, a width of 12 m, and a height of 25.2 m, consisting of masonry, plain concrete structure (PC), and roller compacted concrete (RCC), which had to be demolished by blasting after the dam was built. There were many precise instruments nearby the cofferdam which had strict restrictions on blasting vibration. Therefore, the cofferdam was divided into six blasting regions, including land blasting and underwater blasting. Blasting parameters and blasting network structure were accurately designed and continuously optimized through blast-induced vibration test results. At nine measurement points in different locations, 57 blast vibration data were recorded. Consequently, 1386 holes with an explosive weight of 9641.3 kg were detonated in land blasting. The highest levels of vibration were recorded as 8.74 cm/s in the desilting tunnel on the right of the cofferdam. The explosives up to 11887.7 kg were detonated in an underwater blasting. According to the analysis of the law of vibration attenuation, the blast vibration value was reduced to 7.65 cm/s. The results showed that the research on the attenuation law of blasting vibration can effectively increase the charge weight per delay and control the blast-induced vibration. Consequently, the peak particle velocity (PPV) of underwater blasting could be predicted by analyzing the PPV of land blasting in same structure, which provided the basis for the design of underwater blasting parameters. A reliable method for cofferdam demolition in hydropower station was proposed, which provided a reference for similar projects.

Investigation of Shock Wave Pressure Transmission Patterns and Influencing Factors Caused by Underwater Drilling Blasting

“…A total of 15 field monitoring experiments were conducted (as shown in Table 1), and 45 sets of shock wave pressure data from underwater drilling blasting were obtained for different source distances (8-323 m), explosive weights (6-115 kg), numbers of blastholes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), and water depths (6.2-20.0 m). The field monitoring results showed that the shock wave pressure was in the range of 0.04-12.89 ×10 5 Pa.…”

“…In terms of field monitoring, Tatlısuluo glu et al investigated the engineering characteristics of underwater blast shock waves in offshore waters in Turkey [7]. Ma et al obtained the attenuation pattern of underwater drilling blasting shock waves in rock masses using the underwater blast of a hydropower station as the background [8]. Ge et al provided a semi-theoretical and semi-empirical equation for underwater shock waves using shallow underwater drilling blasting tests on a seashore [9].…”

Digital Processing of Seismic Data from Open-Pit Mining Blasts

“…It is worth mentioning that basic seismic monitoring approaches do not involve natural vibration data from nearby objects, regardless of their effect on total vibration. For example, in [26,29] the measurements were carried out the same way, but the instruments were located at selected points without direct recording of any nearby object's natural vibration. However, additional research on the dominant frequency changes when possible resonance is considered, which may improve the accuracy of the drilling and blasting parameters.…”

“…Blast waves have different characteristics that can be extracted using Fourier transform [27], wavelet transform, and fractal analysis [28][29][30]. The wavelet wave signal decomposition is used to derive the wavelet coefficients.…”

Study on the Propagation Law of Water Hammer Wave in Underwater Blasting and the Reducing Effect of Air Curtain on Water Hammer Wave

“…In the aspect of the propagation law of water hammer wave, Peng [11] derives the vibration frequency prediction formula considering the altitude effect. In addition, Ma et al [12] analyze the peak velocity (PPV) of surface blasting of the same structure and predict the peak velocity of underwater blasting (PPV). Besides, Huang [13] establishes the numerical model of multimaterial arbitrary Lagrangian-Eulerian (MMALE) technique and studies the peak pressure of the explosive underwater explosion.…”