Safety threshold of blasting vibration velocity in foundation excavation of Baihetan super-high arch dam
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ORIGINAL PAPER
Safety threshold of blasting vibration velocity in foundation excavation of Baihetan super-high arch dam Wenjun Xia 1,2 & Wenbo Lu 1,2 & Gaohui Wang 1,2 & Peng Yan 1,2 & Da Liu 1,2 & Zhendong Leng 1,2 Received: 27 July 2019 / Accepted: 10 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Blasting damage control is one of the main problems in the dam foundation excavation of Baihetan Hydropower Station, and it is important to study the relationship between the blasting vibration and blasting damage. In this paper, a horizontal presplit blasting experiment was carried out at the dam foundation. By combining vibration monitoring and sonic wave detection before and after blasting, the corresponding relationship between the peak particle velocity (PPV) and the damage degree was established. On this basis, the function of grouting in the blasting excavation was analyzed. The results indicate that grouting is very helpful for the blasting damage control. After grouting, the P-wave velocity of the rock mass is increased by approximately 20%, the blasting damage depth is reduced by approximately 14%, and the safety threshold of the PPV is increased by approximately 25%. Meanwhile, the safety threshold of the PPV is positively correlated with the P-wave velocity of the rock mass. According to the damage control standard and rock mechanical properties, the blasting parameters can be rationally optimized. Keywords Blasting damage . Peak particle velocity . Safety threshold . Grouting
Introduction Baihetan Hydropower Station is located at the gorge between Ningnan county of Sichuan province and Qiaojia county of Yunnan province in the lower reaches of the Jinsha River, as shown in Fig. 1. It has an installed capacity of 16,000 MW and is another 10 million kilowatt-class hydropower station after the Three Gorges. As an economic and efficient method for rock breaking, blasting is widely used in dam foundation excavation at Baihetan Hydropower Station (Gao et al. 2019). However, a large amount of columnar jointed basalt is distributed at the dam site, which makes the geological conditions complicated and the construction difficult (Fan et al. 2018). Therefore, the blasting scheme must be optimized to control the blasting damage strictly during excavation. During the process of rock formation, in addition to the geological discontinuities between the blocks formed in the * Wenbo Lu [email protected] 1
State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
2
College of Water Resource and Hydropower, Wuhan University, Wuhan 430072, China
incipient stage (Shang et al. 2018), there are also many defects in the blocks, such as holes and cracks, which are called the initial damage. Under the action of blasting stress waves, these cracks are activated and extended, increasing the degree of rock damage and weakening the mechanical properties of the rock mass (Grady and Kipp 1980; Taylor et al. 1986; Yang et al. 1996). Researchers ha
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