不同类型岩爆孕育过程中震源体积自相似分布的分形特征分析
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摘要
岩爆严重威胁着深部岩体隧洞的施工安全,并造成大量的人员伤亡及财产损失。在深部岩体隧洞岩爆灾害的孕育及发生过程经常伴随一系列的微震事件;通过针对微震事件发生的时间、空间位置、数量多少、能量大小及震源体积分布等特征参数进行分析,有助于认识岩体的破裂机制,进而为岩爆等动力地质灾害的研究与防治提供理论基础。采用理论分析与微震监测相结合的研究手段,基于锦屏Ⅱ级水电站深埋引水隧洞施工过程中大量不同类型(即时性应变–结构面滑移型岩爆、即时性应变型岩爆)、不同等级即时性岩爆的典型案例,针对岩爆孕育及发生的动态过程展开震源体积分布的自相似特征及分形行为研究。结果表明:深部岩体隧洞开挖即时性岩爆孕育过程中的微震源体积分布表现出良好的自相似性,其自相似系数均大于0.97;对于不同类型的即时性岩爆,其微震信息震源体积分形维数均随着岩爆孕育过程不断增加,岩爆发生时达到最大值的特征;应变–结构面滑移型岩爆过程中每天的震源体积分形维数分布在0.1～0.8范围内,应变型岩爆过程中每天的震源体积分形维数分布在0.4～1.3范围内,岩爆发生当天的分形维数均大于1.0。研究成果对高地应力条件下岩爆灾害动态预警体系的建立具有重要的指导意义,同时可为中国深部岩体隧洞开挖过程的安全设计提供必要的科学依据和支撑。
Rock-burst is a serious threat to the construction safety of deep tunnels, which causes huge economic loss and staff casualties. The evolution process of rock-bursts is accompanied by a series of micro-seismic events. Analyzing and processing these characteristic parameters about the microfracturing such as size, time, space, energy, volume, etc, which is helpful to understand the fracture mechanism of rock mass, and provides a theoretical basis for the study of rock-burst disaster. In this research, theoretical analysis combined with micro-seismic monitoring were used. Based on the hundreds of immediate rock-bursts(including immediate strain structure slip rock-bursts and immediate strain rock-bursts),with different types and intensities, occurred in four deep headrace tunnels at Jinping-Ⅱ hydropower station in Sichuan province, China. The selfsimilarity characteristic and fractal behavior of micro-seismic volume distributions during the dynamic evolution process of such rock-bursts were studied. The achieved results are as follows: The volume distribution of micro-seismic events during the development of immediate rock-bursts shows great self-similarity, the value of correlation coefficient are all greater than 0.97. For different types of immediate rock-bursts, the daily volume fractal dimension increases during the evolution of immediate rock-bursts, and they totally increase up to a certain threshold value before the rock-burst occur. The volume fractal dimension values on each day were between 0.8 and 0.1 for the evolution of immediate strain structure slip rock-bursts, but those of immediate strain rock-bursts were between 0.4 and 1.3, and both of them are greater than 1.0 when the rock bursts.The micro-seismic energy fractal dimension can be used as a significant guideline to build up a warning system and reduce the risk of rock-bursts during construction under high in-situ stress condition.
Rock-burst is a serious threat to the construction safety of deep tunnels, which causes huge economic loss and staff casualties. The evolution process of rock-bursts is accompanied by a series of micro-seismic events. Analyzing and processing these characteristic parameters about the microfracturing such as size, time, space, energy, volume, etc, which is helpful to understand the fracture mechanism of rock mass, and provides a theoretical basis for the study of rock-burst disaster. In this research, theoretical analysis combined with micro-seismic monitoring were used. Based on the hundreds of immediate rock-bursts(including immediate strain structure slip rock-bursts and immediate strain rock-bursts),with different types and intensities, occurred in four deep headrace tunnels at Jinping-Ⅱ hydropower station in Sichuan province, China. The selfsimilarity characteristic and fractal behavior of micro-seismic volume distributions during the dynamic evolution process of such rock-bursts were studied. The achieved results are as follows: The volume distribution of micro-seismic events during the development of immediate rock-bursts shows great self-similarity, the value of correlation coefficient are all greater than 0.97. For different types of immediate rock-bursts, the daily volume fractal dimension increases during the evolution of immediate rock-bursts, and they totally increase up to a certain threshold value before the rock-burst occur. The volume fractal dimension values on each day were between 0.8 and 0.1 for the evolution of immediate strain structure slip rock-bursts, but those of immediate strain rock-bursts were between 0.4 and 1.3, and both of them are greater than 1.0 when the rock bursts.The micro-seismic energy fractal dimension can be used as a significant guideline to build up a warning system and reduce the risk of rock-bursts during construction under high in-situ stress condition.
引文
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[13]Chen Bingrui,Feng Xiating,Zeng Xionghui,et al.Real-time micro-seismic monitoring and its characteristic analysis during TBM tunneling in deep-buried tunnel[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(2):275-283.[陈炳瑞,冯夏庭,曾雄辉,等.深埋隧洞TBM掘进微震实时监测与特征分析[J].岩石力学与工程学报,2011,30(2):275-283.]
[14]Mendecki A J.Principles of monitoring seismic rockmass response to mining[C]//Rock-bursts and Seismicity in Mines.Rotterdam:Balkema,1997:69-79.
[15]Feng Xiating,Chen Bingrui,Ming Huajun,et al.Evolution law and mechanism of rock-bursts in deep tunnels:Immediate rock-burst[J].Chinese Journal of Rock Mechanics and Engineering,2012,10(3):447-451.[冯夏庭,陈炳瑞,明华军,等.深埋隧洞岩爆孕育规律与机制:即时型岩爆[J].岩石力学与工程学报,2012,10(3):447-451.]
[16]Yu Yang,Feng Xiating,Chen Bingrui,et al.Analysis of energy fractal and microseismic information characteristics about immediate rockbursts in deep tunnels with different excavation methods[J].Rock and Soil Mechaninics,2013,34(9):2622-2628.[于洋,冯夏庭,陈炳瑞,等.深埋隧洞不同开挖方式下即时型岩爆微震信息特征及能量分形研究[J].岩土力学,2013,34(9):2622-2628.]
[17]Feng Xiating,Yu Yang,Feng Guangliang,et al.Fractal behaviour of the microseismic energy associated with immediate rockbursts in deep,hard rock tunnels[J].Tunnelling and Underground Space Technology,2016,51:98-107.
[2]Mandelbrot B B,Passoja D E,Paullay A J.Fractal character of fracture surfaces of metals[J].Nature,1984,308:721-722.
[3]Sadovskiy M A,Golubeva T V,Pisarenko V F,et al.Characteristic rock dimensions and hierarchical properties of seismicity[J].Earth Phys,1984,20:87-96.
[4]Xie Heping,Pariseau W G.Fractal character and mechanism of rock bursts[J].International Journal of Rock Mechanics and Mining Sciences,1993,30(4):343-350.
[5]Kagan Y Y,Knopoff L.Stochastic synthesis of earthquake catalogs[J].Geophys Royal Economic Society,1981,86(B4):2853-2862.
[6]Kagan Y Y,Knopoff L.Statistical study of the occurrence of shallow earthquakes[J].Geophys Royal Economic Society,1978,55(1):67-86.
[7]Hirata T,Satoh T,Ito K.Fractal structure of spatial distribution microfracturing in rock[J].Geophysical Journal International,1987,90(2):367-374.
[8]Bhattacharya P M,Majumdar R K,Kayal J R.Fractal dimension and b-value mapping in northeast India[J].Current Science,2002,82(12):1486-1491.
[9]冯夏庭,陈炳瑞,张传庆,等.岩爆孕育过程的机制、预警与动态调控[M].北京:科学出版社,2013.
[10]Yu Yang,Feng Xiating,Chen Bingrui,et al.The micro-seismic volume fractal characteristics research for different types of immediate rock-bursts in deep tunnels[J].Chinese Journal of Geotechnical Engineering,2017,39(12):2173-2179.[于洋,冯夏庭,陈炳瑞,等.深部岩体隧洞即时型岩爆微震震源体积的分形特征研究[J].岩土工程学报,2017,39(12):2173-2179.]
[11]Li S J,Feng X T,Li Z H,et al.In situ monitoring of rockburst nucleation and evolution in the deeply buried tunnels of JinpingⅡhydropower station[J].Engineering Geology,2012,137/138:85-96.
[12]Jiang Quan,Feng Xiating,Zhou Hui,et al.Study on acceptable minimum interval of long deep-buried hydropower tunnels in Jinping hydropower station[J].Chinese Journal of Rock Mechanics and Engineering,2008,29(3):656-662.[江权,冯夏庭,周辉,等.锦屏Ⅱ级水电站深埋引水隧洞群允许最小间距研究[J].岩土力学,2008,29(3):656-662.]
[13]Chen Bingrui,Feng Xiating,Zeng Xionghui,et al.Real-time micro-seismic monitoring and its characteristic analysis during TBM tunneling in deep-buried tunnel[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(2):275-283.[陈炳瑞,冯夏庭,曾雄辉,等.深埋隧洞TBM掘进微震实时监测与特征分析[J].岩石力学与工程学报,2011,30(2):275-283.]
[14]Mendecki A J.Principles of monitoring seismic rockmass response to mining[C]//Rock-bursts and Seismicity in Mines.Rotterdam:Balkema,1997:69-79.
[15]Feng Xiating,Chen Bingrui,Ming Huajun,et al.Evolution law and mechanism of rock-bursts in deep tunnels:Immediate rock-burst[J].Chinese Journal of Rock Mechanics and Engineering,2012,10(3):447-451.[冯夏庭,陈炳瑞,明华军,等.深埋隧洞岩爆孕育规律与机制:即时型岩爆[J].岩石力学与工程学报,2012,10(3):447-451.]
[16]Yu Yang,Feng Xiating,Chen Bingrui,et al.Analysis of energy fractal and microseismic information characteristics about immediate rockbursts in deep tunnels with different excavation methods[J].Rock and Soil Mechaninics,2013,34(9):2622-2628.[于洋,冯夏庭,陈炳瑞,等.深埋隧洞不同开挖方式下即时型岩爆微震信息特征及能量分形研究[J].岩土力学,2013,34(9):2622-2628.]
[17]Feng Xiating,Yu Yang,Feng Guangliang,et al.Fractal behaviour of the microseismic energy associated with immediate rockbursts in deep,hard rock tunnels[J].Tunnelling and Underground Space Technology,2016,51:98-107.
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