| With the rapid development of infrastructure construction in China,maj or construction projects such as transportation,water conservancy and hydropower have ushered in new opportunities for development,which greatly promotes the construction of deep and long tunnels.A large number of deep and long tunnel projects are or will be constructed in mountainous and karst areas with complex topography and geology.The underground environment with strong water-rich,high pressure or ground stress is easy to induce serious water inrush disaster.The reason why the water inrush disaster is difficult to contain is that the complex dynamic catastrophe evolution mechanism is not clear and the traditional monitoring technology and early warning methods are difficult to achieve effective active disaster prevention and control.This paper focuses on the topic of microseismic(MS)monitoring technology and early warning method of tunnel inrush water disaster.The MS response of the two typical inrush water disasters is a key scientific problem.The author has carried out research on acoustic emission/MS monitoring,effective information extraction,disaster status identification and disaster early warning.The following results are obtained through case summary analysis,laboratory testing,software development and other methods.(1)The author first carries out relevant research on the occurrence environment of inrush water disaster.The identification methods of water-filled fracture zone and water-filled mudstone karst are expounded respectively.Furthermore,the pregnancy disaster models of these two typical disaster-causing structures are analyzed.The characteristics of the three factors of release conditions,water storage conditions and induced conditions on water inrush disaster are revealed.On the basis of the difference analysis of focal mechanism between rock burst and water inrush,the relationship between MS monitoring of rock burst and water inrush disaster are established.Based on the comparative analysis of the differences in the focal mechanism of rock burst and inrush water disasters,the connection between two types of disaster MS monitoring is established.The focal mechanism of two typical types of inrush water disasters has been proposed.Combined with the experience of tunnel construction,the water inrush MS monitoring problems on the site are discussed.Traditional MS equipment should be upgraded from three aspects:software,hardware and technology.It provides a new idea for the effective MS monitoring of water inrush disaster in tunnels.(2)The weakening mechanism of water to total input energy and elastic energy storage is revealed,the acoustic emission(AE)precursor characteristic of rock failure is proposed,through the laboratory test of saturated and natural rock under uniaxial compression.Taking the MS monitoring information of high-pressure hydraulic fracture of rock-like materials as samples,the main frequency range of effective signals is revealed.The concept of the MS impact event for characterizing the evolution of time and energy of MS events is proposed.The warning thresholds of the frequency and energy density of MS impact events under the failure of water inrush channel are proposed,which provides a reference for the MS monitoring and early warning of rock mass progressive damage water inrush disaster.(3)The physical model test restores the activity state of water flow and filling in the flow channel.The waveform and spectrum characteristic of the effective MS signal and the noise MS signal in the water flow channel are summarized.The idea of locating the water inrush channel based on the impact MS signal of the filling block and the channel rock wall is put forward.The wavelet packet decomposition theory is introduced to realize the decomposition of low SNR signal in the frequency domain.The frequency range of various MS signals is determined.The efficient signal extraction method has been proposed.(4)The wavelet packet filtering theory is embedded in the system to realize the extraction of effective MS signals.The improved STL/LTA algorithm is embedded in the system,which greatly improves the picking accuracy of the source first arrival.A four-element planar MS monitoring method adapted to the tunnel engineering environment has been proposed.This method realizes the accurate calculation of the source and avoids the ill-conditioned problem of solving objective equations.Based on the Matlab language the MS information analysis software is developed,which sets the functions of signal reading,filtering,first arrival pick-up and source location.The analysis software has been successfully applied in the analysis of test data.(5)Based on the whole process evolution information of the two typical water inrush disasters,the fusion analysis and early warning method of multiple information in water inrush disaster is established.A comprehensive analysis method for the whole process of catastrophe based on principal component analysis and functional situation is established.A comprehensive evaluation model for multi-parameters of inrush water disasters is established,and the inrush water disasters are divided into four stages:calm period,development period,mutation period and late stage.Based on the energy theory the probability of the occurrence of water inrush disaster at any time is determined.(6)Based on the construction activities of the Letuan tunnel on the Binlai expressway,the MS signal waveform and spectrum characteristics of the background noise,blasting operation,anchor spray work,rock drilling work,water spraying and suspected water inrush channel failure are revealed.The MS monitoring signal generated by tunnel production activities provide sample support for data interpretation and stripping of invalid information. |
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