| With the implementation of the strategy of strong transportation network and comprehensive three-dimensional transportation network planning outline,the demand for urban underground engineering construction in my country continues to rise.The Tunnel Boring Machine(TBM)has the characteristics of fast and high efficiency and is widely used in the construction of urban underground space.However,urban tunnel boring machines are faced with abnormal geological disasters such as fault fracture zones,karst caves,and composite stratum,which cause disasters such as water inrush,landslides,road collapse,and surface buildings overturning,frequently.Therefore,to improve the safety and stability of the TBM passing through the unfavorable geological area,it is particularly important to carry out the advance geological prospecting during the construction of the TBMs.The seismic wave is sensitive to interface information such as fault fracture zones,karst caves,and composite strata.It has become the mainstream method for advanced geological forecasting of tunnels.However,the frequency of seismic wave method is low and insufficient detection accuracy.It mainly solves the detection of large-scale disaster-causing structures,and it is easy to miss meter-level to sub-meter-level disaster structures.Therefore,traditional seismic wave detection methods cannot meet the needs of urban tunnel detection.Fortunately,the array sonic wave ahead prospecting(ASAP)with the innovative idea of"high-frequency sonic waves+array observation" is expected to solve the problem of fine detection of abnormal geological bodies.Sonic waves have the following characteristics high frequency,short wavelength and high resolution;Due to the high frequency of sonar,the wavelength is short.The array observation overcomes the diffusion effect of the wave field,the observation is more adequate.By fully combining the advantages of the above,the forward energy can be more focused and better resolution can be obtained.However,different with the sonic environments,the practical application of this method in TBM tunnel construction faces the following problems:1)The location of the TBM cutter head for carrying probes is limited,so how to achieve full observation of wave field information under the condition of a small number of probes;2)The noise in tunnel is strong,how to suppress the noise and improve the signal-to-noise ratio(S/N)of observation data;3)The rock mass in front of the roadheader is disturbed by the tunneling of the cutter head.When the high-frequency sound waves pass through the disturbed area,imaging accuracy caused by signal phase distortion.How to consider the distortion effect to build a fine detection imaging method.Therefore,it is urgent to carry out the design of fine detection and observation system,sonic data denoising and fine imaging of TBM,to realize the advanced geological fine detection of TBM construction array acoustic wave for meter sub meter disaster sources.Therefore,it is necessary to carry out the design of fine detection and observation system,denoising and fine imaging of TBM.To realize the advanced geological fine detection of TBM construction array acoustic wave for meter sub meter disaster sources.Realize the advanced geological and fine detection of TBM using ASAP.In order to solve the problem of ASAP,this paper uses theoretical analysis,numerical simulation,physical model experiment and field test to prove the correctness of this method.A method of "high-frequency sonic wave and array observation" is proposed for ASAP.The sparse observation system,structure complexity-guided predictive filtering(SCG—PF),and fine imaging method were carried out respectively.In addition,the imaging features and detection resolution capabilities are summarized to verify the effectiveness and applicability of this method,which provides theoretical basis and guarantee for the processing of field data of ASAP.On this basis,ASAP prototype was developed.A complete set of methods,software,and instrument systems for advanced geological fine detection of TBM using ASAP were formed and tested.The main research contents and achievements are as follows:(1)Sufficient observation of wavefield information under the condition of sparse probe observation.Aiming at the requirement of realizing sufficient perception of wave field information under the sparse observation of a small number of probes,this paper determines the initial observation position based on the resolution requirement of fine detection,and refers to the evaluation method of observation system in the field of oil and gas exploration,it proposes an array sonic wave radiation pattern suitable for tunnel detection.The observation position,combined with the characteristics of the cutter head rotation,proposes a full coverage-based array observation evaluation criterion,and realizes the sparse optimization of the probe;It realizes sufficient observation of reflected signals and provides sufficient observation data for subsequent array signal processing.(2)Noise removal method of TBM with strong spatio-temporal difference.In view of the strong noise interference of urban TBM construction tunnels and the lack of TBM data processing methods.Firstly,based on the noise of the measured data of the tunnel,the data shows strong spatio-temporal differences in the time domain and frequency domain.The removal strategy of un-stationary noise with strong spatial difference,focusing on the removal of un-stationary data noise.The method takes the local structural features as prior information,constructs an adaptive factor guided by the complexity of the local structure.Finally,adaptively selects the filtering factor for different locations according to the difference in the spatiotemporal structure of the data.The constrained auto-regression(AR)model inversion method removes noise,improves the signal-to-noise ratio(S/N)of the ASAP data.It lays the foundation for further accurate imaging of abnormal body of TBM.(3)The wave velocity calculation method of abnormal geological body reflection matrix distortion correction.The wave field of high-frequency sonic wave will be distorted when it passes through the disturbed area of cutter head excavation.The more accurate acquisition of wave velocity information of conductive underground medium is the prerequisite for achieving fine imaging.The imaging accuracy is insufficient,and the wave velocity estimation is inaccurate.In this manuscript,the sonic wave phase distortion correction method based on projection transformation is first constructed to correct the reflection matrix distortion caused by high-frequency acoustic wave passing through the cutter head excavation disturbance area.Based on the width of the main diagonal of the reflection matrix reflecting the accuracy of wave velocity,the velocity spectrum analysis method of Radon transformation is proposed.The wave velocity of rock mass can be obtained accurately.(4)Time reversal fine imaging method based on azimuth scanning.Aiming at the problem of insufficient imaging accuracy caused by the mutual influence of signals caused by the proximity of several meter level and sub meter level unfavorable geological bodies.This manuscript introduces the azimuth scanning method based on the received data,the pseudo spectral energy function of the acoustic signal,and constructs the Green’s function of azimuth information correction with the scanning direction as the constraint to solve the response of the acoustic signal.On this basis,using the covariance matrix of the reflected signal,a fine imaging method of abnormal geological bodies containing time reversal operator is constructed to achieve fine imaging of meters to sub meters of bad geological bodies.Based on the above research,the ASAP equipment of TBM is developed,and the field test is carried out in Zhangmatun Iron Mine of Jinan and Jiaozhou Bay second submarine tunnel.The detection results are basically consistent with the actual distribution,which verifies the effectiveness and applicability of the method. |
PDF Full Text Request