TBM Rock-breaking Source Seismic Method And Its Applications For Ahead Geological Prospecting In TBM Construction Tunnel

The TBM construction method has become an important trend and development direction of tunnel construction in China,and it is very likely to dominates the tunneling with the advantages of high speed,high quality,high comprehensive economic efficiency and safe construction.At the same time,complex geological conditions and frequent geological hazards in TBM construction has brought great challenges,which easily leads to abnormal TBM tool wear,cutter damage,affecting the efficiency of tunneling,even TBM blocked,scrapped or casualties and other major accidents.How to prospect the adverse geology ahead the TBM tunnel,which can be pre-developed reasonable measures and construction plans for TBM's safe and efficient tunneling and disaster prevention and control,is extremely important.However,the existing ahead prospecting methods used for TBM construction tunnels are not mature.Thus this has become a recognized problem at home and abroad.The electromagnetic environment for TBM tunneling is complex,and the observation space is narrow,which has increased difficulties for traditional ahead prospecting methods' application.In addition,TBM is of a high degree of mechanization with a fast tunneling speed.This brings a higher demand for the integrated integration and automated real-time detection of the ahead prospecting methods.Frequently,the TBM rock breaking seismic prospecting thoughts provides a good reference for the above problems.This method can detect the geological conditions ahead the tunnel surface during tunneling,without interfering with the construction,and no great transformation of TBM structure.It is suitable for TBM environment,and has good research value and application prospect.Conpared with the traditional active seismic source(such as explosives and hammering,etc.),the vibration caused by TBM rock breaking is unique for its randomness,uncontrollability and time persistence and the original seismic records cannot be directly identified and interpreted.Corresponding research has been made at home and abroad,but not perfect in the following aspects:? At present,the summary and analysis of seismic record reconstruction methods are not comprehensive.The signal to noise ratio of the reconstructed seismic record is low,so this causes difficulties to the recognition and processing of effective reflection information;(2)In the follow-up processing and migration imaging of reconstructed seismic records,the existing research continues to adopt the VSP processing method used in the field of petroleum exploration.This method has not yet introduced the research results in the field of tunnel prospecting and the influence of the particularity and complexity of the tunnel environment on the detection effect are not taken into consideration;(3)There is no forward modeling method of the faulted seismic source suitable for the complicated environment of the TBM tunnel,and there is a lack of theoretical validation of forward modeling and imaging effect of typical adverse geology that TBM may encounter.To solve this problem,theoretical analysis,numerical calculation and field test,are used.This paper focuses on the seismic wave field characteristics and forward modeling method,and the reconstruction methods of seismic records,and the beamforming method of TBM rock breaking.The reconstruction and data beamforming methods of TBM's rock-breaking seismic source record were studied,based on which the study on numerical forward simulation and processing imaging is carried out in typical adverse geology that TBM may encounter in construction.This paper also summarizes the characteristics of its migration imaging,validates the effectiveness and reliability of the proposed method,and provides theoretical support for the interpretation of field detection data.Based on what mentioned above,a procedure with independent property rights is developed,and an entire set of methods including data acquisition,processing and interpretation of TBM rock-breaking seismic wave ahead prospecting.The main research and achievements of this paper are as follows:(1)Characteristics and forward modeling method of TBM rock-breaking seismic field.Compared with the traditional active source(such as explosives and hammering,etc.),the seismic source of TBM rock breaking is of randomness,uncontrollability and time persistence.In this paper,the TBM tunneling seismic source data is obtained by field measurement,and the time-frequency characteristics of the measured rock-breaking data are studied.On this basis,forward modeling is carried out.The continuous random signals of different frequency sine wave are used to simulate the rock breaking of the TBM cutter.Multiple seismic source excites continuous signals at random,and rock-breaking seismic wave signals on interaction are formed.The propagation law of the seismic wave field of the rock breaking is studied by forward modeling,which provides reliable theoretical data for the reconstruction of the data of the subsequent TBM rock fracture.(2)Reconstruction method of seismic record of TBM rock breaking based on the correlation interference.Due to the complexity and unconventional nature of the rock-breaking seismic source,the seismic record cannot be directly processed and explained.In this paper,the reconstruction method of seismic records under the excitation of TBM seismic source is put forward centered on theory that the source signal and the receiver signal interfere with each other.The time domain normalization and frequency domain spectral whitening method for each sensor seismic record are studied,and the noise is suppressed to a certain extent.According to the detection needs,the sensor signals collected continuously for a long time are segmented superimposed according to a certain length of time,to obtain a conventional seismic record similar to that under pulsed source excitation.(3)Beamforming method of TBM rock breaking based on the receiving array.The reconstructed seismic record signal-to-noise ratio is relatively low,which brings great interference to the subsequent data processing.Based on the characteristics of TBM's continuous tunneling during the prospecting process,the beamforming method of the seismic wave field based on the sensor receiving array is studied from the common shot point gather and co-detector point CRP gather.The reconstructed seismic records are delayed and superimposed to realize the forward orientation propagation of the seismic wave field of TBM.The energy of the reflected wave ahead the tunnel face is enhanced and the signal-to-noise ratio of the reconstructed seismic record is improved.(4)Numerical forward modeling and imaging characteristics of TBM rock-breaking seismic source's typical adverse geologies TBM broken seismic source.Based on the conventional seismic wave ahead prospecting method,the data processing and migration imaging of the reconstructed seismic records of the rock-breaking seismic source are studied.In view of the typical geologies that may be encountered during TBM construction,geologic models of the lithologic interface,fault area,karst caves and composite geology are made.The characteristics of migration imaging of typical adverse geologies are analyzed and summarized,which lays the theoretical foundation for the detection of typical adverse geological bodies.On the basis of the above research,a special instrument of TBM rock breaking seismic source is developed.This has been verified in the fourth section of Jilin Yinsong Water Supply Project.The prospecting results are basically consistent with the actual tunneling process.Thus,its effectiveness and reliability are verified.