| With the increasing national comprehensive strength and the continuous promotion of infrastructure construction,the construction of major underground projects in municipalities,transportation,water conservancy and hydropower has entered a stage of rapid development.In the southwestern mountainous and densely populated urban areas,where the geological and engineering environment is ultra complex,a large number of tunnels are under construction.It is inevitable to encounter unfavorable geological bodies,such as fault and broken zones,weak interlayers,fissures,caves,underground dark rivers,etc.,when some tunnels are built in complex geological conditions,resulting in water inrush,mud inrush,collapse,tunnel deformation and other disasters,which seriously threaten the safety of construction workers and the normal tunneling.The utility of advanced geological detection technology to identify the characteristics of unfavorable geological bodies in front of the tunnel face is particularly important to avoid these accidents.The tunnel seismic advanced geological detection technology has been verified by practical engineering.It is an effective technology to detect the unfavorable geological bodies in front of the tunnel face,and has the advantages of a long prediction range and high detection accurance.However,the market for tunnel seismic advanced geological detection instruments in China is mainly occupied by foreign manufacturers,and the following limitations still exist in the detection techniques,instruments and data processing methods used: 1)In the existing tunnel seismic advanced geological detection technology,additional holes are drilled on the sidewall of the tunnel to excite the source of seismic for advanced geological detection during the stagnation of tunnel construction,affecting the continuity of tunnel construction and has safety hazards.Moreover,the technology has high requirements for operators and technology.2)The commonly used instruments realize the trigger circuit powering and blaster pulse by the connection between the source and the collection instrument.It is easy to have problems of the jumping channel and delay channels,and the operation is complicated and timeconsuming,which leads to the lower data collection efficiency and automation,and the longer forecast.3)The main tunnel seismic data processing mainly adopts twodimensional single-component migration imaging,with insufficient of multi-component data utilization,which leads to the low accuracy of the migration imaging.In view of the above-mentioned problems,literature research,theoretical analysis,numerical simulation,laboratory experimental,field experimental,and other methods are used in this thesis.The forward modeling theory of tunnel seismic full wavefield is studied and a seismic advanced geological detection method based on blast source excitation on tunnel face is proposed.The instrument and software development of the tunnel seismic advanced geological detection based on blast source excitation on tunnel face are completed,and the engineering applicability of the proposed method and the developed instrument is verified through the tunnel field experiment.The following summarizes the main research contents and innovative accomplishments of this thesis:(1)The seismic advanced geological detection method based on blast source excitation on tunnel face is proposed.The existing holes or advanced boreholes on the tunnel face are rationally used to place the source,without interfering with the tunnel construction.On the tunnel wall are the geophones arranged.The internet of things technology is used to realize the data automatic collection,storage,transmission,and analysis.Through the interpretation of the supporting software,the adverse geological body and its spatial relationship with the tunnel structure can be visually displayed in the three-dimensional(3D)tunnel geological mode.The proposed method can realize continuous and real-time advanced geological detection and significantly improve the efficiency and accuracy of tunnel seismic advanced geological detection.(2)The miniaturized and intelligent instrument for seismic advanced geological exploration based on the blast source excitation of the tunnel face is developed.The instrument integrates the functions of the trigger,data collection,conversion,transmission,power supply,and other functions on the geophone,which mainly includes five parts: source and trigger system,data collection system,data processing system,data transmission system,and auxiliary system.Compared with the mainstream seismic advanced geological detection instruments in the market,it simplifies the equipment links and operation process,and has the advantages of high use efficiency,good reliability and low cost,which can better meet the needs of tunnel seismic advance geological detection instruments in China.(3)This thesis develops the tunnel seismic 3D-3C three-component(3C)reverse time migration(RTM)imaging in order to address the issue of the low precision of existing migration imaging.The following benefits of tunnel seismic 3D-3C RTM imaging over comparable migration imaging techniques:(1)It successfully overcomes the effect of small offset and extends the range of migration imaging.(2)It can realize multi-component data migration imaging and improve the energy of anomalous interface.(3)It can better use multiple waves and improve the resolution of the anomalous interface. |
