| The uncertainty of the surrounding rock is encountered in the process of tunnel excavation have a great influence on the safety of construction, in order to reduce the risk in the excavation process and decrease the destruction of adverse geological disaster to personnel and mechanical equipment, geological forecast technology is of great importance and practical value. The application of the seismic waves to geological forecast has some advantages like it has advanced detection distance and the detecting precision meet the needs of the project, and the interference to construction process is small, so it is widely used in practical engineering. However, because of the fact that seismic wave field in the tunnel is much more complex than elsewhere, it is difficult to identified and segregated effectively, it often has multi-solutions for the detection results of different seismic wave observation, it is necessary to make further research into forecast technology. The paper has studied the seismic waves in geological forecast during the excavation of tunnel, the main research work and achievements are as follows:(1) On the basis of summarizing the characteristic of geological forecast using the theory of seismic waves reflection, according to the feature of tunnel engineering, this paper studied and adopted a new technology GPT for geological forecast during tunnel construction. It adopted the scheme of 6 trigger points and 12 holes many times cover and array observation, so improved and perfected wire siting and the method of data acquisition. For the seismic waves and the method of field detecting work, I carried out forward modeling research, and verified the rationality and validity of the method in this paper.For the first order pushed speed-stress transverse isotropic elastic wave equation, the space of 10 order precision crisscross network difference scheme is derived and used. According to the characteristics of tunnel and the situation ahead of working face, the forward modeling seismic wave field condition of the tunnel in the conditions of free boundary, the artificial boundary and the elastic boundary, and the staggered grids difference computation format are system discussed. And compiled MATLAB calculation program, providing theoretical basis and practical computing tools for the forward modeling of seismic waves. Basing on this, the model of geological surrounding rock which is commonly seen in engineering is established, and got the corresponding results of the theory from its forward analysis and calculation, thus it provide theoretical basis for the forecast prediction technology GPT this paper adopted.(2)The paper studied the dynamics and kinematic characteristic of seismic waves in the array observation scheme this paper employed. Through using the algorithm such as f-k direction filter,wave velocity scanning and reflection seismic migration imaging etc. compiled MATLAB calculation program ,tested the correctness of corresponding algorithm, and provided basis of the rationality for improving and enhancing the results of geological forecast.(3) The engineering application research applying the method in this paper. Using the geological forecast technology GPT in this paper, we carried out field test in 3 tunnels, we got the migration imaging results through the analysis and processing of data, and verified the rationality and validity of the method in this paper through the contrast analysis with site conditions. |
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