| The tunnel geological hazard forecast is an important insurance in tunnel construction. Nowadays, there are various methods for tunnel geological hazard forecast; especially the tunnel seismic prediction method is widely used because of its great precision and long range. TSP (tunnel seismic prediction) is the mainly representation based on reflection wave exploration. Some papers indicates this kind of equipment's acquisition cost and cunning cost is high, its data processing is not flexible enough, and also has bias in the prediction result of gently inclined geological interface. Therefore, we should make further study on tunnel seismic prediction theory and the characters of reflected waves from any direction, to improve the accuracy of geological forecast, these problems need to be solved urgently.Because of the complexity of geological conditions, only by using ground geological exploration method is difficult to determine the situation of tunnel geology disaster may be encountered in the process of construction. Tunnel geological hazard prediction is operated on the sidewall of tunnel; it has higher precision than surface geological exploration. By using three-component geophone, we can receive seismic signals disseminate from three-dimensions geological space. So we can obtain more information of reflected waves to enhance the accuracy of prediction. During data acquisition process, receiving P-wave and S-wave information with high SNR (signal to noise ratio) is the premise and the foundation of making accurate geology disaster prediction, and also the separation of reflected waves and depth migration of reflectors are the key to improve the accuracy of seismic tunnel prediction.Base on elastic and physical characteristics of rocks (rock body), by using staggered-grid finite-difference method, we studied the reflected wave propagation characteristics of reflectors witch are differ from interface dips. By analyzing the characteristics of reflected wave we can get the following conclusions: the apparent velocity of reflected wave comes from reflector of steep dip angle (large than 45 degrees) is negative, and the energy of S-wave occupies the superiority in Z-component, and P-wave occupies the superiority in X-component. When the reflector's dip angle is less than 45 degrees, the apparent velocity is positive versus the offset increases. The apparent velocity of reflected waves which come from reflector behind the tunnel face is always positive. To master these propagation rules of the reflected wave coming from the different reflectors with different dip angles is significant of the offset design and improvement of geophysical prospecting interprets accuracy.According to the special requirements of construction environment, we have designed a tunnel seismic prediction data acquisition system with large dynamic range and broadband. This acquisition system has signal input terminals for speed and acceleration. We also designed a kind of acceleration sensor and a speed sensor. This kind of speed sensor can be directly installed in naked hole without special casing pipe. And it also has good direction sensitivity, so we can get good handling effect using polarity analysis to separates P-wave SH-wave and SV-wave. That makes this technology has the more superiority in thrift test cost and raising test efficiency. During data acquisition process, the principle of choosing minimum trace clearance is to efficiently avoid the space aliasing. And according to the frequency property of explosive source to choose charge quantity, and choosing high detonating velocity charge, in order to get the best survey effect with the most economic, safe charge quantity.The data processing has fully considered the effects of reflected wave characteristic in tunnel. So we take multi-wave multi-component seismic exploration principles as foundation, adopt spherical proliferation compensation, inverse Q filtering, wave field separation and depth migration of reflectors.The purpose of tunnel seismic prediction is to predict the geological structure and lithologic characteristics ahead of the tunnel face. Deduced the reflection time-path curve equations of single interface and the interface between parallel multilayer media, and calculate some model curve to summarize the feature of reflections in this recording geometry. According to the analysis of above we use high high-resolution linear Radon transformation to separate the useful wave from the disturbed seismic data. In order to separate reflected wave of little dip angle geology interface, we designed a rectangle window to keep the significative reflected wave. The mathematic model process proved that this method could get rid of useless signal and noise efficiently and it is a very powerful process method.Another important data process technique is called depth migration. Its function is to convert signals in time domain to depth domain by according velocity analysis result. In this paper we introduced a new method called vector Fresnel-volume Kirchhoff migration of multi-component data. The method is tested on a synthetic seismic with strongly limited aperture. Migration artifacts reduced compared with standard migration schemes. And by using it we can get the geologic interpretation profile, to satisfy the goal of geological prediction.Through carefully studying of the construction environment and characteristics, we made a portable data acquisition system (including a seismic data acquisition system, three-component geophones and a blaster system) and a data processing software which can deal with entire space seismic wave to meet the challenge of getting the information of hazards structure as quickly and accurate as possible. In tunnel geological hazards prediction, there is no universal method that can solve all the problem of geological survey in exceptionally complex geology condition. In the region has complex geological condition, we should spend more time and means in the investigation, because any misjudgement may cause irretrievable losses.
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