Study On The Cross-well Wave Tomography And Its Application

With the depth of China's reform and opening up, especially in the current global economic crisis is not yet clear, our construction of a large number of civil engineering, and investment trends continue to increase. In these works the process of design and construction to the basis of investigation, the basis of the construction, testing and governance projects for the purpose of detecting numerous drilling.The traditional methods are very difficult to satisfy the request of fine structure exploration in engineering geological survey works. Such as single-borehole, cross-borehole probing, resistivity well logging and self-potential well logging, only can reflect a few effect around the hole-wall, and outside the opening wall structure can only be carried on the extrapolation. Since the nineties, the cross-well wave tomography entered the practical stage gradually, which has the incomparable superiority that sole borehole survey methods don't have, and it reflects the geological characteristics of cross-section between two drillings, which is the area survey, therefore this method can make good effect in exploring the unusual body of project, such as collapse columns, fissures, cracks, fracture zone, soft interlayer, empty or unknown underground structures and so on. At the same time, the cross-well wave tomography has the following advantages: (1) high- frequency, then the ability to distinguish is strong; (2) because of anti-low-frequency interference, it can be used for work area with outside interference; (3) this method has the observing systems to record direct wave, so it can reflect the non-homogeneous geological body more sensitively.This dissertation begins to analyze the actuality of sound wave computer tomography at home and abroad. First of all, this dissertation briefly illustrates the physical property of sound wave and its basic principle when it disseminates in the underground media; secondly, the paper briefly introduces the inversion technique of sound wave computer tomography, and start with the solution methods how to effectively solve the large sparse matrix equation, which is the key issue of computer tomography, discusses in detail the basic algorithms: the singular value decomposition (SVD), the simultaneous iterative reconstruction technique (SIRT), the conjugate gradient least squares (CGLS) and the least square QR dissolution (LSQR), and makes these basic algorithms for the executable programs, then makes them for algorithm testing, special matrix testing and actual matrix testing. The algorithm testing is to test the correctness in theory, the special matrix testing is to determine the stability of algorithm program, the actual matrix testing is to evaluate the result in practical application, so we can compare the various algorithms; Finally, two practical demonstrations are given to illustrate the ability to find potential object by sound wave computer tomography, and make good evaluation to the objects (concrete and rock) which test in actual.