Applications And Researches Of Transient Rayleigh Surface Wave Method In Xi'an Ground Fissures

There are a total of 14 ground fissures in Xi'an were found until now. Xi'an ground fissures impede the city's constructions and developments. The explorations and researches of Xi'an ground fissures can help to reduce the damage to the city.Rayleigh has first discovered the Rayleigh wave in 1887. The Rayleigh Wave method has become a brand new method, which can be used in geotechnical, shallow geological and other exploration area. Compared to the conventional existing shallow seismic exploration and drilling methods, this new method is more convenient, effective, labor and money saving.Chapter 1 of this thesis present the purpose of the thesis and the importance of the researching project. Chapter 2 mainly elaborates the elastic constants of the material. From the dynamics of seismic waves aspect, the characteristics of the generation and transmission of the Rayleigh Wave has been fully explained as well. The following chapter introduces the fast knoppof algorithm and the equivalent half-space method. In addition, through combining part of the drilling data, the Xi'an fissure system was modeled to realize tracking the target layers where ground fissure may appear. The inversion chapter introduces the genetic algorithm (GA) and the method combining the equivalent half-space algorithm with inversion. The compare had done between the two algorithms with the forward models. The Chapter 5 is concerned field test. The field data acquisition was carried out with Rayleigh wave method in ground fissure f14, where at Shangtapo village, Chang'an District in Xi'an. Through the analysis of actual data we got the result that it coincided with the actual stratum.In this paper, Rayleigh wave method is first time applied to the exploration of Xi'an ground fissures. We got following results through above researches:1. Fast koppof algorithm and the equivalent half-space method can more accurate to calculate the formation dispersion curve. The advantage of equivalent half-space method is its fast computed speed compared to fast koppof algorithm. Exact inversion results can be obtained through the combination of genetic algorithm with equivalent half-space method.2. Instantaneous Rayleigh surface wave method could accurately inverse the depth and thickness of ancient soil stratal. It can assist or replace drilling to definite the location and shape of ground fissures in Xian.3. If the relevant inversion parameters are appropriate, accurate shear wave velocity can be obtained by instantaneous Rayleigh surface wave, providing a reliable foundation for the in situ test and ground division of geotechnical engineering.