Example Analysis Of GPR Images Of Geology Forecast About Loess Tunnel

In the situation of development in infrastructure in our country, the number of tunnels constructed in the loess area of China is increasing. In recent years, the geology forecast is necessary in tunnel engineering, and the most popular method is ground-penetrating radar (GPR). Therefore, we have to face the problem that how to exert the GPR efficiently in the loess area.The thesis introduces the distribution of the loess in China, especially in Shanxi province, as well as the engineering characteristics of loess and the method of constructing tunnel in the loess area. As a kind of special soil, the loess has some special engineering characteristics, for example, its void ratio is high, its quality is non-uniform compact or uniform loose, it has no clear stratification and so on. Those characteristics make the GPR which makes use of the elements of electromagnetic wave emerges have such problems as short forecast distance and difficulty in judging. There is few study of application of the GPR in the loess area all over the world.According to the analysis of shortcomings and advantages and the comparison with other methods, the thesis summarizes the superiority of the GPR, introduces the application principle of the GPR, and analyzes the factors which affect the GPR, for example, the frequency of antenna, the specific conductance and the permittivity.Based on the geology forecast on Taijia highway, according to the comparison with the excavation situation, the effective distance of geology forecast by the GPR is obtained. The GPR with 100MHz antenna can accurately forecast in 12 to 15 meters, and the GPR with 50MHz antenna can accurately forecast in 20 to 25 meters. Meanwhile, the thesis summarizes some classical rock characteristics charactered by images of the GPR and some regularity in geology forecast .The results is instructive to similar engineering in the future.