A Geological Prediction System for Shield Construction Based on Focusing Frequency IP Method

In view of the problem of excavation space closed and difficulty in geological prediction during shield construction, a method of advanced geological prediction based on focusing current method and frequency domain IP method is designed, which can realize transmission and effective reception of detection current under low power. In order to improve the measuring accuracy and stability, the current measuring coil is introduced to focus the current effectively, and the under-focusing and over-focusing problems are solved. In this paper, the principle and advantages of the focused current method and the frequency domain IP method are introduced. At the same time, a two-dimensional axisymmetric model of the 6 M class EPB shield machine is established, and the theoretical sounding depth is calculated. According to the geological prediction method studied in this paper, the system is specially designed for the EPB shield machine used for the No.08 of Dalian Metro Line 5 (Houyan Station-Houguan Village station) to realize the application of focused current method and frequency domain IP method in the shield machines and the real-time prediction in the construction process. Through the analysis of the prediction results and the continuous verification in the construction process, the method has basically achieved the expected goal and realized the accurate prediction of the unfavorable geological conditions in front of the tunnel face for many times, which makes it of great value for promotion and application.