Study and Application of Technique of Synthetic Geologic Prediction Ahead in Safety Construction of Road Tunnel

摘要

There are many unfavorable geological conditions such as fault, water-eroded cave, water gushing, mash gas and coal measures during the construction of road tunnel. They would cause some problems of safety if not dealt with very well. In order to accurately forecast unfavorable geological conditions ahead of the tunnel face and ensure the safe construction of tunnel, many scholars have been studying them from different angles with new technique and methods. Lots of research achievements have been made such as GPR and TSP. However, engineers cannot obtain satisfactory results from various prediction methods. Based on this background, the technique of synthetic geologic prediction ahead (TSGPA) is put forward and established on the research subject of geological disaster prediction of Hebei province. TSGPA is not a simple synthesis with ground geologic measuring, ground penetrating radar (GPR) and Tunnel Seismic Prediction method (TSP), but an embedded and systemic project and method. In this article, the problems such as inaccurate and even wrong geological prediction, which were found during geological prediction, will be discussed, firstly. And then the authors analyze and comment on the three main conventional methods of geological prediction, including their merits and weaknesses. Secondly, the method of synthetic prediction ahead has been introduced. And then, the authors discuss the detailed processes of TSGPA method, which includes two sides, one is about qualitative analysis, and the other is about quantitative analysis. The purpose of qualitative analysis is to acquire primary and total geological information about the tunnel. Quantitative analysis is used to make clear the types of bad geological conditions and to work out their exact locations and sizes, to acquire parameters of rock mechanics such as Youngs modulus and Poisson ratio and so on. The discuss focuses on the application of TSP, back analysis method and FEM. Finally, the author will illustrate the applicability of TSGPA to Guangrenling road tunnel. In this process, two faults were forecasted successfully by the means of TSGPA, and its precision achieves 95%. Therefore, the method of TSGPA is accurate and effective. The purpose of the article is to provide more effective, more scientific forecasting and analyzing methods for tunnel projects.