Research On EPB Shield Foam Injection Rate Optimal Control Under Multi-factors

With the development of underground construction in recent years, Earth Pressure Balance(EPB) shield tunneling method, as a safety and efficient tunneling technique, is becoming a comprehensive way to build the subway. For China having a vast and complex geological conditions, using the foam agents to improve the condition of soil greatly expanded the trial range of the EPB machine. We pay more and more attention on foam soil improvement resently, and the range of applications is becoming wider and wider. As some factors, the researches on foaming agent were focused on the basic performance through laboratory tests. The control method of foam injection rate is according to the worker’s accumulated experiences at the site of construction. The phenomenon of shield-site foam injection too much or too little is inevitable. Especially for complex and volatile formation, the phenomenon is more likely to occur. Taking the security and economic into account, we study the optimal control of the foam injection in this paper. Some achievements were made in the present study as follows:(1) We review a large number of documents to find the technologies about the method of soil improvement for reference. Taking the characteristics of the Northern Heavy Industries Group’s construction project into account, we study and develop the pilot programs.(2) We collect field data (including field test data), and dig deeper relationship between the foam injection rate and the EPB shield tunneling parameters. Ignoring the secondary factor of soil pressure and cutter speed, we study the cutterhead torque variation and driving speed with the amount of foam injection and establish a cutterhead torque model. Finally we designed a scheme of foam injection rate in homogeneous strata.(3) The foaming agent can influence the torque, thrust, and play an important role in improving the tunneling parameters. We derive the formula of torque, thrust, earth pressure and other shield machine tunneling parameters, and carry out the related theoretical analysis. Combined with field data, this article analyzes the factors that affect the foam injection quantity in the composite soil. After collecting the data and analyzing the relationship between the shield machine tunneling parameters under different geological conditions, a new control method of foam injection rate based on multiple factors is proposed in this paper.(4) We apply the artificial intelligence theory on the foam injection rate control. For samples of the shield construction parameters under the composite formationin in Shenzhen, we take the jack thrust, the torque of the cutter, earth pressure, cutter speed, driving speed and other parameters as the input parameters, and establish the foam intelligent control model using Artificial Neural Network to optimize the EPB foam injection quantity.