A specific energy and penetration interaction-based method for optimizing TBM operational parameters in hard rock

Abstract

The timely and appropriate adjustment of operational parameters is necessary for efficient tunneling and hazard prevention in TBM projects. However, the currently provided operation control strategies mainly tend to adjust the operational parameters by TBM driver to achieve the maximum penetration, which leads to severe cutter wear in hard rock tunnels. This study innovatively uses tunnel specific energy (SE_TBM) to quantitatively describe the wear state of cutting tools, and proposes a quantitative optimization strategy for operating parameters based on the specific energy and penetration (SE_TBM-P) interaction relationship. A comprehensive database of TBM performance containing 219 tunnel intervals was compiled based on five tunnel projects from China, which covered the rock properties, TBM specifications and operational parameters necessary for performance optimization. The mapping relationship between tunnel specific energy and penetration for different rock types and rock mass properties was investigated in detail, and a standardized field penetration index (SFPI) characterizing only the rock mass properties was proposed. Subsequently, a new empirical prediction model for normalized disc cutter thrust was developed using the SFPI. Based on this, a parameter optimization procedure based on SE_TBM-P interaction diagram is constructed by taking into account various operational constraints of cutter load capacity, cutterhead torque limitation, and cutter assembly geometry restriction. It can maximize advance rate and minimize downtime under the influence of different RPMs of TBM. Finally, the proposed parameter optimization method is implemented in two recent tunnel projects to verify its effectiveness. This method can overcome the TBM drivers’ subjectivity and provide a quantitative prediction for the optimum tunneling strategy in hard rock TBM.