Real-time laser scanning for conditioned coarse-grained soil monitoring on conveyor belt in earth pressure balance shield

To address the hysteresis in assessing the workability of conditioned soils and the inefficiency in estimating the soil volume flow rate in tunnelling practice, a novel real-time assessment and monitoring approach was proposed. Based on laser scanning technology and point cloud data analysis, the approach can monitor the workability and the volume flow rate of conditioned soils on the horizontal conveyor belt of an earth pressure balance (EPB) shield in real-time. Firstly, the accuracy of laser scanning measurements was verified by comparing manually measured slump and spread values with laser scanning results. Then, a series of model tests for scanning the coarse-grained soils with different conditioning parameters and belt speeds on the horizontal conveyor belt were performed. The appropriate ranges of secant angle and unevenness of soil cross-sectional profile were obtained for assessing the workability of conditioned soils. The volume flow rate was calculated by integrating the cross-sectional areas of conditioned soils. Finally, the proposed approach was successfully applied in identifying the workability of conditioned soil and its discharge rate in the EPB shield tunnelling project. This study contributes to the real-time monitoring of conditioned soils on the horizontal conveyor belt and provides practical insights for the optimal management of EPB shield tunnelling.