Measuring annular thickness of backfill grouting behind shield tunnel lining based on GPR monitoring and data mining

Abstract

Ground-Penetrating Radar (GPR) has been widely used in the backfill grouting detections of shield tunnel construction. The proposed approach of automatic annular thickness measurement based on GPR monitoring system and BBP-XGBoost algorithm has been demonstrated to be an effective and efficient technique for detecting the backfill grouting of shield tunnel construction. The advantages include: (1) high accuracy: the proposed model is able to achieve high coefficients of regression R2 (0.943) for training sets and comparatively low RMSE values (0.421 and 1.32 cm) for both training and testing datasets, respectively; (2) high efficiency: the proposed XGBoost algorithm outscores other models in both accuracy and efficiency; (3) real-time output: the trained models were applied to automatically measure the annular grouting thickness of the Tianjin Metro tunnel constructions (China), with consistent real-time outputs for the engineers on site. The proposed approach provides real-time and efficient guidance for the construction of shield tunnels.