Tunnelling-induced ground deformation subjected to the behavior of tail grouting materials

The deformation of tail grouting plays an essential role in the settlement control of shield tunnelling, which has not been visualized in construction. The conventional methods can only evaluate the quality of tail grouting by the calculating deformation of ground surface, and the mechanism of grouts deformation under the earth pressure is not yet understood in construction. In this study, a novel lab apparatus is designed to explore the mechanism of grouts deformation in respect to the behavior of grouting materials. The purpose of lab tests is to visually analyze the behavior of grouting materials and to investigate the mechanism of grout consolidation induced by varying proportions of grouts and earth pressure. The XRD (X-ray diffraction) and SEM (Scanning Electron Microscope) analysis is used to reveal the micromechanics of the deformation and strength of grouts. Based on laboratory tests results, the parameters of the displacement convergence method are calibrated to optimize numerical analysis. The comparison of results of the proposed method with those obtained by analytical methods and equivalent layer method shows the high performance of the proposed method. The parameters of the proposed numerical method are derived through laboratory tests as opposed to empirical estimations, which could result in more accurate predictions of ground deformation. By comparing the predicted surface settlement to measured data, the Beijing Metro Line 12 project verifies the adaptability of the proposed method.