Estimating locations of soil–rock interfaces based on vibration data during shield tunnelling

This paper proposed an approach for estimating the locations of the soil–rock interfaces (SRI) based on vibration data during shield tunnelling. Vibration data were collected using accelerometers installed on the back of the soil chamber wall. The continuous wavelet transform (CWT) was then employed to analyse the features of the time-frequency spectrum of acceleration in various formations, which was used to identify vibration peaks and its cycle. Moreover, the key factors (installed radii of disc cutters and the locations of the SRI) influencing the acceleration peak amplitudes were determined based on the process of disc cutters colliding with the SRI. An equation was proposed to establish the relationship between the locations of the SRI and the interval time of the vibration peaks corresponding to the disc cutters, which can be applied to estimate the SRI during shield advancement. The proposed approach was applied to the Guangzhou-Foshan intercity railway project and validated by comparing the obtained SRI with a linearly connected SRI using a geological survey and the geological characteristics identified by fuzzy C-means (FCM).