Deformational behaviors of existing three-line tunnels induced by under-crossing of three-line mechanized tunnels: a case study

Abstract

This research presents monitoring data from a complicated case: the under-crossing of new three-line tunnels beneath existing three-line tunnels. The existing tunnels were monitored by electric level and wireless sensing network (WSN). By analyzing the monitoring data, the mutual influence patterns of the new three-line tunnels were identified, and a modified version of Peck’s formula was proposed. Additionally, a correlation between settlement data from the low-frequency electric level and tilt change data from the high-frequency WSN was established. This correlation provided a detailed understanding of the deformation process of the existing tunnels during the under-crossing. The results revealed that the deformation patterns of the existing three-line tunnels during the under-crossing process are similar and could be categorized into three stages. For each stage, a support vector machine prediction model was developed and interpreted using the Shapley Additive explanation method to rank the degree of influence of each construction parameter on the settlement. Grouting volume, shield position, pushing jacks’ pressure, and earth pressure were the main factors influencing the settlement and their importance varied in different stages due to the different relative position of the shield machine to the existing tunnels.