Study On The Long-term Settlement Characteristics Caused By Shield Construction In Ningbo Rail Transit

During the construction of shield tunnel, tunnel excavation causes soil disturbance and ground deformation around the tunnel, and results in the surface settlement. When the ground movement exceeds a certain limit, the structure safety and normal use of surrounding buildings(structures), roads, pipelines will be affected. Therefore, how to predict and control the tunnel settlement becomes an important engineering issue. In recent years, study on the construction technology and deformation characteristics of Ningbo soft soil shield tunnel has been carried out and accumulated a certain amount of achievements. However, study on the long-term settlement characteristics caused by Ningbo soft soil shield tunnel construction has not yet been carried out so far. Therefore, the consolidation settlement problem of Ningbo soft soil shield tunnel still need to be further explored. For this purpose, based on the Ningbo Rail Transit Line 1 project, the paper conducts the study on the surface settlement law and long-term settlement characteristics caused by shield construction, which can provide technical support for the construction and subsequent engineering construction safety as well as how to reduce the impact on the surrounding environment. The main contents of this paper include:1.The surface settlement characteristics of lateral and longitudinal caused by shield construction are analyzed by monitoring the surface settlement caused by shield excavation in Ningbo Rail Transit Line 1 from Wangchun station to Zeming station, selecting the typical cross-section data and combining with the ground conditions of the project. At last, the paper gets the surface settlement law caused by shield construction under the Ningbo soft soil environment.2.Based on the measured data of the typical cross-section, using the origin8.0 software and combining with the experience formula of the traditional prediction methods, the applicability of traditional prediction methods such as Peck formula under the Ningbo soft soil environment is verified.3. The paper simulates the consolidation settlement after shield tunnel excavation by combining with the project of Ningbo Rail Transit Line 1 from Wangchun station to Zeming station and using the program of ABAQUS. The long-term settlement characteristics and change law of pore water pressure caused by shield construction are obtained.