Study on Technique of Foundation Pit for Shield Receiving Shaft of River-Crossing Tunnel in the First Yangtze River's Terrace

In order to provide a reference for other designs and construction of deep foundation pit project of shield receiving shaft with similar engineering geological conditions, taking the shield receiving shaft of the river-crossing tunnel in Wuhan with maximum foundation pit depth of 21.555m for instance, the characteristics of design and construction of the foundation pit with the bracing are presented through analyzing the formation and the engineering geological characteristics in the first Yangtze River's Terrace. Subsequently, the safety and stability of excavating are evaluated by calculating internal force and displacement of the bracing in different working conditions. The results indicate that soils of the first terrace of Yangtze River are of low strength, high compressibility, unfavorable self-stabilization, complicated aquifer and abundant groundwater, based on which the conclusion that the key points in construction are construction of bracing and treatment of aquifer can be obtained. The construction for foundation pit of shield receiving shaft was operated according to the engineering characteristics of the sort of formation, and it is effective to adopt the methods of diaphragm walls with steel shotcrete and dewatering with medium-deep wells.