Force system conversion mechanisms of retaining structures for subway excavation in soft soil

The problem of force system balance between earth pressure and retaining structures has received less attention. Therefore, this paper investigates the force system conversion mechanism of retaining structures for braced excavation in soft soil. Based on the measured data at Daliang Station, the deformation characteristics of braced excavation in soft soil were analyzed, and the temperature correction model and prediction methods for strut force were established. Further, the mechanism of force system conversion between earth pressure and retaining structures was discussed. Optimized support schemes were proposed to reduce the excavation displacement and forces. The results show that the maximum wall displacement was 0.02–0.3% of the excavation depth. The effect of temperature on the support force was about 24.9% on average, and the temperature effect on wall displacement was 12.69–38.57%. The proposed temperature correction model can effectively eliminate the temperature effect on the support force. When excavating to the bottom plate, about 70% of the water-and-soil pressure was converted into the internal force of the support structure. And the optimized support schemes resulted in a maximum reduction in wall displacement of 23.7% and an increase of 4.21% in the proportion of water-and-soil pressure converted into support forces. The results help to provide a reference for the design and construction of the subway excavation engineering.