Calculation and Analysis of U-Shaped Shield Thrust and Anti-Force Removal Time

U-shaped shield is the mobile mechanical supporting structure for foundation pit construction in China. In order to rationally design the U-shaped shield and determine the timing of reverse force demolition, the formula and method for calculating the thrust force and the timing of reverse forces removal of the U-shaped shield are analyzed and determined according to the shield construction process and its force mode. The results show that: (1) The earth pressure on both sides of the U-shaped shield is in accordance with the Rankine active Earth pressure theory, and the rationality of the hypothesis is proved by the back analysis of the field thrust test results. (2) The estimating formula for the thrust and the reverse force demolition time of the U-shaped shield design is presented. (3) Combined with concrete engineering, the paper analyzes the reasons for the deviation of the design and the measured value, in order to ensure the redundancy and simplified calculation, it is suggested that the calculation of the active earth pressure and the lateral frictional resistance should be unified according to the 1. 3~ 1. 5 times, and the maximum thrust force according to the calculated value 1. 5 times the design, the equipment capacity is relatively economical. (4) In determining the timing of the reverse force demolition, the U-shaped shield design of the maximum thrust and pipe section and the surrounding friction resistance of the preliminary estimate, and based on the actual thrust of the correction after the determination. (5) The calculation and analysis results can be used as reference for the optimization design and construction of the U-shaped shield in the future.