Study On The Mechanics Behavior Of Segment Of Interval Shield Tunnel In Metro By Field Test

In order to reveal soil-structure interaction in EPB shield tunneling, the actual groundwater pressure acting on the segment and the distribution of internal force of segments after completion of the tunnel, on the basis of the field test and in combination with the indoor model test and theoretical analysis, this paper has made a study on the mechanical behavior of the segments during the overall construction under the sandy and clayey stratum conditions, analyzed soil-structure interaction in EPB shield tunneling and revealed the distribution regularities of the actual soil pressure and water pressure acting on the main structure of the shield tunnel under the specific construction stratum condition, and draw the conclusions as followings:1. In the design of the single-line metro interval shield tunnel, the control parameter of the upper load over tunnel shall be designed according to the equivalent load of the 1. 5 times external diameter. In the permeable stratum, the calculation of load can be performed using the effective stress method (ground water acting separately from soil); but in case of permeability stratum not to be determined, calculation can be made using the effective stress method and total stress method (ground water being included in soil pressure) respectively and their unfavorable value can be taken as the design control value; In the permeable stratum, the calculation can be performed using the total stress method.2. The stratum properties have a leading effect on load-bearing of segments, so the design and construction of shield tunnel shall be made according to specific properties of stratum;3. The grouting pressure is acting on the segments in short-term, and at the moment when shield segments fall from ring, properly to increase grouting pressure can enhance the axial force of segments, resist the moment effectively and is favorable to the structures;4. The hydramatic Jacking forces behind the shield machine arecomplicated in the process of segments falling from ring, but favorable to the stress of integral structure.The main conclusions above have been applied to the design of segment in Nanjing Metro and can be applied as reference in the other construction of metro in China.