Abstract:

In order to analyze the chamber earth pressure of shield tunneling in loess stratum, a numerical model of shield construction is established according to the construction of interval shield tunnel in Xi′an Metro Line 4. Based on the monitoring of the surface settlement at different locations of the model, the surface settlement curves of different monitoring points are converted to the same coordinates for comparison, and the influence of the soil pressure on the unexcavated strata in front of the face is analyzed, and then the method of determining the value of chamber earth pressure is proposed. The results shows that: (1) When the formation in front of the tunnel face is squeezed or insufficiently supported by the shield, the disturbance of the unexcavated stratum will continuously accumulate, and the heave or settlement deformation of the formation in front of the tunnel face will appear with the shield tunneling, which represents that the magnitude and distribution of the settlement curves of each monitoring section are inconsistent. (2) When the chamber earth pressure balances with the water and earth pressure from stratum, the settlement curves of each monitoring section are analogous. For the setting working condition, when the chamber earth pressure is 0. 1 MPa, the ground settlement curves locate in a narrow area, which represents that the pressure value matches the formation.

Key words: shield tunnel, loess strata, chamber earth pressure, numerical analysis