Measurement of earth pressure of shallow buried tunnel with super large diameter and applicability evaluation of calculation method

Based on the Yangzhou Shouxi lake tunnel, the load of segments and structural strain etc of shallow buried shield tunnels with super-large diameters were constantly monitored in the field. Variation rules of earth pressure, and the strain of steel bar were analyzed. Then, the theoretical earth pressures at the segment of the tunnel were calculated based on the overburden load method and Terzaghi's earth pressure method. These theoretical results were compared with the measurement values, analyzing the applicability of different earth pressure calculation methods under different buried depths. The results show that shield rectification has a great impact on the value of tunnel segment load and its spatial distribution, and the impacts lasts until the stability period. The earth pressure on shield segments decreases and tends to be stable gradually after the construction of shield tunnel. The change trend of steel bars' strain is basically the same as the earth pressure, but the former lags behind the latter for reaching the stable state. When the earth pressure reaches the stable state, the measured value is about 48%-60% of the theoretical value. The earth pressure value calculated by the Terzaghi's earth pressure method is much closer to the measured value than that of the overburden load method. Thus, the study in this paper can provide guidance for the load design of shield tunnel segments.