Deformation of large-diameter pipeline induced by double shield tunneling in silty fine sand strata

This paper investigated the deformation of a large- diameter pipeline caused by double shield tunnel construction in silty fine sand strata inNantong, China, by on- site measurements and numerical simulations. Results indicate the pipe settlement curve was not symmetrical after the double tunnel construction in the silty fine sand strata. The construction of the subsequent tunnel had a significantly smaller impact on the stress and horizontal displacement of the pipeline than the preceding tunnel. There is a significant shading effect of the large- diameter pipeline, which would restrict the soil settlement above the pipeline. The adjusted settlement formula shows good agreement with the measured data, facilitating approximate calculations for both surface and pipe settlements. The correction factor a ranges from 0.50 to 0.90, while b ranges from 0.95 to 1.20.The elastic modulus and the burial depth of the pipeline had a great effect on the stress of the pipeline, but a smaller effect on its settlement. However, the soil loss rate greatly affected both the settlement and stress of the pipeline. Moreover, the pipeline risk level distribution map can quickly identify the risk status of the pipeline.