Experimental and Numerical Analyses for Earth Pressure Distribution on High-Filled Cut-and-Cover Tunnels

Abstract

The use of high-filled cut-and-cover tunnels (HFCCTs) provides an ideal solution for reclaiming usable land in northwestern China because of the unique landforms of the Loess Plateau. Different from traditional tunnel boring methods, the HFCCT is first constructed and then backfilled in layers in the trench. Due to the backfill above the cut-and-cover tunnel (CCT) is required in quantity, currently, the existed estimating methods of the earth pressure may not suit the high-filled constructions. The ability to estimate the load on such tunnels and high backfill projects is extremely important. Conceptually, the Marston-Spangler (M-S) theory for buried culverts may be used to estimate earth pressure on HFCCTs. However, the earth pressure would be quite different from that of buried culverts in terms of the backfill volume, cross-sectional shape of structure, and foundation conditions. This paper presents physical experiments and numerical investigations to verify the influence of cross-sectional shape (arch and rectangle) of CCTs, foundation settlement, and load reduction using expanded polystyrene (EPS) for the vertical earth pressure (VEP) distribution and vertical displacement around a CCT. The experimental results agree well with the numerical analysis results. Moreover, further comparisons were also made to analytical analysis based on M-S theory. The comparison results indicate that analytical solutions for buried culverts cannot be applied to HFCCTs directly. In order to obtain the earth pressure accurately, designers must consider many influential factors.