Coupled effect of tire-derived aggregate and geogrid on lateral earth pressure on high-filled cut-and-cover tunnels

For the possibility of using valuable lands with plateaus terrain, the High-filled cut-and-cover tunnels (HFCCTs) are considered a practical and successful solution. The HFCCT is first constructed and then backfilled in layers in the trench, which is different from traditional tunnel construction methods. Because the high amount of backfill soil above the HFCCT produces ultrahigh earth pressure, it is necessary to use load reduction methods to reduce the earth pressure on the HFCCT, which will reduce the tunnel designing structure loads and increase safety. This study describes two load reduction methods using a combination of tire-derived aggregate (TDA) and geogrid. Abaqus CAE 2019 software, based on the finite element method, was employed to analyze and examine the lateral earth pressure (LEP) reduction progress and mechanism. Several influential factors, including the geogrid presence effect, the TDA form, the TDA thickness, and the distance between the top of the HFCCT and the bottom of the TDA were studied. The analysis results focused on changes in average LEP, relative vertical displacement of the HFCCT backfill soil prisms, and the effect of geogrid presence on the top of the TDA. This study found that the factors are influential and have significant effects on the average LEP reduction on the HFCCT through the load reduction mechanisms, which include relative vertical displacements of the HFCCT backfill soil prisms and soil arching, where the average LEP on the top of the HFCCT model reduced from 303 kPa to 125 kPa (58.745% reduction in the average LEP).