Lateral Earth Pressure Reduction on High-Filled Cut-and-Cover Tunnels Using Expanded Polystyrene Geofoam and Tire-Derived Aggregate

Abstract: Currently, high-filled cut-and-cover tunnels (HFCCTs) are a practical solution for the prospect of reclaiming valuable usable lands with valleys and the hilly terrain around the world. As a result of the very high backfill soil amount above the HFCCT producing very huge earth pressure, it is essential to use methods of load reduction methods to reduce the earth loads and pressures on the HFCCT, which will increase the safety by reducing the tunnel designing loads. This study is focusing on six load reduction scenarios using expanded polystyrene (EPS) and tire derived aggregate (TDA) in three different forms. The research include using EPS geofoam and TDA in arch and combined horizontal and arch formations as a methods of LEP reduction on HFCCTs which is the first time these methods to be used as methods of any types of loads reduction on HFCCTs. A number of significant factors, including the suggested EPS and TDA forms, the EPS and TDA thickness, and the distance between the bottom of the EPS or the TDA and the top of the HFCCT were studied. The study results determined that a significant LEP reduction on the HFCCTs was achieved, especially with the use of TDA in a horizontal form. Also, model verification made by comparison between the calculated and estimated LEP values on the HFCCT study model using the Rankine equation, Rankine modified equation and Abaqus CAE 2019 software. The calculated and estimated LEP values showed that the calculated value using Rankine modified equation is 23.61% lower than the calculated value using the Rankine equation, which is a high percentage of difference. While the estimated value using Abaqus CAE 2019 is 47.56% higher than the calculated value using the Rankine equation, which is also a high percentage of difference.