Experimental investigation of the effect of using expanded polystyrene geofoam and geogrid in different forms on vertical earth pressure on high-filled cut-and-cover roadway tunnel

Abstract

Using high-filled cut-and-cover tunnels (HFCCTs) can provide a practical and ideal solution for the possibility of using highly demanded lands with plateaus terrain. The huge amount of HFCCT backfill soil produces ultrahigh vertical earth pressure (VEP). Therefore it is necessary to use load reduction methods and mechanisms to reduce the VEP on the HFCCT, which will reduce the risks and increase safety by reducing the tunnel designing loads. This experimental study describes methods of VEP reduction on the HFCCTs using expanded polystyrene (EPS) geofoam as a compressible material in two different forms without and with the presence of geogrid on top of the EPS. Several important factors, including the effect of geogrid presence on top of the EPS, the EPS form, the EPS thickness, and the distance between the bottom of the EPS and the top of the HFCCT discussed and studied. It determined from the study results that the mentioned factors have significant effects on the VEP reduction on the HFCCTs through their roles in the VEP reduction mechanisms. This study adopted two VEP reduction mechanisms; relative vertical displacements of the HFCCT backfill soil prisms and soil arching. The mentioned two mechanisms caused a significant reduction in the VEP on the top of the HFCCT, where the best result was a 76.0% reduction in the VEP on the HFCCT.

Keywords:

• High-filled cut-and-cover tunnels
• vertical earth pressure reduction
• expanded polystyrene geofoam
• geogrid

Reviewing Editor:

• Sanjay Kumar Shukla
• Edith Cowan University
• Australia

SUBJECTS:

• Civil, Environmental and Geotechnical Engineering
• Geomechanics
• Soil Mechanics
• Tunnelling & Underground Engineering Geomechanics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The manuscript has no associated data.

Additional information

Notes on contributors

Mohammad Hajiazizi

Mohammad Hajiazizi holds a Ph.D. in Geotechnical Engineering from the University of Shiraz, an M.Sc. in Geotechnical Engineering from the University of Tarbiat Modares, and a B.Sc. in Civil Engineering from the University of Tabriz, Iran. As an Associate Professor in the Civil Engineering Department at the Faculty of Engineering, Razi University, Iran. His research interests span a wide spectrum within Geotechnical Engineering, including Numerical Modeling, Computer Codes for Geotechnics, Machine Learning in Geotechnics, Physical Modeling in Geotechnics, Laboratory Tests in Static and Cyclic States, and Slope Stability Analysis in Rock and Soil Mechanics. Dr. Hajiazizi has authored over 70 papers published in esteemed journals in Geotechnical engineering, including ASCE, Elsevier, Springer, and Taylor, among others. Additionally, he has actively participated in more than 30 national and international congresses, showcasing his commitment to advancing the field through scholarly discourse and collaboration.