Assessing the stresses and magnitude of plastic hinge in a tunnel conduit made of precast metal corrugated structures taking into account the soil backfill parameters

Abstract

The object of research is a tunnel conduit made of star-shaped metal corrugated structures. The stresses and magnitude of the plastic hinge occurring in the metal corrugated structures of the tunnel conduit were investigated, taking into account the degree of compaction and the height of the soil backfill. It was established that when the height of the backfill above the tunnel conduit made of precast metal corrugated structures increases and the degree of compaction of the soil backfill decreases, there is an increase in the values of stresses and plastic hinge in metal structures. With the height of the backfill above the conduit equal to 2.75 m and the degree of compaction of the soil backfill RP=80 %, stresses of 235.89 MPa are reached, exceeding the permissible 235 MPa. At the same time, the value of the plastic hinge is 1.03, which exceeds the normative 1.0. It was established that at embankment heights above the tunnel conduit structures from 1.75 m to 2.0 m, the smallest difference in stresses and magnitude of the plastic hinge is observed. At RP=98 %, the stress difference is 0.66 MPa, and the value of the plastic hinge is 0.008. In the case of the height of the embankment above the conduit from 1.5 m to 1.75 m, the stress increase was 5.5 MPa, and the value of the plastic hinge – 0.031. When the embankment height increases from 2.0 m to 2.25 m, the stress difference is 7.57 MPa, and the value of the plastic hinge is 0.041. It was determined that when the height of the embankment above the conduit was increased by 1.0 m in the range from 0.75 m to 1.75 m, the stress difference at RP=98 % increased by 27.84 MPa. However, when the height was increased by 1.0 m in the range from 2.75 m to 3.75 m, the stress difference increased by 12.66 MPa. At the same time, the value of the plastic hinge at embankment heights from 0.75 m to 1.75 m increased by 0.139, and at embankment heights from 2.75 m to 3.75 m – by 0.093