Fig 1.
Schematic diagram of strata subsidence and pipeline bending deformation.
The red line DC represents the buried pipeline, and it is divided into four sections according to the strata deformation.
Fig 2.
Finite element models of the soil and buried pipeline.
(a) Finite element model of the buried pipeline. (b) Finite element model of the strata, and it is divided into two blocks. (c) Cross section of the whole model.
Fig 3.
Stress-strain curves of X65 and X80.
Relationship of stress and strain of the two buried pipeline materials.
Fig 4.
Deformations of the strata and buried pipeline.
Deformations of the hole wall in the subsidence strata and no-subsidence strata are different.
Fig 5.
Longitudinal strain and equivalent plastic strain of DA pipeline.
(a) Longitudinal strain of DA section pipeline. (b) Equivalent plastic strain of DA section pipeline.
Fig 6.
Bending deformations and cross section shapes under different subsidence.
(a) Bending deformation of the buried pipeline. (b) Cross section shape of the most dangerous part of the buried pipeline.
Fig 7.
Cross section shapes of the pipeline before and after failure.
(a) Circular cross section of the new pipeline. (b) Elliptical cross section. (c) Crescent cross section.
Fig 8.
Longitudinal strain curves under different subsidence.
Dotted line represents the boundary between the settlement and no-settlement strata.
Fig 9.
Out of roundness, longitudinal strain and equivalent plastic strain curves under different subsidence.
Out of roundness k, longitudinal strain εx and equivalent plastic strain εp change with the increasing of strata subsidence.
Fig 10.
Deflection curves of buried pipelines under different diameter-thickness ratios.
The deflection curve comes from the displacement of the nodes in the neutral surface for the buried pipeline.
Fig 11.
Out of roundness, longitudinal strain and equivalent plastic strain curves under different diameter-thickness ratios.
Diameter-thickness ratio D/t affects the bearing capacity and mechanical strength of the pipeline.
Fig 12.
Bending deformation of buried pipelines under different buried depths.
Deformation of buried pipeline decreases with the increasing of buried depths.
Fig 13.
Deflection curves of buried pipelines under different buried depths.
Buried depth has a great effect on the buried pipeline in subsidence strata, but has a small effect on the other section.
Fig 14.
Out of roundness, longitudinal strain and equivalent plastic strain curves under different buried depths.
Out of roundness k, longitudinal strain εx and equivalent plastic strain εp change with the increasing of the buried depth.
Fig 15.
Deflection curves of buried pipelines under different internal pressures.
Buried pipeline with different pressures (0~ Pmax) was investigated.
Fig 16.
Out of roundness, longitudinal strain and equivalent plastic strain curves under different internal pressures.
Internal pressure can enhance the ability of resistance to deformation for the buried pipeline, out of roundness k, longitudinal strain εx and equivalent plastic strain εp can be affected by the internal pressure.
Table 1.
Results under different friction coefficients.
Table 2.
Physical parameters of soils.
Fig 17.
Deflection curves of buried pipelines under different soils.
Buried pipelines under loess strata, sand strata and clay strata were investigated.
Table 3.
Pipeline strains under different soils.