This study focuses on the behaviour of buried gas pipelines subjected to surface loading. The study is oriented towards an experimental campaign carried out on small-scale pipelines, with three different wall thicknesses, both in monotonic and cyclic conditions. Pipes have been instrumented with strain gauges and inner displacement sensors, allowing to record deformations, stresses and ovalisation of the pipe, in addition to the load-settlement relationship at the soil surface. Results show that the presence of the pipe affects the global soil response (stiffness and bearing capacity). Analysis of the strain distribution and pipe deformed shape indicate that the pipe response is complex, with no symmetry along the horizontal axis, and a heart-shaped deformation pattern. The pipe rigidity affects the local behaviour at the pipe level (displacement pattern, evolution of stresses during cyclic loading and increasing lateral support). Classical pipeline design theory has been assessed based on the experimental observations, invalidating several underlying hypotheses.

The effectiveness of load-reduction techniques often diminishes due to creep behavior observed in geomaterials, as loess backfill is used, the load reduction rate of high-filled cut-and-cover tunnels (HFCCTs) after creep will decrease by 10.83%, posing a threat to the long-term stability of deeply buried structures such as HFCCTs. Therefore, a geotechnical solution is crucial to ensuring sustained effectiveness in load-reduction strategies over time. This study utilizes a finite-difference method to examine three promising measures for mitigating creep effects. Our analysis focuses on the time-dependent changes in earth pressure atop the cut-and-cover tunnel (CCT) and the internal distribution of cross-sectional forces, including bending moment, shear force, axial force, and displacement. Results indicate that the creep behavior of load-reduction materials significantly influences the internal force distribution. Furthermore, sustained load reduction is achieved when utilizing low-creep materials like dry sandy gravel as backfill soil, which needs to be borrowed from other sites. Additionally, integrating concrete wedges with load-reduction techniques facilitates a more uniform stress distribution atop CCTs.