Evolution and Controlling Mechanisms of Soil Arching in Heterogeneous Layered Ground Under Deep Burial Conditions

Soil arching governs load redistribution around underground openings, yet its progressive development in deeply buried layered ground remains insufficiently quantified. This study uses a two‐dimensional finite‐element active‐trapdoor model, validated against published experiments, to compare six homogeneous soils and 57 layered profiles (63 cases in total) containing two to six layers. The results showed that homogeneous ground exhibited three distinct deformation zones, namely a primary displacement zone, a transition zone, and an essentially undisturbed zone, with surface settlement increasing approximately linearly with trapdoor displacement. In layered ground, stiffness and strength contrasts deflected the displacement field, particularly in the selected three‐ and four‐layer profiles. Trapdoor stress evolved in two stages: rapid initial redistribution followed by a slower approach to a quasi‐steady response. Soil arching in homogeneous ground was controlled mainly by stiffness and shear strength, whereas the layered responses depended strongly on stratigraphic sequence and the properties of the material above the trapdoor. Profiles containing more mud retained a larger fraction of the initial trapdoor load, and the number of layers alone did not produce a monotonic response. Stress relief above the trapdoor was accompanied by stress concentration in the adjacent stationary ground; the affected zone extended approximately 30–40 m (3–4B) above the trapdoor, with peak stress concentration occurring within 0.10–0.18B above the trapdoor. For most heterogeneous cases, soil arching ratio ranged from 0.21 to 0.37 and the maximum settlement magnitude ranged from 0.17 to 0.21 m. The results showed that stratigraphic arrangement and near‐trapdoor properties were more informative than the number of layers alone for assessing arching in deeply buried layered ground.