Influence of backfilling of masonry vault grooves on their load-bearing capacity

In static calculations of stone vaults, backfill is usually considered only as a gravitational load, and its actual interaction with the vault structure is often not taken into account. The object of research is the stress state of stone vaults. The influence of backfill on the load-bearing capacity of stone vaults is analyzed. Methods. A numerical analysis was conducted using the finite element method for vaults with a span of 8.0 m and a thickness of 0.25 m. Two materials for backfilling were considered: sand (E = 120 MPa, density 1500 kg/m³) and expanded clay (E = 15 MPa, density 250 kg/m³). The ratio of the vault height to the span f/L varied from 0.1 to 0.5. Two calculation schemes were compared: taking into account the interaction of the vault with the backfill and without it. Results. It has been found that the inclusion of backfill in the design model reduces the tensile stresses in the vault. The positive effect increases with the ratio of the vault height to the span and is more pronounced for cylindrical vaults than for cross vaults. Sand backfill provides a more significant reduction in stresses due to its higher stiffness, but it also increases the overall load on the vault. The share of the horizontal распорной нагрузки H, perceived by the backfill, reaches 43% for sand and 37% for expanded clay in semicircular vaults (f/L = 0.5). Conclusions. To reduce the static load, it is recommended to use lightweight backfill materials (such as expanded clay), while maintaining a positive interaction with the vault. The effectiveness of lightweight backfill can be improved by using layer-by-layer consolidation with cement mortar or polymer composite reinforcement.

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