Volume (14), Issue (1), Year (2026), Pages (69-79)

DOI:10.52113/3/eng/mjet/2026-14-01-/69-79

Research Article By:

Esraa Fakhri Ahmed and Moataz A. Al-Obaydi

Corresponding author E-mail:dralobaydi@uomosul.edu.iq

ABSTRACT

Structures founded on the soil mass encounter stability issues due to cavity that may naturally forms in soluble soil or rock. A significant risk associated with excessive settlement and a reduction in strength of soil.  The coupled behavior of soil, foundation, and structure subjected to seismic loading in the presence of cavities is investigated using 3D-PLAXIS software based on FEM. The study examined the impact of cavity positions on foundation settlement and building deflection. The horizontal distance from foundation center to center of cavity (X) was expressed as a ratio to foundation width (B) (X/B=0, 0.5, 1 and 2), while depth of cavity was expressed as a ratio between vertical distance between foundation base and cavity crown (H) to foundation width (B) of (H/B= 0.067, 0.2, 0.4, 0.8, 1.33 and 2). The results indicated that in case of no-cavity, the settlement increased considerably to 142 mm under seismic load compared to 62 mm under static load, and the differential settlement increased from zero to 11 mm due to seismic load. The risk condition arose when the cavity found under foundation’s edge (X/B=0.5). The maximum total and differential settlements under seismic load were148 mm and 38 mm, which were 4.05% and 245.5% more than in event of no-cavity. Under the limitations of the current study, the influence of cavity on settlement diminished when the cavity offset to location (X≥B) and the effective depth of cavity extended to (H=0.8B). The maximum building floor deflection exhibited when a cavity positioned beneath foundation (X/B=0).

Keywords:

Dynamic load, inter-storey drift, building deflection, Cavity, total settlement, differential settlement.

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