Effect of the circular cavity on the undrained bearing capacity of shallow strip footing

Abstract

Underground cavities such as aqueducts, karsts, wells, and tunnels in the vicinity of the footing have significant effects on its bearing capacity. In the present study, the undrained bearing capacity of strip footing above single and twin cavities in clay is investigated using numerical modeling using the Plaxis 2D. The curves are presented as a dimensionless function concerning vertical and horizontal distances from the footing, cavity radius, and distance between twin cavities for rigid and heterogeneous soil to assess the undrained bearing capacity factor. The results show that with increasing the vertical and horizontal distance of the cavity from the footing, the undrained bearing capacity factor increases. Accordingly, at a certain vertical and horizontal distance (respectively ${\alpha }_{cr} \mathrm{and} {\beta }_{cr}$), the bearing capacity reaches a certain and constant value, and at greater distances, the bearing capacity factor of the footing is independent of the cavity. Also, as the cavity size increases, the bearing capacity factor of the footing decreases. Displacements due to the presence of underground cavities have significant effects on the stability and bearing capacity of the shallow footing. These displacements occur by three mechanisms of ceiling, wall, and combined ceiling and wall failure.