Experimental and Numerical Investigation on Contributing Factors of Near-Surface Sinkhole Formation

Abstract

Sinkholes caused by natural or anthropogenic factors pose potential safety hazards in urban areas. This study investigates the failure mechanism of seepage-induced sinkholes due to defects of underground pipelines through physical experiments and numerical simulations. Two sets of experiments with different soil types were conducted with surface displacements monitored during the initiation and development processes of the sinkholes. An improved single layer soil-water coupled smoothed particle hydrodynamics (SPH) method, which dynamically detects changes in the free surface and boundaries around the underground opening, is introduced to simulate these experiments and to explore underlying mechanism. Both the experimental results and numerical study indicate that an underground cavity could form and be sustained in soils with high shear strength that is attributed to cohesion or apparent cohesion arising from capillary effect, eventually resulting in a sudden collapse; while weaker soils could not sustain a sizable cavity and gradual surface displacements occur. To further reveal the mechanisms behind these observations, a parametric study is conducted by considering variations of mechanical and hydraulic properties of the soils. A simple quantitative framework is then proposed to characterize the various types of sinkholes.