Three-Dimensional Stability Investigation of Trapdoors in Collapse and Blowout Conditions

Road-related sinkholes are of great concerns nowadays, appearing frequently in media stories. In the undrained stability analysis, a dimensionless stability number that is known as Broms and Bennermark's original stability number expresses the combined effect of surface surcharge pressure, self-weight of the soil, and the supporting pressure. This "critical" undrained stability number, N-c, is used in this paper to formulate three-dimensional (3D) upper-bound and lower-bound solutions in active (collapse) and passive (blowout) scenarios of sinkhole stability using the classic trapdoor problem. Design charts, tables, and equations were developed to cover a wide range of practical design parameters. Together with modern geophysics techniques for the detection of underground cavity as well as the findings of the associated failure patterns in this paper, the study should, therefore, be of value to practitioners in their daily decision making.