Three-dimensional stability analysis of active and passive trapdoors

There has been an increasing interest in the study of sinkhole occurrences due to frequent underground activities. Most of the research direction are related to the detection of the underground cavity using geophysics techniques. Very little is done in the area of soil stability. This paper investigates the three-dimensional stability of circular and square trapdoors. The combined effect of surcharge pressure, soil weight and supporting pressure is considered in Broms and Bennermarks' original stability number for a cohesive soil. The study uses the finite element limit analysis to compute upper bound and lower bound minimum supporting pressures for both collapse and blowout scenarios. The obtained critical stability numbers and factor of safety are compared with other published results in both twoand threedimensions. Design charts, tables and equations are presented to cover a wide range of design parameters and a practical example is introduced to illustrate how to use the them.